Bug Fixes:
* Allow [, #, and space as the first character in database names. (Reviewed by Stefan Fercot, Cynthia Shang. Reported by Jefferson Alexandre.)
* Create standby.signal only on PostgreSQL 12 when restore type is standby. (Fixed by Stefan Fercot. Reviewed by David Steele. Reported by Keith Fiske.)
Features:
* Expire history files. (Contributed by Stefan Fercot. Reviewed by David Steele.)
* Report page checksum errors in info command text output. (Contributed by Stefan Fercot. Reviewed by Cynthia Shang.)
* Add repo-azure-endpoint option. (Reviewed by Cynthia Shang, Brian Peterson. Suggested by Brian Peterson.)
* Add pg-database option. (Reviewed by Cynthia Shang.)
Improvements:
* Improve info command output when a stanza is specified but missing. (Contributed by Stefan Fercot. Reviewed by Cynthia Shang, David Steele. Suggested by uspen.)
* Improve performance of large file lists in backup/restore commands. (Reviewed by Cynthia Shang, Oscar.)
* Add retries to PostgreSQL sleep when starting a backup. (Reviewed by Cynthia Shang. Suggested by Vitaliy Kukharik.)
Documentation Improvements:
* Replace RHEL/CentOS 6 documentation with RHEL/CentOS 8.
Update RHEL/CentOS 7 to cover the versions that were previously covered by RHEL/CentOS 6.
Since RHEL/CentOS 7/8 work the same update the documentation logic and labels to reflect this compatibility.
Inaccuracies in sleep time or clock skew might make a single sleep insufficient to reach the next second.
Add a few retries to make the process more reliable but still avoid an infinite loop if something is seriously wrong.
Refactor the code to allow a dynamic number of indexes for indexed options, e.g. pg-path. Our reliance on getopt_long() still limits the number of indexes we can have per group, but once this limitation is removed the rest of the code should be happy with dynamic numbers of indexes (with a reasonable maximum).
Add an option to set a default in each group. This was previously handled by the host-id option but now there is a specific option for each group, pg and repo. These remain internal until they can be fully tested with multi-repo support. They are fully tested for internal usage.
Remove the ConfigDefineOption enum and use the ConfigOption enum instead. They are now equal since the indexed options (e.g. cfgOptRepoHost2) have been removed from ConfigOption.
Remove the config/config test module and add required tests to the config/parse test module. Parsing is now the only way to load a config so this removes some redundancy.
Split new internal config structures and functions into a new header file, config.intern.h. More functions will need to be moved over from config.h but that will need to be done in a future commit to reduce churn.
Add repoIdx to repoIsLocal() and storageRepo*(). Multi-repository support requires that repo locality and storage be accessible by index. This allows, for example, multiple repos to be iterated in a loop. This could be done in a separate commit but doesn't seem worth it since the code is related.
Remove the type parameter from storageRepoGet(). This parameter existed solely to provide coverage for the case where the storage type was invalid. A better pattern is to check that the type is S3 once all other types have been ruled out.
Improve locking on remote processes by introducing an exec-id that is unique to the main process and passed to all remote processes. This allows the remote processes to determine if a lock is held by a remote from the same main process. If so, the lock is allowed.
The exec-id is also useful for associating remote logs with main logs for debugging purposes.
When restore type standby is provided, the recovery.signal isn't needed and may lead to some confusion (see #1236).
Lately, when using pg_basebackup --write-recovery-conf, only the standby.signal file is created. This change would then align with that behaviour.
Return a path missing error when a stanza is specified for the info command but the stanza does not exist in the repository.
Previously [] was returned, which is still the case if no stanza is specified and the repository does not exist.
lstRemoveIdx(list, 0) resulted in the entire list being moved down to the first position which could take a long time for big lists. This is a common pattern in backup/restore when processing file queues.
Instead simply move the list pointer up when first item is removed. Then on insert check if there is space at the beginning when there is no longer space at the end and do the move then. This way if a list is built and then drained without any new inserts then no move is required.
There were a number of places in the code where "hostId" was used, but hostId is just the option group index + 1 so this led to a lot of +1 and -1 to convert the id to an index and vice versa.
Instead just use the zero based index wherever possible. This is pretty much everywhere except when the host-id option is read or set, or where a message is being formatted for the user.
Also fix a bug in protocolRemoteParam() where remotes spawned from the main process could get process ids that were not 0. Only the locals should spawn remotes with process id > 0. This seems to have been harmless since the process id is only a label, but it could be confusing when debugging.
iniLoad() was trimming lines which meant that a leading space would not pass checksum validation when a manifest was reloaded. Remove the trims since files we write should never contain extraneous spaces. This further diverges the format for the functions that read conf files (e.g. pgbackrest.conf) and those that read info (e.g. manifest) files.
While we are at it also allow [ and # as initial characters. # was reserved for comments but we never put comments into info files. [ denotes a section but we can get around this by never allowing arrays as values in info files, so if a line ends in ] it must be a section. This is currently the case but enforce it by adding an assert to info/info.c.
WAL timeline history files were not being expired because they were small and generally not very plentiful.
However, in some cases large numbers of history files may be generated so it makes sense to remove useless history files to keep things tidy.
The history file for the oldest retained timeline is kept for debugging purposes even though it is not used for recovery.
Instead of using memmove() to manage the internal output buffer for every small read, track the current buffer position and only move data when the small read cannot be satisfied and more data is needed.
Group related options together so operations (e.g. valid, test, index total) can be performed on all options in the group.
Previously, options at the top of the hierarchy of the related options were used to do these tests. This was prone to error as option relationships changed and it was not always clear which option (or options) should be used.
Bug Fixes:
* Error with hints when backup user cannot read pg_settings. (Reviewed by Stefan Fercot, Cynthia Shang. Reported by Mohamed Insaf K.)
Features:
* PostgreSQL 13 support. (Reviewed by Cynthia Shang.)
Improvements:
* Improve PostgreSQL version identification. (Reviewed by Cynthia Shang, Stephen Frost.)
* Improve working directory error message. (Reviewed by Stefan Fercot.)
* Add hint about starting the stanza when WAL segment not found. (Contributed by David Christensen. Reviewed by David Steele.)
* Add hint for protocol version mismatch. (Reviewed by Cynthia Shang. Suggested by loop-evgeny.)
Documentation Improvements:
* Add note that pgBackRest versions must match when running remotely. (Reviewed by Cynthia Shang. Suggested by loop-evgeny.)
* Move info command text to the reference and link to user guide. (Reviewed by Cynthia Shang. Suggested by Christophe Courtois.)
* Update yum repository path for CentOS/RHEL user guide. (Contributed by Heath Lord. Reviewed by David Steele.)
This means the same text will appear in both places, which should make it easier to find.
Also update the link code to allow both page and section to be specified rather than only one or the other.
Update the documentation to explicitly state that versions must match across hosts when running remotely.
Add a hint to the protocol version mismatch error to help the user identify the problem.
Add older PostgreSQL versions to the u18 container that were not available before.
This also updates all minor versions for prior versions of PostgreSQL.
Scan the WAL archive for missing or invalid files and build up ranges of WAL that will be used to verify backup integrity. A number of errors and warnings are currently emitted but they should not be considered authoritative (yet).
The command is incomplete so is marked internal.
Previously, catalog versions were fixed for all versions which made maintaining the catalog versions during PostgreSQL beta and release candidate cycles very painful. A version of pgBackRest which was functionally compatible was rendered useless by a catalog version bump in PostgreSQL.
Instead use only the control version to identify a PostgreSQL version when possible. Some older versions require a catalog version to positively identify a PostgreSQL version, so include them when required.
Since the catalog number is required to work with tablespaces it will need to be stored. There's already a copy of it in backup.info so use that (even though we have been ignoring it in the C versions).
This condition used to give a not-very-clear error which we have been intending to improve. But in the meantime the changes in fbff299 resulted in a segfault for this condition instead because the data_directory was assumed to be non-NULL.
Fix this by explicitly throwing an error with hints when any row in pg_settings cannot be selected.
This file is created by pg_basebackup so might be in the data directory if the cluster was restored from a pg_basebackup backup. Also exclude backup_manifest.tmp since it is possible to find that in the backup directory.
Improve the wording of the error message and add a hint to make it clearer what is wrong and how the user can fix it.
Also change the assert to a regular error since this is not an internal error.
If a stop command has been issued the check command fails due to archiving timing out.
Provide a hint to document this situation and point the user in the proper direction.
If the callback never returned any jobs then protocolParallelDone() would never be true. The reason is that the done state was being set in protocolParallelResult(), which never gets called if there are no results.
Calling protocolParallelResult() doesn't make much sense in this case so instead move the done logic to protocolParallelDone().
For current usage of ProtocolParallel we ensure there are jobs before processing so this is not a live issue, but the new behavior is required for future development.
Bug Fixes:
* Suppress errors when closing local/remote processes. Since the command has completed it is counterproductive to throw an error but still warn to indicate that something unusual happened. (Reviewed by Cynthia Shang. Reported by argdenis.)
* Fix issue with = character in file or database names. (Reviewed by Bastian Wegge, Cynthia Shang. Reported by Brad Nicholson, Bastian Wegge.)
Features:
* Automatically retrieve temporary S3 credentials on AWS instances. (Contributed by David Steele, Stephen Frost. Reviewed by Cynthia Shang, David Youatt, Aleš Zelený, Jeanette Bromage.)
* Add archive-mode option to disable archiving on restore. (Reviewed by Stephen Frost. Suggested by Stephen Frost.)
