If backup_label is removed from a restored backup then PostgreSQL will instead use checkpoint information from pg_control to attempt (what is thinks is) crash recovery. This will nearly always result in a corrupt cluster because the checkpoint will not be from the beginning of the backup, and even if it is, the end point will not be specified, which could lead to recovery stopping too early.
To prevent this, invalidate the checkpoint LSN in pg_control on restore. If backup_label is removed then recovery will still fail because PostgreSQL will not be able to find the invalid checkpoint. The LSN of the checkpoint is not logged but it will be visible in pg_controldata output as 0/DEAD. This value is invalid because PostgreSQL always skips the first WAL segment when initializing a cluster.
Connections are established using the "happy eyeballs" approach from RFC 8305, i.e. new addresses (if available) are tried if the prior address has already had a reasonable time to connect. This prevents waiting too long on a failed connection but does not try all the addresses at once. Prior connections that are still waiting are rechecked periodically if no subsequent connection is successful.
This improves substantially on 39bb8a0, which failed to take into account connection attempts that do not fail (but never connect) and use up all the available time.
This saves about 16KiB in the binary and reduces exported symbols by about 75%. All variables are still exported and any functions that are referenced by their pointers or extern'd but never used outside the module where they are defined.
In addition to modest space savings, this should also increase performance a bit since the compiler can simplify calls to these functions and load the binary should also be a little faster.
The GCC documentation does not make it clear that visibility can be used with variables, but it certainly makes a difference in the binary size, so something is happening. Other sources on the internet suggest that visibility can be used with variables. Clearly exports are not affected, but there may be some other optimization happening.
Meson has a lot of advantages over autoconf/make, primarily in ease-of-use and performance. Make meson the only build system used for testing and building the Debian documentation, but leave the RHEL documentation using autoconf/make for now so it gets some testing.
Resume does not work correctly with delta diff/incr backups because the presence of a reference causes it to remove the file with the idea that it can just be referenced again. This is true for timestamp-based backups but for deltas all existing files need to be rechecked (which requires a reference).
This is fixable but not without significant effort and new tests and it calls into question the usefulness of non-full resumes. For diff/incr, if the file was changed since the prior backup there is a good chance it will be modified again before the resume occurs.
In order to keep this feature as useful as possible for the most valuable case, limit resumes to full backups.
02eea55 added code to load a buffer of data from a file being backup up to detect files that have been truncated to zero after manifest generation. This mechanism can also be used to detect files that have not changed since the prior backup.
If the result of the file copy fits into a single buffer, then the size and checksum can be compared to the prior file before anything gets stored. If the file matches then it is referenced to the file in to prior backup.
The size that can be compared for normal copies is limited by the buffer size but for block incremental it works with any size file since there is no output from block incremental when the file is identical.
Infer the size of all WAL segments from the size of the first segment rather than getting info for all segments (up to queue size). If the segments are not the same size then there are larger issues than the WAL queue.
storageListP() returns a list of entries in a path and should not need to stat/head, etc. in order to get more detailed info. This was broken by 75623d4 which failed to set the level correctly.
Set the correct level and update tests.
There's no easy way to directly test for a regression here but the SFTP tests will fail if more detailed info is requested since it would require script changes.
a42614e introduced the capability to preserve smaller than expected files for block incremental restore delta, but failed to take into account that zero-length files are both useless and cause the block checksum filter to error.
Fix this by skipping zero-length files during block incremental restore delta.
Update references to recovery.conf to include postgresql.auto.conf used in newer versions.
Also update a broken recovery URL and point it to the current version (with a hint to select the proper version of PostgreSQL).
c8264291 added libbacktrace to the meson build (not used in production yet), but held off on adding it to autoconf/make before more performance testing was done.
Performance tests show there is no noticeable cost to adding libbacktrace, so add it to get more detail error stack traces.
It is a bit confusing that --help and --version do not work like most command-line programs. For example, git allows either --help or help.
Make these work by making them shortcuts (not actual options) to the applicable commands.
The user will still need to use help (not --help) to get help on specific commands/options, but at least they can get to the main help (which will tell them this) via --help.
