* Add Min() interface - rename MaxSumCount to MinMaxSumCount
Fixes https://github.com/open-telemetry/opentelemetry-go/issues/319
* update stdout exporter to collect and output the minimum value
* update min and max atomically in Aggregator Update
* changed all references to maxsumcount to minmaxsumcount
* Address PR comments
* Add tests for nonabsolute and varying sign values
* Implement support for NonAbsolute Measurement MaxSumCount
Previously, the MaxSumCount aggregator failed to work correctly with
negative numbers (e.g. MeasureKind Alternate()==true).
* Pass NumberKind to MaxSumCount New() function
Allows it to set the initial state (current.max) to the correct value
based on the NumberKind.
* Revert extraneous local change
* Pass full descriptor to msc New()
This is analagous to the DDSketch New() constructor
* Remember to run make precommit first
* Add tests for empty checkpoint of MaxSumCount aggregator
An empty checkpoint should have Sum() == 0, Count() == 0 and Max()
still equal to the numberKind.Minimum()
* Return ErrEmptyDataSet if no value set by the aggregator
Remove TODO from stdout exporter to ensure that if a maxsumcount or
ddsketch aggregator returns ErrEmptyDataSet from Max(), then the
entire record will be skipped by the exporter.
Added tests to ensure the exporter doesn't send any updates for
EmptyDataSet checkpoints - for both ddsketch and maxsumcount.
* Relayout Aggreggator struct to ensure int64s are 8-byte aligned
On 32-bit architectures, Go only guarantees that primitive
values are aligned to a 4 byte boundary. Atomic operations on 32-bit
machines require 8-byte alignment.
See https://github.com/golang/go/issues/599
* Addressing PR comments
The use of Minimum() for the default uninitialized Maximum value means
that in the unlikely condition that every recorded value for a measure
is equal to the same NumberKind.Minimum(), then the aggregator's Max()
will return ErrEmptyDataSet
* Fix PR merge issue
* Add MetricAggregator.Merge() implementations
* Update from feedback
* Type
* Ckpt
* Ckpt
* Add push controller
* Ckpt
* Add aggregator interfaces, stdout encoder
* Modify basic main.go
* Main is working
* Batch stdout output
* Sum udpate
* Rename stdout
* Add stateless/stateful Batcher options
* Undo a for-loop in the example, remove a done TODO
* Update imports
* Add note
* Rename defaultkeys
* Support variable label encoder to speed OpenMetrics/Statsd export
* Lint
* Doc
* Precommit/lint
* Simplify Aggregator API
* Record->Identifier
* Remove export.Record a.k.a. Identifier
* Checkpoint
* Propagate errors to the SDK, remove a bunch of 'TODO warn'
* Checkpoint
* Introduce export.Labels
* Comments in export/metric.go
* Comment
* More merge
* More doc
* Complete example
* Lint fixes
* Add a testable example
* Lint
* Let Export return an error
* add a basic stdout exporter test
* Add measure test; fix aggregator APIs
* Use JSON numbers, not strings
* Test stdout exporter error
* Add a test for the call to RangeTest
* Add error handler API to improve correctness test; return errors from RecordOne
* Undo the previous -- do not expose errors
* Add simple selector variations, test
* Repair examples
* Test push controller error handling
* Add SDK label encoder tests
* Add a defaultkeys batcher test
* Add an ungrouped batcher test
* Lint new tests
* Respond to krnowak's feedback
* Undo comment
* Use concrete receivers for export records and labels, since the constructors return structs not pointers
* Bug fix for stateful batchers; clone an aggregator for long term storage
* Remove TODO addressed in #318
* Add errors to all aggregator interfaces
* Handle ErrNoLastValue case in stdout exporter
* Move aggregator API into sdk/export/metric/aggregator
* Update all aggregator exported-method comments
* Document the aggregator APIs
* More aggregator comments
* Add multiple updates to the ungrouped test
* Fixes for feedback from Gustavo and Liz
* Producer->CheckpointSet; add FinishedCollection
* Process takes an export.Record
* ReadCheckpoint->CheckpointSet
* EncodeLabels->Encode
* Format a better inconsistent type error; add more aggregator API tests
* More RangeTest test coverage
* Make benbjohnson/clock a test-only dependency
* Handle ErrNoLastValue in stress_test
* Array aggregator part 1
* Improve median testing
* More testing
* More testing
* Update other dist tests
* Add to the benchmark
* Move errors into aggregator package, use from ddsketch; update Max/Min/Quantile to return errors for array/ddsketch/maxsumcount
* Lint
* Test non-absolute ddsketch
* Lint
* Comment
* Add note