Improvements:
* PostgreSQL 13 beta3 support. Changes to the control/catalog/WAL versions in subsequent betas may break compatibility but pgBackRest will be updated with each release to keep pace.
* Asynchronous list/remove for S3/Azure storage. (Reviewed by Cynthia Shang, Stephen Frost.)
* Improve memory usage of unlogged relation detection in manifest build. (Reviewed by Cynthia Shang, Stephen Frost, Brad Nicholson, Oscar. Suggested by Oscar, Brad Nicholson.)
* Proactively close file descriptors after forking async process. (Reviewed by Stephen Frost, Cynthia Shang.)
* Delay backup remote connection close until after archive check. (Contributed by Floris van Nee. Reviewed by David Steele.)
* Improve detailed error output. (Reviewed by Cynthia Shang.)
* Improve TLS error reporting. (Reviewed by Cynthia Shang, Stephen Frost.)
Documentation Bug Fixes:
* Add none to compress-type option reference and fix example. (Reported by Ugo Bellavance, Don Seiler.)
* Add missing azure type in repo-type option reference. (Fixed by Don Seiler. Reviewed by David Steele.)
* Fix typo in repo-cipher-type option reference. (Fixed by Don Seiler. Reviewed by David Steele.)
Documentation Improvements:
* Clarify that expire must be run regularly when expire-auto is disabled. (Reviewed by Douglas J Hunley. Suggested by Douglas J Hunley.)
When restoring a cluster that will be promoted but is not intended to be the new primary, it is important to disable archiving to avoid polluting the repository with useless WAL. This option makes disabling archiving a bit easier.
Automatically retrieve the role and temporary credentials for S3 when the AWS instance is associated with an IAM role. Credentials are automatically updated when they are <= 5 minutes from expiring.
Basic configuration is to set repo1-s3-key-type=auto. repo1-s3-role can be used to set a specific role, otherwise it will be retrieved automatically.
Add more info (command, version, options) to asserts, and errors when debug logging is enabled. This won't cover all cases but might mean we get more info in some circumstances.
Currently each module that needs to collect statistics implements custom code to do so. This is cumbersome.
Create a general purpose module for collecting and reporting statistics. Statistics are output in the log at detail level, but there are other uses they could be put to eventually.
No new functionality is added. This is just a drop-in replacement for the current statistics, with the advantage of being more flexible.
The new stats are slower because they involve a list lookup, but performance testing shows stats can be updated at about 40,000/ms which seems fast enough for our purposes.
Improve the performance of list/delete operations by using async requests.
It's questionable whether this will have any impact on Azure deletes since they are sent one at a time with little work done in between, but it doesn't hurt to try.
HTTP/1.0 connections are closed by default after a single response. Other than that, treat 1.0 the same as 1.1.
HTTP/1.0 allows different date formats that we can't parse but for now, at least, we don't need any date headers from 1.0 requests.
Following up on 111d33c, implement the new interfaces for socket client/session. Now HTTP objects can be used over TLS or plain sockets.
This required adding ioSessionFd() and ioSessionRole() to provide the functionality of sckSessionFd() and sckSessionType(). sckClientHost() and sckClientPort don't make sense in a generic interface so they were replaced with ioSessionName().
Only close the remote connection after verifying that the WAL files have been received. This is necessary if the archive_command on the PostgreSQL host is conditional, i.e. archiving only happens while a backup lock is held, to ensure all WAL segments are archived.
Move sckSessionReadyRead()/Write() into the IoRead/IoWrite interfaces. This is a more logical place for them and the alternative would be to add them to the IoSession interface, which does not seem like a good idea.
This is mostly a refactor, but a big change is the select() logic in fdRead.c has been replaced by ioReadReady(). This was duplicated code that was being used by our protocol but not TLS. Since we have not had any problems with requiring poll() in the field this seems like a good time to remove our dependence on select().
Also, IoFdWrite now requires a timeout so update where required, mostly in the tests.
These interfaces allow the HttpClient and HttpSession objects to work with protocols other than TLS, .e.g. plain sockets. This is necessary to allow standard HTTP -- right now only HTTPS is allowed, i.e. HTTP over TLS.
For now only TlsClient and TlsSession have been converted to the new interfaces. SocketClient and SocketSession will also need to be converted but first sckSessionReadyRead() and sckSessionReadyWrite() need to be moved into the IoRead and IoWrite interfaces, since they are not a good fit for IoSession.
Before 9f2d647 TLS errors included additional details in at least some cases. After 9f2d647 a connection to an HTTP server threw `TLS error [1]` instead of `unable to negotiate TLS connection: [336031996] unknown protocol`.
Bring back the detailed messages to make debugging TLS errors easier. Since the error routine is now generic the `unable to negotiate TLS connection context` is not available so the error looks like `TLS error [1:336031996] unknown protocol`.
PostgreSQL may be using most of the available file descriptors when it executes the the archive-get/archive-push commands (especially archive-get). This can lead to problems depending on how many file descriptors are needed for parallelism in the async process.
Proactively free file descriptors between 3 and 1023 to help ensure there are enough available for reasonable values of process-max, i.e. <= 300.
This loop was using a lot of memory without freeing it at intervals.
Rewrite to use char arrays when possible to reduce memory that needs to be allocated and freed.
The fix for = characters in info files (039d314) added JSON validation but discarded the resulting Variant which means the JSON is being parsed twice. This nearly doubles the time to load a manifest since a lot of complex JSON is involved.
Time to load a million file manifest:
Before 039d314: 7.8s
039d314: 15.5s
This patch: 7.5s
To fix this regression return the Variant in the callback so the caller does not have to parse it again. The new code appears slightly more efficient overall, probably because there are fewer operations against Strings.
The manifest uses the = character as the key/value separator so = characters in the key cause parsing errors and lead to an error or segfault.
Since the value must be valid JSON we can keep checking the value on the right side of the = and stop building the key when the value is valid. It's a bit hackish but it does seem to do the job without breaking the manifest format.
Unsurprisingly this makes parsing about 50% slower but it's still more than fast enough. Parsing 10 million key/values takes about 6.5s for the old code and 10s for the new code. Since the value is used as JSON downstream we can reclaim most of this time by just passing the JSON value rather than making the callback reparse it. We'll save that for another commit, though.
Since the command has completed it is counterproductive to throw an error but still warn to indicate that something unusual happened.
Also fix the related issue that the local processes were not being shut down when they completed, which meant that they might timeout before being closed when pgbackrest terminated.
Bug Fixes:
* Fix restore --force acting like --force --delta. This caused restore to replace files based on timestamp and size rather than overwriting, which meant some files that should have been updated were left unchanged. Normal restore and restore --delta were not affected by this issue. (Reviewed by Cynthia Shang.)
Features:
* Azure support for repository storage. (Reviewed by Cynthia Shang, Don Seiler.)
* Add expire-auto option. This allows automatic expiration after a successful backup to be disabled. (Contributed by Stefan Fercot. Reviewed by Cynthia Shang, David Steele.)
Improvements:
* Asynchronous S3 multipart upload. (Reviewed by Stephen Frost.)
* Automatic retry for backup, restore, archive-get, and archive-push. (Reviewed by Cynthia Shang.)
* Disable query parallelism in PostgreSQL sessions used for backup control. (Reviewed by Stefan Fercot.)
* PostgreSQL 13 beta2 support. Changes to the control/catalog/WAL versions in subsequent betas may break compatibility but pgBackRest will be updated with each release to keep pace.
* Improve handling of invalid HTTP response status. (Reviewed by Cynthia Shang.)
* Improve error when pg1-path option missing for archive-get command. (Reviewed by Cynthia Shang.)
* Add hint when checksum delta is enabled after a timeline switch. (Reviewed by Matt Bunter, Cynthia Shang.)
* Use PostgreSQL instead of postmaster where appropriate. (Reviewed by Cynthia Shang.)
Documentation Bug Fixes:
* Fix incorrect example for repo-retention-full-type option. (Reported by Höseyin Sönmez.)
* Remove internal commands from HTML and man command references. (Reported by Cynthia Shang.)
Documentation Improvements:
* Update PostgreSQL versions used to build user guides. Also add version ranges to indicate that a user guide is accurate for a range of PostgreSQL versions even if it was built for a specific version. (Reviewed by Stephen Frost.)
* Update FAQ for expiring a specific backup set. (Contributed by Cynthia Shang. Reviewed by David Steele.)
* Update FAQ to clarify default PITR behavior. (Contributed by Cynthia Shang. Reviewed by David Steele.)
Remove all check and stanza-* tests except for the ones that are intended to succeed. The successful tests show that the queries run with expected results against each version of PG which should also validate queries for the failure tests in the unit tests.
Also remove the tests for --no-online backups since they don't require a database and are well tested in the unit tests.
The prior code was only able to use the main passphrase automatically and expected sub passphrases to be specified for each operation. This was fine for testing but hardly sufficient for a user-facing feature.
Update the code to determine which passphrase to use for any file in the repository and error when an invalid file or location is selected.
The repo-get command is still internal for now, but with this improvement it should be ready to be made public.
If a local command, e.g. backupFile(), fails it will stop the entire process. Instead, retry local commands to deal with transient errors.
Remove special logic in the S3 storage driver to retry RequestTimeTooSkewed errors since this is now handled by the general retry mechanism in the places where it is most likely to happen, i.e. file read/write. Also, this error should have been entirely eliminated by the asynchronous TLS implementation.