Bug Fixes:
* Fix short read in block incremental restore. (Reviewed by Stephen Frost, Brent Graveland. Reported by Adol Rodriguez, Brent Graveland.)
* Fix overflow suppressing backup progress in info output. (Fixed by Robert Donovan. Reviewed by Joe Wildish.)
Improvements:
* Preserve partial files during block incremental delta restore. (Reviewed by Stephen Frost.)
* Add support for alternate compile-time page sizes. (Contributed by Viktor Kurilko. Reviewed by David Steele.)
* Skip files truncated during backup when bundling. (Contributed by Georgy Shelkovy. Reviewed by David Steele.)
* Improve SFTP storage error messages. (Contributed by Reid Thompson. Reviewed by David Steele.)
Use storageSftpEvalLibSsh2Error() in more locations to provide better error information. Also add storageSftpLibSsh2SessionLastError() for the same reason.
During restore it is possible to read all the blocks out of a compressed super block without reading all the input. This is because the compression format may have some trailing bytes that are not required for decompression but are required to indicate that data has ended. If a buffer aligned with the compressed data in a certain way, these last bytes might not be read.
Explicitly read out any final bytes at the end of each super block to handle this case. This should always result in no additional data out and we check for that, but it does move the read position to the beginning of the next compressed super block so decompression can begin without error.
Refactor 02eea555 to always close the file immediately on EOF and use backupCopyResultCopy to continue processing. Closing the file immediately saves a later EOF check and is friendlier to added logic in this area. Using backupCopyResultCopy to continue is clearer also makes it easier to add new logic.
Also store zero checksum so the bulk of results collection can be moved within the copy block.
This allows less duplication of buffers.
For delta check return file->pgFileSize/file->pgFileChecksum instead of pgTestSize/pgTestChecksum since this saves one buffer duplication and we know these values are equal since we just checked them.
Also add an assert to ensure copyChecksum is valid relative to size.
If a file stored with block incremental shrinks below the prior block size then the map is useless and the entire file needs to be stored again.
In this case use the new block incremental values (even if none) rather than preserving the old ones.
Previously files that were smaller than the expected size were not preserved for block incremental, even though it is possible that block incremental could make use of a partial file.
One example is when a restore encounters an error. On retry the partial file can be used as a starting point rather than copying again from the beginning. Another example is restoring a backup where a file is larger than what already exists in the data directory.
Preserve any size file when block incremental will be used for the delta in order to reuse partial files when possible. If the file is smaller than expected then disable the whole-file checksum to reduce overhead.
This refactor should provide more clarity on what factors affect an incremental, rather that just having one big expression do it all. Overall this may be slightly more efficient since some values are reused that before were recalculated.
No behavioral changes are introduced.
Writing the sz and szCplt parameters in the lock file used jsonWriteUInt64() but reading these parameters used jsonReadUInt(). This caused a silent exception for any backups larger than MAX_UINT and prevented the info command from reporting progress.
Correct this so the reads are symmetric and verified before/after with a test.
In bundle mode pgBackRest skips files of zero size, that is, it does not queue them for copying.
After splitting the files into bundles, pgBackRest launches one or more processes that directly perform the backup, namely, read the files and, if necessary, write them to the bundles.
If during the time between the distribution of all files among bundles and the direct copying of a file to a bundle, this file of non-zero size was truncated to zero size (for example, when the table was truncated), then pgBackRest still unconditionally places such a zero-size file in the bundle, taking up space in it equal to the size of the headings, and additionally writes the original file size to the manifest.
In debug build an assertion was added, that does not allow zero-size files to be written to bundles, which leads to an error.
To solve the problem, this patch, when reading the next file, loads one buffer from the file to detect if it is zero-size. If so it marks the file as truncated and continues on to the next file.
The advantages of the solution are that, firstly, the assert will not fire on debug builds, and secondly, we will not place zero-size files in bundles, which exactly corresponds to the specification.
The patch adds the backupCopyResultTruncate value to the BackupCopyResult enumeration to use it to indicate the result when a non-zero size file is truncated to zero size during the backup process.
Alternate pages sizes can be selected at compile-time, .e.g. 4096. While compile-time settings are generally not well tested by core, some established forks such as Greenplum use them.