A shared access signature (SAS) provides granular, delegated access to resources in a storage account. This is often preferable to using a shared key which provides more access and is a greater security risk if compromised.
This caused restore to replace files based on timestamp and size rather than overwriting, which meant some files that should have been updated were left unchanged. Normal restore and restore --delta were not affected by this issue.
Azure and Azure-compatible object stores can now be used for repository storage.
Currently only shared key authentication is supported but SAS will be added soon.
There don't appear to be any behavioral changes since PostgreSQL 12 and all the tests pass.
Changes to the control/catalog/WAL versions in subsequent betas may break compatibility but pgBackRest will be updated with each release to keep pace.
There is no need to have parallelism enabled in a backup control session. In particular, 9.6 marks pg_stop_backup() as parallel-safe but an error will be thrown if pg_stop_backup() is run in a worker.
When uploading large files the upload is split into multiple parts which are assembled at the end to create the final file. Previously we waited until each part was acknowledged before starting on the processing (i.e. compression, etc.) of the next part.
Now, the request for each part is sent while processing continues and the response is read just before sending the request for the next part. This asynchronous method allows us to continue processing while the S3 server formulates a response.
Testing from outside AWS in a high-bandwidth, low-latency environment showed a 35% improvement in the upload time of 1GB files. The time spent waiting for multipart notifications was reduced by ~300% (this measurement included the final part which is not uploaded asynchronously).
There are still some possible improvements: 1) the creation of the multipart id could be made asynchronous when it looks like the upload will need to be multipart (this may incur cost if the upload turns out not to be multipart). 2) allow more than one async request (this will use more memory).
A fair amount of refactoring was required to make the HTTP responses asynchronous. This may seem like overkill but having well-defined request, response, and session objects will also be advantageous for the upcoming HTTP server functionality.
Another advantage is that the lifecycle of an HttpSession is better defined. We only want to reuse sessions that complete the request/response cycle successfully, otherwise we consider the session to be in a bad state and would prefer to start clean with a new one. Previously, this required complex notifications to mark a session as "successfully done". Now, ownership of the session is passed to the request and then the response and only returned to the client after a successful response. If an error occurs anywhere along the way the session will be automatically closed by the object destructor when the request/response object is freed (depending on which one currently owns the session).
strPtr() is called more than any other function and during profiling (with or without optimization) it can end up using a disproportionate amount of the total runtime. Even though it is fast, the profiler has a minimum resolution for each function call so strPtr() will often end up towards the top of the list even though the real runtime is quite small.
Instead, inline strPtr() and indicate to gcc that it should be inlined even for non-optimized builds, since that's how profiles are usually generated.
To make strPtr() smaller require "this" to be non-NULL and add another function, strPtrNull(), to deal with the few cases where we need NULL handling.
As a bonus this makes the executable about 1% smaller even when compared to a prior optimized build which would inline some percentage of strPtr() calls.
This aligns better with general PostgreSQL usage and our own documentation (updated in 4bcef702).
Usage in the backup.manifest tests has not been updated since it might break the file format.
Expressions only worked at the first level of recursion because the expression was also being applied to paths so the path had to match the filter in order to recurse.
This is not considered a bug since it does not affect any existing code paths, but it is required for the general-purpose repo-ls command.
A truncated HTTP response status could lead to an an unfriendly error message, which would be retried, but could be confusing if the error was persistent and required debugging.
Improve the error handling overall to catch more error cases explicitly and respond better to edge cases.
Also update the terminology in comments to align with the RFC. Variable and function names were not changed because a refactor is intended for HTTP response and it doesn't seem worth the additional code churn.
Bug Fixes:
* Fix issue checking if file links are contained in path links. (Reviewed by Cynthia Shang. Reported by Christophe Cavallié.)
* Allow pg-path1 to be optional for synchronous archive-push. (Reviewed by Cynthia Shang. Reported by Jerome Peng.)
* The expire command now checks if a stop file is present. (Fixed by Cynthia Shang. Reviewed by David Steele.)
* Handle missing reason phrase in HTTP response. (Reviewed by Cynthia Shang. Reported by Tenuun.)
* Increase buffer size for lz4 compression flush. (Reviewed by Cynthia Shang. Reported by Eric Radman.)
* Ignore pg-host* and repo-host* options for the remote command. (Reviewed by Cynthia Shang. Reported by Pavel Suderevsky.)
* Fix possibly missing pg1-* options for the remote command. (Reviewed by Cynthia Shang. Reported by Andrew L'Ecuyer.)
Features:
* Time-based retention for full backups. The --repo-retention-full-type option allows retention of full backups based on a time period, specified in days. (Contributed by Cynthia Shang, Pierre Ducroquet. Reviewed by David Steele.)
* Ad hoc backup expiration. Allow the user to remove a specified backup regardless of retention settings. (Contributed by Cynthia Shang. Reviewed by David Steele.)
* Zstandard compression support. Note that setting compress-type=zst will make new backups and archive incompatible (unrestorable) with prior versions of pgBackRest. (Reviewed by Cynthia Shang.)
* bzip2 compression support. Note that setting compress-type=bz2 will make new backups and archive incompatible (unrestorable) with prior versions of pgBackRest. (Contributed by Stephen Frost. Reviewed by David Steele, Cynthia Shang.)
* Add backup/expire running status to the info command. (Contributed by Stefan Fercot. Reviewed by David Steele.)
Improvements:
* Expire WAL archive only when repo-retention-archive threshold is met. WAL prior to the first full backup was previously expired after the first full backup. Now it is preserved according to retention settings. (Contributed by Cynthia Shang. Reviewed by David Steele.)
* Add local MD5 implementation so S3 works when FIPS is enabled. (Reviewed by Cynthia Shang, Stephen Frost. Suggested by Brian Almeida, John Kelley.)
* PostgreSQL 13 beta1 support. Changes to the control/catalog/WAL versions in subsequent betas may break compatibility but pgBackRest will be updated with each release to keep pace. (Reviewed by Cynthia Shang.)
* Reduce buffer-size default to 1MiB. (Reviewed by Stephen Frost.)
* Throw user-friendly error if expire is not run on repository host. (Contributed by Cynthia Shang. Reviewed by David Steele.)
The purpose of the remote command is to get access to local resources, so a remote should never start another remote. However, this could happen if there were host settings on the remote host, which ended badly with lock errors, loops, etc.
Add pg-local and repo-local options to indicate that the resource is local even if there are host settings.
Note that for the time being these options are internal and not intended for general usage. However, this is likely the direction needed to allow for more symmetric and manageable configurations.
Some pg1-* options are required by the remote so if they are not provided in the remote's configuration file then it may cause a configuration error, depending on the operation. This currently only applies to the pg1-path option.
This is still an issue for repo-* options but the same solution cannot be applied because some repo-* options are secure and cannot be passed on the command-line.
There don't appear to be any behavioral changes since PostgreSQL 12 and all the tests pass.
Changes to the control/catalog/WAL versions in subsequent betas may break compatibility but pgBackRest will be updated with each release to keep pace.
S3 requires the Content-MD5 header for many requests but MD5 is not available via OpenSSL when FIPS is enabled because it is considered to be insecure.
Even though our usage does not present any security risks a local M5 implementation is required to circumvent the over-broad FIPS restriction.
Vendorize the MD5 implementation found at https://openwall.info/wiki/people/solar/software/public-domain-source-code/md5 and add full coverage for the module in the common/crypto unit tests.
The prior default was determined by benchmarking the Perl code prior to the 1.0 release. In general buffer allocation was more expensive in Perl so large buffers gave the best performance. This was due to multiple buffer allocations for each filter in an IO operation.
The C code allocates fixed buffers for each IO operation so the cost for buffer allocation is lower than Perl. That being the case it made sense to benchmark the C code to determine the optimal buffer default.
The performance/storage tests were used to measure the performance of a variety of filters. 1GiB of data was processed by each filter 10 times and the results of the tests were averaged.
While most buffer sizes gave similar performance, 1MiB appeared to perform the best overall. Of course, different architectures are likely to yield different results but this seems like a sensible default. The buffer-size option may still need to be manually configured to give optimal results.
Raw test data for reference:
4MB buffer (prior default)
copy time 1807ms, avg time 180ms, avg throughput: 5942MB/s
md5 time 14200ms, avg time 1420ms, avg throughput: 756MB/s
sha1 time 11431ms, avg time 1143ms, avg throughput: 939MB/s
sha256 time 23463ms, avg time 2346ms, avg throughput: 457MB/s
gzip -6 time 381199ms, avg time 38119ms, avg throughput: 28MB/s
lz4 -1 time 15484ms, avg time 1548ms, avg throughput: 693MB/s
1MB buffer (new default)
copy time 1760ms, avg time 176ms, avg throughput: 6100MB/s
md5 time 13739ms, avg time 1373ms, avg throughput: 781MB/s
sha1 time 11025ms, avg time 1102ms, avg throughput: 973MB/s
sha256 time 22539ms, avg time 2253ms, avg throughput: 476MB/s
gzip -6 time 372995ms, avg time 37299ms, avg throughput: 28MB/s
lz4 -1 time 15118ms, avg time 1511ms, avg throughput: 710MB/s
512K buffer
copy time 1782ms, avg time 178ms, avg throughput: 6025MB/s
md5 time 13724ms, avg time 1372ms, avg throughput: 782MB/s
sha1 time 10959ms, avg time 1095ms, avg throughput: 979MB/s
sha256 time 22982ms, avg time 2298ms, avg throughput: 467MB/s
gzip -6 time 378120ms, avg time 37812ms, avg throughput: 28MB/s
lz4 -1 time 15484ms, avg time 1548ms, avg throughput: 693MB/s
256K buffer
copy time 1805ms, avg time 180ms, avg throughput: 5948MB/s
md5 time 13706ms, avg time 1370ms, avg throughput: 783MB/s
sha1 time 11074ms, avg time 1107ms, avg throughput: 969MB/s
sha256 time 22588ms, avg time 2258ms, avg throughput: 475MB/s
gzip -6 time 372645ms, avg time 37264ms, avg throughput: 28MB/s
lz4 -1 time 16346ms, avg time 1634ms, avg throughput: 656MB/s
Reason phrases (e.g. OK) are optional in HTTP 1.1 but the space after the status code is not. When the reason phrase was missing the required space was trimmed along with the trailing CR leading to a format error.
Rework the logic to preserve the space and allow empty reason phrases.
Found while testing against the Backblaze S3-compatible API.
Some lz4 versions between r131 and 1.7.5 did not return a sufficient buffer size from LZ4F_compressBound() to allow LZ4F_compressEnd() to complete reliably. While this issue was fixed in lz4 1.7.5 there are affected versions in supported distributions such as CentOS/RHEL 7.
Use one of the hacks suggested in https://github.com/lz4/lz4/issues/290 to increase the buffer size enough for LZ4F_compressEnd() to complete. This means that a slightly larger buffer size is required for all versions but it seems worth it to (hopefully) to fix the issue in all lz4 versions.
Update error types throw by bzip2 to be more consistent with gzip.
Update the bzip2 and gzip error default to be AssertError as that's the more common case in both, and add a 'break;' to the default clause -- we don't intend to be just falling through those case statements, even if the default is the last, we should be explicit about that.
Clean up some tabs that snuck in, rename a variable to be more clear, and add some comments.
The --repo-retention-full-type option allows retention of full backups based on a time period, specified in days.
The new option will default to 'count' and therefore will not affect current installations. Setting repo-retention-full-type to 'time' will allow the user to use a time period, in days, to indicate full backup retention. Using this method, a full backup can be expired only if the time the backup completed is older than the number of days set with repo-retention-full (calculated from the moment the 'expire' command is run) and at least one full backup meets the retention period. If archive retention has not been configured, then the default settings will expire archives that are prior to the oldest retained full backup. For example, if there are three full backups ending in times that are 25 days old (F1), 20 days old (F2) and 10 days old (F3), then if the full retention period is 15 days, then only F1 will be expired; F2 will be retained because F1 is not at least 15 days old.
bzip2 is a widely available, high-quality data compressor. It typically compresses files to within 10% to 15% of the best available techniques (the PPM family of statistical compressors), while being around twice as fast at compression and six times faster at decompression.
bzip2 is currently available on all supported platforms.
Zstandard is a fast lossless compression algorithm targeting real-time compression scenarios at zlib-level and better compression ratios. It's backed by a very fast entropy stage, provided by Huff0 and FSE library.
Zstandard version >= 1.0 is required, which is generally only available on newer distributions.
If the WAL path is absolute then pg1-path should be optional but in fact it was required to load pg_control.
Skip the pg_control check when pg1-path is not specified. The check against the stanza version/system-id remains to protect the repo from corruption.
There is no conflict if the path containing a file link is a parent path of a path link. The Perl code apparently had this right but the migration to C missed it.
Exclude this case when checking for link conflicts.
There have been a number of segfaults reported because a string option expected to be non-null was actually null. This is generally due to options that are expected to be set but are in fact optional.
Protect against this by creating cfgOptionStrNull() to get options that can be null, while changing cfgOptionStr() to always expect non-null. There are relatively few places where nulls are expected.
There is definitely a chance for breakage here as null options might currently be working in the field but will be caught by this new check. Hopefully introducing the check early in the release cycle will allow us to catch any issues.
Previously when retention-archive was set (either by the user or by default), archives prior to the archive-start of the oldest remaining full backup (after backup expiration occurred) would be expired even though the retention-archive threshold had not been met. For example, if there were 1 full backup remaining after backup expiration and the retention-archive was set to 2 and retention-archive-type=full, then archives prior to the archive-start of the remaining full backup would still be removed even though retention-archive required 2 full backups remaining before archives should be expired.
The thought was to keep the archive directory clean and since the full backup did not require prior archives, it was safe to delete them. However, this has caused problems for some users in the past (because they needed the WAL for other purposes) and with the new adhoc and time-based retention features, it was decided that the archives should remain until the threshold was met. The archives will eventually be removed and if having them causes space issues, the expire command and the retention-archive can always be run and adjusted.
The specified backup set (i.e. the backup label provided and all of its dependent backups, if any) will be expired regardless of backup retention rules except that at least one full backup must remain in the repository.
This is implemented by checking for a backup lock on the host where info is running so there are a few limitations:
* It is not currently possible to know which command is running: backup, expire, or stanza-*. The stanza commands are very unlikely to be running so it's pretty safe to guess backup/expire. Command information may be added to the lock file to improve the accuracy of the reported command.
* If the info command is run on a host that is not participating in the backup, e.g. a standby, then there will be no backup lock. This seems like a minor limitation since running info on the repo or primary host is preferred.
Bug Fixes:
* Remove empty subexpression from manifest regular expression. MacOS was not happy about this though other platforms seemed to work fine. (Fixed by David Raftis.)
Improvements:
* Non-blocking TLS implementation. (Reviewed by Slava Moudry, Cynthia Shang, Stephen Frost.)
* Only limit backup copy size for WAL-logged files. The prior behavior could possibly lead to postgresql.conf or postgresql.auto.conf being truncated in the backup. (Reviewed by Cynthia Shang.)
* TCP keep-alive options are configurable. (Suggested by Marc Cousin.)
* Add io-timeout option.
Timeout used for connections and read/write operations.
Note that the entire read/write operation does not need to complete within this timeout but some progress must be made, even if it is only a single byte.
The prior blocking implementation seemed to be prone to locking up on some (especially recent) kernel versions. Since we were unable to reproduce the issue in a development environment we can only speculate as to the cause, but there is a good chance that blocking sockets were the issue or contributed to the issue.
So move to a non-blocking implementation to hopefully clear up these issues. Testing in production environments that were prone to locking shows that the approach is promising and at the very least not a regression.
The main differences from the blocking version are the non-blocking connect() implementation and handling of WANT_READ/WANT_WRITE retries for all SSL*() functions.
Timeouts in the tests needed to be increased because socket connect() and TLS SSL_connect() were not included in the timeout before. The tests don't run any slower, though. In fact, all platforms but Ubuntu 12.04 worked fine with the shorter timeouts.
select() is a bit old-fashioned and cumbersome to use. Since the select() code needed to be modified to handle write ready this seems like a good time to upgrade to poll().
poll() has been around for a long time so there doesn't seem to be any need to provide a fallback to select().
Also change the error on timeout from FileReadError to ProtocolError. This works better for read vs. write and failure to poll() is indicative of a protocol error or unexpected EOF.
The prior behavior introduced in dcddf3a5 could possibly lead to postgresql.conf or postgresql.auto.conf being truncated in the backup since they are copied via tmp files and could change size during the backup.
In general it seems safer to limit this feature to WAL-logged files which will be reconstructed during recovery.
A session looks much the same whether it is initiated from the client or the server, so use the session objects to implement the TLS, HTTP, and S3 test servers.
For TLS, at least, there are some differences between client and server sessions so add a client/server type to SocketSession to determine how the session was initiated.
Aside from reducing code duplication, the main advantage is that the test server will now timeout rather than hanging indefinitely when less input that expected is received.
Previously an error was only thrown when errno was set but in practice this is usually not the case. This may have something to do with getting errno late but attempts to get it earlier have not been successful. It appears that errno usually gets cleared and spot research seems to indicate that other users have similar issues.
An error at this point indicates unexpected EOF so it seems better to just throw an error all the time and be consistent.
To test this properly our test server needs to call SSL_shutdown() except when the client expects this error.
This abstraction allows the session code to be shared between the TLS client and (upcoming) server code.
Session management is no longer implemented in TlsClient so the HttpClient was updated to free and create sessions as needed. No test changes were required for HttpClient so the functionality should be unchanged.
Mechanical changes to the TLS tests were required to use TlsSession where appropriate rather than TlsClient. There should be no change in functionality other than how sessions are managed, i.e. using tlsClientOpen()/tlsSessionFree() rather than just tlsClientOpen().
The errorInternalThrowSys*() functions were marked as returning during coverage testing even when they had no possibility to return, i.e. the error parameter was set to constant true. This meant the compiler would treat the functions as returning even when they would not.
Instead create completely separate functions for coverage to use for THROW_ON_SYS_ERROR*() that can return and leave the regular functions marked __noreturn__.
This abstraction allows the session code to be shared between the socket client and (upcoming) server code. There should no difference in how the code works -- only the organization has changed. Note that no changes to the tests were required.
This same abstraction will be required for TlsClient but that will be done in a separate commit because it requires test changes.
The storage driver requires two list functions to be implemented, list and infoList. But the former is a subset of the latter so implementing both in every driver is wasteful. The reason both exist is that in Posix it is cheaper to get a list of names than it is to stat files to get size, time, etc. In S3 these operations are equivalent.
Introduce storageInfoLevelType to determine the amount of information required by the caller. That way Posix can work efficiently and all drivers can return only the data required which saves some bandwidth. The storageList() and storageInfoList() functions remain in the storage interface since they are useful -- the only change is simplifying the drivers with no external impact.
Note that since list() accepted an expression infoList() must now do so. Checking the expression is optional for the driver but can be used to limit results or save IO costs.
Similarly, exists() and pathExists() are just specialized forms of info() so adapt them to call info() instead.
Prior to 2.25 the individual TCP keep-alive options were not being configured due to a missing header. In 2.25 they were being configured incorrectly due to a disconnect between the timeout specified in ms and what was expected by the TCP options, i.e. seconds.
Instead make the TCP keep-alive options directly configurable, with correct units and better testing. Keep-alive is enabled by default (though it can be defaulted to the system setting instead) and the rest of the options are not set by default. This is in line with what PostgreSQL does, though PostgreSQL does not allow keep-alive to be defaulted.
Also move configuration of TCP options before connect() as PostgreSQL does.
Features:
* Add lz4 compression support. Note that setting compress-type=lz4 will make new backups and archive incompatible (unrestorable) with prior versions of pgBackRest. (Reviewed by Cynthia Shang.)
* Add --dry-run option to the expire command. Use dry-run to see which backups/archive would be removed by the expire command without actually removing anything. (Contributed by Cynthia Shang, Luca Ferrari.)
Improvements:
* Improve performance of remote manifest build. (Suggested by Jens Wilke.)
* Fix detection of keepalive options on Linux. (Contributed by Marc Cousin.)
* Add configure host detection to set standards flags correctly. (Contributed by Marc Cousin.)
* Remove compress/compress-level options from commands where unused. These commands (e.g. restore, archive-get) never used the compress options but allowed them to be passed on the command line. Now they will error when these options are passed on the command line. If these errors occur then remove the unused options. (Reviewed by Cynthia Shang.)
* Limit backup file copy size to size reported at backup start. If a file grows during the backup it will be reconstructed by WAL replay during recovery so there is no need to copy the additional data. (Reviewed by Cynthia Shang.)
Other storage*InfoList() functions do this but it was missed here.
memResize()/memFree() operations become more expensive as the mem context grows larger so freeing it periodically saves processing time.
If a file grows during the backup it will be reconstructed by WAL replay during recovery so there is no need to copy the additional data.
This also reduces the likelihood of seeing torn pages during the copy. Torn pages can still occur in the middle of the file, though, so they must be handled.
This code stanza was not being included on Linux platforms because of a missing header file.
Also update the order of operations and make the timeout calculations more sensible.
LZ4 compresses data faster than gzip but at a lower ratio. This can be a good tradeoff in certain scenarios.
Note that setting compress-type=lz4 will make new backups and archive incompatible (unrestorable) with prior versions of pgBackRest.
Add compress-type option and deprecate compress option. Since the compress option is boolean it won't work with multiple compression types. Add logic to cfgLoadUpdateOption() to update compress-type if it is not set directly. The compress option should no longer be referenced outside the cfgLoadUpdateOption() function.
Add common/compress/helper module to contain interface functions that work with multiple compression types. Code outside this module should no longer call specific compression drivers, though it may be OK to reference a specific compression type using the new interface (e.g., saving backup history files in gz format).
Unit tests only test compression using the gz format because other formats may not be available in all builds. It is the job of integration tests to exercise all compression types.
Additional compression types will be added in future commits.
These commands (e.g. restore, archive-get) never used the compress options but allowed them to be passed on the command line. Now they will error when these options are passed on the command line. If these errors occur then remove the unused options.
The prior code used TRY...CATCH blocks to cleanup mem contexts when an error occurred. This included freeing new mem contexts that were still being initialized when the error occurred and ensuring that the prior memory context was restored.
This worked fine in production but it involved a lot of setjmp()/longjmp() calls that resulted in longer compilation times and sluggish performance under valgrind, profiling, and coverage testing.
Instead maintain a stack of new contexts and context switches that can be used to do cleanup after an error. Normally, the stack is not used for this purpose and pushing/popping is a cheap operation. In the prior implementation most of the TRY...CATCH logic needed to be run even on success.
One bonus is that the binary is about 8% smaller after this change. Another benefit is that new contexts *must* be explicitly freed/discarded or an error will occur. See info/manifest.c for an example of where this is useful outside the standard macros.
Bug Fixes:
* Prevent defunct processes in asynchronous archive commands. (Reviewed by Stephen Frost. Reported by Adam Brusselback, ejberdecia.)
* Error when archive-get/archive-push/restore are not run on a PostgreSQL host. (Reviewed by Stephen Frost. Reported by Jesper St John.)
* Read HTTP content to eof when size/encoding not specified. (Reviewed by Cynthia Shang. Reported by Christian ROUX.)
* Fix resume when the resumable backup was created by Perl. In this case the resumable backup should be ignored, but the C code was not able to load the partial manifest written by Perl since the format differs slightly. Add validations to catch this case and continue gracefully. (Reported by Kacey Holston.)
Features:
* Auto-select backup set on restore when time target is specified. Auto-selection is performed only when --set is not specified. If a backup set for the given target time cannot not be found, the latest (default) backup set will be used. (Contributed by Cynthia Shang.)
Improvements:
* Skip pg_internal.init temp file during backup. (Reviewed by Cynthia Shang. Suggested by Michael Paquier.)
* Add more validations to the manifest on backup. (Reviewed by Cynthia Shang.)
Documentation Improvements:
* Prevent lock-bot from adding comments to locked issues. (Suggested by Christoph Berg.)
If PostgreSQL crashes it can leave behind a pg_internal.init temp file with the pid as the extension, as discussed in https://www.postgresql.org/message-id/flat/20200131045352.GB2631%40paquier.xyz#7700b9481ef5b0dd5f09cc410b4750f6. On restart this file is not cleaned up so it can persist for the lifetime of the cluster or until another process with the same id happens to write pg_internal.init.
This is arguably a bug in PostgreSQL, but in any case it makes sense not to backup this file.
This error was lost during the migration to C. The error that occurred instead (generally an SSH auth error) was hard to debug.
Restore the original behavior by throwing an error immediately if pg1-host is configured for any of these commands. reset-pg1-host can be used to suppress the error when required.
The main improvement is a double-fork to prevent zombie processes if the parent process exits after the (child) async process. This is a real possibility since the parent process sticks around to monitor the results of the async process.
In the first fork, ignore SIGCHLD in the very unlikely case that the async process exits before the first fork. This is probably only possible if the async process exits immediately, perhaps due to a chdir() failure. Set SIGCHLD back to default in the async process so waitpid() will work as expected.
Also update the comment on chdir() to more accurately reflect what is happening.
Finally, add a test in certain debug builds to ensure the first fork exits very quickly. This only works when valgrind is not in use because valgrind makes forking so slow that it is hard to tell if the async process performed work or not (in the case that the second fork goes missing and the async process is a direct child).
In this case the resumable backup should be ignored, but the C code was not able to load the partial manifest written by Perl since the format differs slightly. Add validations to catch this case and continue gracefully.
Generally, the content-size or content-encoding headers will be used to specify how much content should be expected.
There is a special case where the server sends 'Connection:close' without the content headers and the content may be read up until eof.
This appears to be an atypical usage but it is required by the specification.
Auto-selection is performed only when --set is not specified. If a backup set for the given target time cannot not be found, the latest (default) backup set will be used.
Currently a limited number of date formats are recognized and timezone names are not allowed, only timezone offsets.
Validate that checksums exist for zero size files. This means that the checksums for zero size files are explicitly set by backup even though they'll always be the same. Also validate that zero length files have the correct checksum.
Validate that repo size is > 0 if size is > 0. No matter what compression type is used a non-zero amount of data cannot be stored in zero bytes.
Bug Fixes:
* Fix missing files corrupting the manifest. If a file was removed by PostgreSQL during the backup (or was missing from the standby) then the next file might not be copied and updated in the manifest. If this happened then the backup would error when restored. (Reviewed by Cynthia Shang. Reported by Vitaliy Kukharik.)
Improvements:
* Use pkg-config instead of xml2-config for libxml2 build options. (Contributed by David Steele, Adrian Vondendriesch.)
* Validate checksums are set in the manifest on backup/restore. (Reviewed by Cynthia Shang.)
This is a modest start but it addresses the specific issue that was caused by the bug fixed in 45ec694a. This validation will produce an immediate error rather than erroring out partway through the restore.
More validations are planned but this is the most important one and seems safest for this release.
If a file was removed by PostgreSQL during the backup (or was missing from the standby) then the next file might not be copied and updated in the manifest. If this happened then the backup would error when restored.
The issue was that removing files from the manifest invalidated the pointers stored in the processing queues. When a file was removed, all the pointers shifted to the next file in the list, causing a file to be unprocessed. Since the unprocessed file was still in the manifest it would be saved with no checksum, causing a failure on restore.
When process-max was > 1 then the bug would often not express since the file had already been pulled from the queue and updates to the manifest are done by name rather than by pointer.
pkg-config is a generic way to get build options rather than relying on a package-specific utility.
XML2_CONFIG can be used to override this utility for systems that do not ship pkg-config.
Bug Fixes:
* Fix error in timeline conversion. The timeline is required to verify WAL segments in the archive after a backup. The conversion was performed base 10 instead of 16, which led to errors when the timeline was ≥ 0xA. (Reported by Lukas Ertl, Eric Veldhuyzen.)
The timeline is required to verify WAL segments in the archive after a backup. The conversion was performed base 10 instead of 16, which led to errors when the timeline was ≥ 0xA.
Bug Fixes:
* Fix options being ignored by asynchronous commands. The asynchronous archive-get/archive-push processes were not loading options configured in command configuration sections, e.g. [global:archive-get]. (Reviewed by Cynthia Shang. Reported by Urs Kramer.)
* Fix handling of \ in filenames. \ was not being properly escaped when calculating the manifest checksum which prevented the manifest from loading. Since instances of \ in cluster filenames should be rare to nonexistent this does not seem likely to be a serious problem in the field.
Features:
* pgBackRest is now pure C.
* Add pg-user option. Specifies the database user name when connecting to PostgreSQL. If not specified pgBackRest will connect with the local OS user or PGUSER, which was the previous behavior. (Contributed by Mike Palmiotto.)
* Allow path-style URIs in S3 driver.
Improvements:
* The backup command is implemented entirely in C. (Reviewed by Cynthia Shang.)
The local, remote, archive-get-async, and archive-push-async commands were used to run functionality that was not directly available to the user. Unfortunately that meant they would not pick up options from the command that the user expected, e.g. backup, archive-get, etc.
Remove the internal commands and add roles which allow pgBackRest to determine what functionality is required without implementing special commands. This way the options are loaded from the expected command section.
Since remote is no longer a specific command with its own options, more manipulation is required when calling remote. This might be something we can improve in the config system but it may be worth leaving as is because it is a one-off, for now at least.
Although path-style URIs have been deprecated by AWS, they may still be used with products like Minio because no additional DNS configuration is required.
Path-style URIs must be explicitly enabled since it is not clear how they can be auto-detected reliably. More importantly, faulty detection could cause regressions in current installations.
Previously dates were not being filled by these functions which was fine since dates were not used.
We plan to use dates for the ls command plus it makes sense for the driver to be complete since it will be used as an example.
These are similar to what mktime() and strptime() do but they ignore the local system timezone which saves having to munge the TZ env variable to do time conversions.
Specifies the database user name when connecting to PostgreSQL.
If not specified pgBackRest will connect with the local OS user or PGUSER, which was the previous behavior.
\ was not being properly escaped when calculating the manifest checksum which prevented the manifest from loading.
Use jsonFromStr() to properly quote and escape \.
Since instances of \ in cluster filenames should be rare to nonexistent this does not seem likely to be a serious problem in the field.
Remove embedded Perl from the distributed binary. This includes code, configure, Makefile, and packages. The distributed binary is now pure C.
Remove storagePathEnforceSet() from the C Storage object which allowed Perl to write outside of the storage base directory. Update mock/all and real/all integration tests to use storageLocal() where they were violating this rule.
Remove "c" option that allowed the remote to tell if it was being called from C or Perl.
Code to convert options to JSON for passing to Perl (perl/config.c) has been moved to LibC since it is still required for Perl integration tests.
Update build and installation instructions in the user guide.
Remove all Perl unit tests.
Remove obsolete Perl code. In particular this included all the Perl protocol code which required modifications to the Perl storage, manifest, and db objects that are still required for integration testing but only run locally. Any remaining Perl code is required for testing, documentation, or code generation.
Rename perlReq to binReq in define.yaml to indicate that the binary is required for a test. This had been the actual meaning for quite some time but the key was never renamed.
For the most part this is a direct migration of the Perl code into C except as noted below.
A backup can now be initiated from a linked directory. The link will not be stored in the manifest or recreated on restore. If a link or directory does not already exist in the restore location then a directory will be created.
The logic for creating backup labels has been improved and it should no longer be possible to get a backup label earlier than the latest backup even with timezone changes or clock skew. This has never been an issue in the field that we know of, but we found it in testing.
For online backups all times are fetched from the PostgreSQL primary host (before only copy start was). This doesn't affect backup integrity but it does prevent clock skew between hosts affecting backup duration reporting.
Archive copy now works as expected when the archive and backup have different compression settings, i.e. when one is compressed and the other is not. This was a long-standing bug in the Perl code.
Resume will now work even if hardlink settings have been changed.
Reviewed by Cynthia Shang.
Bug Fixes:
* Fix archive-push/archive-get when PGDATA is symlinked. These commands tried to use cwd() as PGDATA but this would disagree with the path configured in pgBackRest if PGDATA was symlinked. If cwd() does not match the pgBackRest path then chdir() to the path and make sure the next cwd() matches the result from the first call. (Reported by Stephen Frost, Milosz Suchy.)
* Fix reference list when backup.info is reconstructed in expire command. Since the backup command is still using the Perl version of reconstruct this issue will not express unless 1) there is a backup missing from backup.info and 2) the expire command is run directly instead of running after backup as usual. This unlikely combination of events means this is probably not a problem in the field.
* Fix segfault on unexpected EOF in gzip decompression. (Reported by Stephen Frost.)
Commit 7168e074 tried to use cwd() as PGDATA but this would disagree with the path configured in pgBackRest if PGDATA was symlinked.
If cwd() does not match the pgBackRest path then chdir() to the path and make sure the next cwd() matches the result from the first call.
If the compressed stream terminated early then the decompression process would get a flush request (NULL input buffer) since the filter was not marked as done. This could happen on a zero-length or truncated (i.e. invalid) compressed file.
Change the existing assertion to an error to catch this condition in production gracefully.
Adding a manifest to backup.info was migrated to C in 4e4d1f41 but deduplication of the references was missed leading to a reference for every file being added to backup.info.
Since the backup command is still using the Perl version of reconstruct this issue will not express unless 1) there is a backup missing from backup.info and 2) the expire command is run directly instead of running after backup as usual.
This unlikely combination of events means this is probably not a problem in the field.
Bug Fixes:
* Fix remote timeout in delta restore. When performing a delta restore on a largely unchanged cluster the remote could timeout if no files were fetched from the repository within protocol-timeout. Add keep-alives to prevent remote timeout. (Reported by James Sewell, Jens Wilke.)
* Fix handling of repeated HTTP headers. When HTTP headers are repeated they should be considered equivalent to a single comma-separated header rather than generating an error, which was the prior behavior. (Reported by donicrosby.)
Improvements:
* JSON output from the info command is no longer pretty-printed. Monitoring systems can more easily ingest the JSON without linefeeds. External tools such as jq can be used to pretty-print if desired. (Contributed by Cynthia Shang.)
* The check command is implemented entirely in C. (Contributed by Cynthia Shang.)
Documentation Improvements:
* Document how to contribute to pgBackRest. (Contributed by Cynthia Shang.)
* Document maximum version for auto-stop option. (Contributed by Brad Nicholson.)
Test Suite Improvements:
* Fix container test path being used when --vm=none. (Suggested by Stephen Frost.)
* Fix mismatched timezone in expect test. (Suggested by Stephen Frost.)
* Don't autogenerate embedded libc code by default. (Suggested by Stephen Frost.)
When HTTP headers are repeated they should be considered equivalent to a single comma-separated header rather than generating an error, which was the prior behavior.
Reported by donicrosby.
This is only needed when new code is added to the Perl C library, which is becoming rare as the migration progresses.
Also, the code will vary slightly based on the Perl version used for generation so for normal users it is just noise.
Suggested by Stephen Frost.
When performing a delta restore on a largely unchanged cluster the remote could timeout if no files were fetched from the repository within protocol-timeout.
Add keep-alives to prevent remote timeout.
Reported by James Sewell, Jens Wilke.
Note that building the manifest on each host has been temporarily removed.
This feature will likely be brought back as a non-default option (after the manifest code has been fully migrated to C) since it can be fairly expensive.
Features:
* PostgreSQL 12 support.
* Add info command set option for detailed text output. The additional details include databases that can be used for selective restore and a list of tablespaces and symlinks with their default destinations. (Contributed by Cynthia Shang. Suggested by Stephen Frost, ejberdecia.)
* Add standby restore type. This restore type automatically adds standby_mode=on to recovery.conf for PostgreSQL < 12 and creates standby.signal for PostgreSQL ≥ 12, creating a common interface between PostgreSQL versions. (Reviewed by Cynthia Shang.)
Improvements:
* The restore command is implemented entirely in C. (Reviewed by Cynthia Shang.)
Documentation Improvements:
* Document the relationship between db-timeout and protocol-timeout. (Contributed by Cynthia Shang. Suggested by James Chanco Jr.)
* Add documentation clarifications regarding standby repositories. (Contributed by Cynthia Shang.)
* Add FAQ for time-based Point-in-Time Recovery. (Contributed by Cynthia Shang.)
Recovery settings are now written into postgresql.auto.conf instead of recovery.conf. Existing recovery_target* settings will be commented out to help avoid conflicts.
A comment is added before recovery settings to identify them as written by pgBackRest since it is unclear how, in general, old settings will be removed.
recovery.signal and standby.signal are automatically created based on the recovery settings.
The additional details include databases that can be used for selective restore and a list of tablespaces and symlinks with their default destinations.
This information is not included in the JSON output because it requires reading the manifest which is too IO intensive to do for all manifests. We plan to include this information for JSON in a future release.
This restore type automatically adds standby_mode=on to recovery.conf.
This could be accomplished previously by setting --recovery-option=standby_mode=on but PostgreSQL 12 requires standby mode to be enabled by a special file named standby.signal.
The new restore type allows us to maintain a common interface between PostgreSQL versions.
For the most part this is a direct migration of the Perl code into C.
There is one important behavioral change with regard to how file permissions are handled. The Perl code tried to set ownership as it was in the manifest even when running as an unprivileged user. This usually just led to errors and frustration.
The C code works like this:
If a restore is run as a non-root user (the typical scenario) then all files restored will belong to the user/group executing pgBackRest. If existing files are not owned by the executing user/group then an error will result if the ownership cannot be updated to the executing user/group. In that case the file ownership will need to be updated by a privileged user before the restore can be retried.
If a restore is run as the root user then pgBackRest will attempt to recreate the ownership recorded in the manifest when the backup was made. Only user/group names are stored in the manifest so the same names must exist on the restore host for this to work. If the user/group name cannot be found locally then the user/group of the PostgreSQL data directory will be used and finally root if the data directory user/group cannot be mapped to a name.
Reviewed by Cynthia Shang.
The backup manifest stores a complete list of all files, links, and paths in a backup along with metadata such as checksums, sizes,
timestamps, etc. A list of databases is also included for selective restore.
The purpose of the manifest is to allow the restore command to confidently reconstruct the PostgreSQL data directory and ensure that
nothing is missing or corrupt. It is also useful for reporting, e.g. size of backup, backup time, etc.
For now, migrate enough functionality to implement the restore command.
Reviewed by Cynthia Shang.
Info files required three copies in memory to be loaded (the original string, an ini representation, and the final info object). Not only was this memory inefficient but the Ini object does sequential scans when searching for keys making large files very slow to load.
This has not been an issue since archive.info and backup.info are very small, but it becomes a big deal when loading manifests with hundreds of thousands of files.
Instead of holding copies of the data in memory, use a callback to deliver the ini data directly to the object when loading. Use a similar method for save to avoid having an intermediate copy. Save is a bit complex because sections/keys must be written in alpha order or older versions of pgBackRest will not calculate the correct checksum.
Also move the load retry logic to helper functions rather than embedding it in the Info object. This allows for more flexibility in loading and ensures that stack traces will be available when developing unit tests.
Reviewed by Cynthia Shang.
Bug Fixes:
* Improve slow manifest build for very large quantities of tables/segments. (Reported by Jens Wilke.)
* Fix exclusions for special files. (Reported by CluelessTechnologist, Janis Puris, Rachid Broum.)
Improvements:
* The stanza-create/update/delete commands are implemented entirely in C. (Contributed by Cynthia Shang.)
* The start/stop commands are implemented entirely in C. (Contributed by Cynthia Shang.)
* Create log directories/files with 0750/0640 mode. (Suggested by Damiano Albani.)
Documentation Bug Fixes:
* Fix yum.p.o package being installed when custom package specified. (Reported by Joe Ayers, John Harvey.)
Documentation Improvements:
* Build pgBackRest as an unprivileged user. (Suggested by Laurenz Albe.)
The {[os-type-is-centos]} expression was missing parens which meant "and" expressions built on it would always evaluate true if the os-type was centos6.
Reported by Joe Ayers, John Harvey.
Prior to 2.16 the Perl manifest code would skip any file that began with a dot. This was not intentional but it allowed PostgreSQL socket files to be located in the data directory. The new C code in 2.16 did not have this unintentional exclusion so socket files in the data directory caused errors.
Worse, the file type error was being thrown before the exclusion check so there was really no way around the issue except to move the socket files out of the data directory.
Special file types (e.g. socket, pipe) will now be automatically skipped and a warning logged to notify the user of the exclusion. The warning can be suppressed with an explicit --exclude.
Reported by CluelessTechnologist, Janis Puris, Rachid Broum.
Putting the checksum at the beginning of the file made it impossible to stream the file out when saving. The entire file had to be held in memory while it was checksummed so the checksum could be written at the beginning.
Instead place the checksum at the end. This does not break the existing Perl or C code since the read is not order dependent.
There are no plans to improve the Perl code to take advantage of this change, but it will make the C implementation more efficient.
Reviewed by Cynthia Shang.
pgBackRest was being built by root in the documentation which is definitely not best practice.
Instead build as the unprivileged default container user. Sudo privileges are still required to install.
Suggested by Laurenz Albe.
storagePosixInfoList() processed each directory in a single memory context. If the directory contained hundreds of thousands of files processing became very slow due to the number of allocations.
Instead, reset the memory context every thousand files to minimize the number of allocations active at once, improving both speed and memory consumption.
Reported by Jens Wilke.
The log directories/files were being created with a mix of modes depending on whether they were created in C or Perl. In particular, the C code was creating log files with the execute bit set for the user and group which was just odd.
Standardize on 750/640 for both code paths.
Suggested by Damiano Albani.
The Perl versions remain because they are still being used by the Perl stanza commands. Once the stanza commands are migrated they can be removed.
Contributed by Cynthia Shang.
Bug Fixes:
* Retry S3 RequestTimeTooSkewed errors instead of immediately terminating. (Reported by sean0101n, Tim Garton, Jesper St John, Aleš Zelený.)
* Fix incorrect handling of transfer-encoding response to HEAD request. (Reported by Pavel Suderevsky.)
* Fix scoping violations exposed by optimizations in gcc 9. (Reported by Christian Lange, Ned T. Crigler.)
Features:
* Add repo-s3-port option for setting a non-standard S3 service port.
Improvements:
* The local command for backup is implemented entirely in C. (Contributed by David Steele, Cynthia Shang.)
* The check command is implemented partly in C. (Reviewed by Cynthia Shang.)
Implement switch WAL and archive check in C but leave the rest in Perl for now.
The main idea was to have some real integration tests for the new database code so the rest of the migration can wait.
Reviewed by Cynthia Shang.
Migrate functionality from the Perl Db module to C. For now this is just enough to implement the WAL switch check.
Add the dbGet() helper function to get Db objects easily.
Create macros in harnessPq to make writing pq scripts easier by grouping commonly used functions together.
Reviewed by Cynthia Shang.
The cause of this error seems to be that a failed request takes so long that a subsequent retry at the http level uses outdated headers.
We're not sure if pgBackRest it to blame here (in one case a kernel downgrade fixed it, in another case an incorrect network driver was the problem) so add retries to hopefully deal with the issue if it is not too persistent. If SSL_write() has long delays before reporting an error then this will obviously affect backup performance.
Reported by sean0101n, Tim Garton, Jesper St John, Aleš Zelený.
If this option is set then ports appended to repo-s3-endpoint or repo-s3-host will be ignored.
Setting this option explicitly may be the only way to use a bare ipv6 address with S3 (since multiple colons confuse the parser) but we plan to improve this in the future.
This direct interface to libpq allows simple queries to be run against PostgreSQL and supports timeouts.
Testing is performed using a shim that can use scripted responses to test all aspects of the client code. The shim will be very useful for testing backup scenarios on complex topologies.
Reviewed by Cynthia Shang.
The local process is now entirely migrated to C. Since all major I/O operations are performed in the local process, the vast majority of I/O is now performed in C.
Contributed by David Steele, Cynthia Shang.
The HTTP server can use either content-length or transfer-encoding to indicate that there is content in the response. HEAD requests do not include content but return all the same headers as GET. In the HEAD case we were ignoring content-length but not transfer-encoding which led to unexpected eof errors on AWS S3. Our test server, minio, uses content-length so this was not caught in integration testing.
Ignore all content for HEAD requests (no matter how it is reported) and add a unit test for transfer-encoding to prevent a regression.
Found by Pavel Suderevsky.
gcc < 9 makes all compound literals function scope, even though the C spec requires them to be invalid outside the current scope. Since the compiler and valgrind were not enforcing this we had a few violations which caused problems in gcc >= 9.
Even though we are not quite ready to support gcc 9 officially, fix the scoping violations that currently exist in the codebase.
Reported by chrlange, Ned T. Crigler.
Maintaining the storage layer/drivers in two languages is burdensome. Since the integration tests require the Perl storage layer/drivers we'll need them even after the core code is migrated to C. Create an interface layer so the Perl code can be removed and new storage drivers/features introduced without adding Perl equivalents.
The goal is to move the integration tests to C so this interface will eventually be removed. That being the case, the interface was designed for maximum compatibility to ease the transition. The result looks a bit hacky but we'll improve it as needed until it can be retired.
Bug Fixes:
* Fix archive retention expiring too aggressively. (Fixed by Cynthia Shang. Reported by Mohamad El-Rifai.)
Improvements:
* The expire command is implemented entirely in C. (Contributed by Cynthia Shang.)
* The local command for restore is implemented entirely in C.
* Remove hard-coded PostgreSQL user so $PGUSER works. (Suggested by Julian Zhang, Janis Puris.)
* Honor configure --prefix option. (Suggested by Daniel Westermann.)
* Rename repo-s3-verify-ssl option to repo-s3-verify-tls. The new name is preferred because pgBackRest does not support any SSL protocol versions (they are all considered to be insecure). The old name will continue to be accepted.
Documentation Improvements:
* Add FAQ to the documentation. (Contributed by Cynthia Shang.)
* Use wal_level=replica in the documentation for PostgreSQL ≥ 9.6. (Suggested by Patrick McLaughlin.)
The problem expressed when repo1-archive-retention-type was set to diff. In this case repo1-archive-retention ended up being effectively equal to one, which meant PITR recovery was only possible from the last backup. WAL required for consistency was still preserved for all backups.
This issue is not present in the C migration committed at 434cd832, which was written before this bug was reported. Even so, we wanted to note this issue in the release notes in case any other users have been affected.
Fixed by Cynthia Shang.
Reported by Mohamad El-Rifai.
This implementation duplicates the functionality of the Perl code but does so with different logic and includes full unit tests.
Along the way at least one bug was fixed, see issue #748.
Contributed by Cynthia Shang.
The PostgreSQL user was hard-coded to the OS user which libpq will automatically use if $PGUSER is not set, so this code was redundant and prevented $PGUSER from working when set.
Suggested by Julian Zhang, Janis Puris.
These names more accurately reflect what the functions do and follow the convention started in Info and InfoPg.
Also remove the ignoreMissing parameter since it was never used.
Contributed by Cynthia Shang.
The documentation was using wal_level=hot_standby which is a deprecated setting.
Also remove the reference to wal_level=archive since it is no longer supported and is not recommended for older versions.
Suggested by Patrick McLaughlin.
The release notes are generally a direct reflection of the git log. So, ease the burden of maintaining the release notes by using the git log to determine what needs to be added.
Currently only non-dev items are required to be matched to a git commit but the goal is to account for all commits.
The git history cache is generated from the git log but can be modified to correct typos and match the release notes as they evolve. The commit hash is used to identify commits that have already been added to the cache.
There's plenty more to do here. For instance, links to the commits for each release item should be added to the release notes.
The first paragraph should match the first line of the commit message as closely as possible. The following paragraphs add more information.
Release items have been updated back to 2.01.
The new name is preferred because pgBackRest does not support any SSL protocol versions (they are all considered to be insecure).
The old name will continue to be accepted.
This is just the part of restore run by the local helper processes, not the entire command.
Even so, various optimizations in the code (like pipelining and optimizations for zero-length files) should make the restore command faster on object stores.
Bug Fixes:
* Fix segfault when process-max > 8 for archive-push/archive-get. (Reported by Jens Wilke.)
Improvements:
* Bypass database checks when stanza-delete issued with force. (Contributed by Cynthia Shang. Suggested by hatifnatt.)
* Add configure script for improved multi-platform support.
Documentation Features:
* Add user guides for CentOS/RHEL 6/7.
It would be better if the documentation could be generated on multiple operating systems all in one go, but the doc system currently does not allow vars to be changed once they are set.
The solution is to run the docs for each required OS and stitch the documentation together. It's not pretty but it works and the automation in release.pl should at least make it easy to use.
The url for the menu item referring to the index (i.e. site root page) should use {[project-url-root]}.
This allows the url to be set to different values depending on the location of the index.
This report replaces the lcov report that was generated manually for each release.
The lcov report was overly verbose just to say that we have virtually 100% coverage.
There are currently no options with multiple alternate (deprecated) names so the code to render them in the help command could not be covered.
Remove the uncovered code and add an error when multiple alternate names are configured. It's not clear that the current code was handling this correctly, so it will need to be reviewed if it comes up again.
Pre-calculate the value used by logAny() to improve performance and make it more likely to be inlined.
Move IF_LOG_ANY() into LOG_INTERNAL() to simplify the macros and improve performance of LOG() and LOG_PID(). If the message has no chance of being logged there's no reason to call logInternal().
Rename logWill() to logAny() because it seems more intuitive.
The branch coverage exclusion rules were overly broad and included functions that ended in a capital letter, which disabled all coverage for the statement. Improve matching so that all characters in the name must be upper-case for a match.
Some macros with internal branches accepted parameters that might contain conditionals. This made it impossible to tell which branches belonged to which, and in any case an overzealous exclusion rule was ignoring all branches in such cases. Add the DEBUG_COVERAGE flag to build a modified version of the macros without any internal branches to be used for coverage testing. In most cases, the branches were optimizations (like checking logWill()) that improve production performance but are not needed for testing. In other cases, a parameter needed to be added to the underlying function to handle the branch during coverage testing.
Also tweak the coverage rules so that macros without conditionals are automatically excluded from branch coverage as long as they are not themselves a parameter.
Finally, update tests and code where missing coverage was exposed by these changes. Some code was updated to remove existing coverage exclusions when it was a simple change.
Call stackTraceTestStop()/stackTraceTestStart() once per block instead of with every param call. This was done to be cautious but is not necessary and slows down development.
These functions were never built into production so had no impact there.
Filters had different ideas about what "done" meant and this added complication to the group filter processing. For example, gzip decompression would detect end of stream and mark the filter as done before it had been flushed.
Improve the IoFilter interface to give a consistent definition of done across all filters, i.e. no filter can be done until it has started flushing no matter what the underlying driver reports. This removes quite a bit of tricky logic in the processing loop which tried to determine when a filter was "really" done.
Also improve management of the input buffers by pointing directly to the prior output buffer (or the caller's input) to eliminate loops that set/cleared these buffers.
If content was zero-length then the IO object was not created. This put the burden on the caller to test that the IO object existed before checking eof.
Instead, create an IO object even if it will immediately return eof. This has little cost and makes the calling code simpler.
Also add an explicit test for zero-length files in S3 and a few assertions.
The rules for when a C remote is required are getting complicated and will get worse when restoreFile() is migrated.
Instead, set the --c option when a C remote is required. This option will be removed when the remote is entirely implemented in C.
Most of the *Free() functions are pretty generic so add macros to make creating them as easy as possible.
Create a distinction between *Free() functions that the caller uses to free memory and callbacks that free third-party resources. There are a number of cases where a driver needs to free resources but does not need a normal *Free() because it is handled by the interface.
Add common/object.h for macros that make object maintenance easier. This pattern can also be used for many more object functions.
Rename memContextCallback() to memContextCallbackSet() to be more consistent with other parts of the code.
Free all context memory when an exception is thrown from a callback. Previously only the child contexts would be freed and this resulted in some allocations being lost. In practice this is probably not a big deal since the process will likely terminate shortly, but there may well be cases where that is not true.
Add GLUE() macro which is useful for creating identifiers.
Move MACRO_TO_STR() here and rename it STRINGIFY(). This appears to be the standard name for this type of macro and it is also an awesome name.
Remove "File" and "Driver" from object names so they are shorter and easier to keep consistent.
Also remove the "driver" directory so storage implementations are visible directly under "storage".
The function pointer casting used when creating drivers made changing interfaces difficult and led to slightly divergent driver implementations. Unit testing caught production-level errors but there were a lot of small issues and the process was harder than it should have been.
Use void pointers instead so that no casts are required. Introduce the THIS_VOID and THIS() macros to make dealing with void pointers a little safer.
Since we don't want to expose void pointers in header files, driver functions have been removed from the headers and the various driver objects return their interface type. This cuts down on accessor methods and the vast majority of those functions were not being used. Move functions that are still required to .intern.h.
Remove the special "C" crypto functions that were used in libc and instead use the standard interface.
Add bufDup() and bufNewUsedC().
Arrange bufNewC() params to match bufNewUsedC() since they have always seemed backward.
Fix bufHex() to only render the used portion of the buffer and fix some places where used was not being set correctly.
Use a union to make macro assignments for all legal values without casting. This is much more likely to catch bad assignments.
There is only one instance in the core code where this helps. It is mostly helpful in the tests.
There is an argument to be made that only THROW_SYS_ERROR*() variants should be used in the core code to improve test coverage. If so, that will be the subject of a future commit.
Some functions (e.g. getpwnam()/getgrnam()) will return an error but not set errno. In this case there's no use in appending strerror(), which will be "Success". This is confusing since an error has just been reported.
At least in the examples above, an error with no errno set just means "missing" and our current error message already conveys that.
The remote list was at most 9 (based on pg[1-8]-* max index) so anything over 8 wrote into unallocated memory.
The remote for the main process is (currently) stored in position zero so do the same for remotes started from locals, since there should only be one. The main process will need to start more remotes in the future which is why there is extra space.
Reported by Jens Wilke.
Use autoconf to provide a basic configure script. WITH_BACKTRACE is yet to be migrated to configure and the unit tests still use a custom Makefile.
Each C file must include "build.auto.conf" before all other includes and defines. This is enforced by test.pl for includes, but it won't detect incorrect define ordering.
Update packages to call configure and use standard flags to pass options.
Update RHEL repos that have changed upstream. Remove PostgreSQL 9.3 since the RHEL6/7 packages have disappeared.
Remove PostgreSQL versions from U12 that are still getting minor updates so the container does not need to be rebuilt.
LZ4 is included for future development, but this seems like a good time to add it to the containers.
The function provides all the file/path/link information required to build a backup manifest.
Also update storageInfo() to provide the same information for a single file.
At the same time change the way that load constructors work (and are named) so that Ini objects do not persist after the constructors complete.
infoArchiveSave() is excluded from this commit since it is just a trivial call to infoPgSave() and won't be required soon.
In most cases the JSON type is known so this is more efficient than converting to Variant first, both in terms of memory and time.
Also rename some of the existing functions for consistency.
Variants were being used to expose String and StringList types but this can be done more simply with an additional method.
Using only strings also allows for a more efficient implementation down the road.
This greatly reduces calls to filter processing, which is a performance benefit, but also makes the trace logs smaller and easier to read.
However, this means that ioWriteFlush() will no longer work with filters since a full flush of IoFilterGroup would require an expensive reset. Currently ioWriteFlush() is not used in this scenario so for now just add an assert to ensure it stays that way.
These are more efficient than creating buffers in place when needed.
After replacement discovered that bufNewStr() and BufNewZ() were not being used in the core code so removed them. This required using the macros in tests which is not the usual pattern.
Since the introduction of blocking read drivers (e.g. IoHandleRead, TlsClient) the non-blocking drivers have used the same rules for determining maximum buffer size, i.e. read only as much as requested. This is necessary so the blocking drivers don't get stuck waiting for data that might not be coming.
Instead mark blocking drivers so IoRead knows how much buffer to allow for the read. The non-blocking drivers can now request the maximum number of bytes allowed by buffer-size.
