Adding Percentiles to Beam Distribution Metric

[ajothomas]

Problem

This PR intends to add percentiles to beam distribution metric

Motivation

• Percentile metrics is a commonly requested feature from Beam pipeline users
• Distribution metrics in Samza runner are currently not wired to Samza's MetricsRegistry

Proposed Changes

• DistributionData currently contains the logic for computing distributions. Datasketches library has been used for percentile computation which uses a sketch based approach under the hood. https://datasketches.apache.org/
• DistributionResult will report a map of percentiles and percentile values.
• Wire all distribution metrics as Gauges in Samza MetricsRegistry in Samza runner

API Changes

• Removed method public void update(long sum, long count, long min, long max) from Distribution Metric code as it seems to be dead code.

Testing

• Tests for MetricsContainer, DistributionCell, etc
• ValidateRunner tests to validate MetricsTest for different runners

---

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ValidatesRunner compliance status (on master branch)

Lang	ULR	Dataflow	Flink	Samza	Spark	Twister2
Go	---					---
Java
Python	---					---
XLang						---

Examples testing status on various runners

Lang	ULR	Dataflow	Flink	Samza	Spark	Twister2
Go	---	---	---	---	---	---	---
Java	---		---	---	---	---	---
Python	---	---	---	---	---	---	---
XLang	---	---	---	---	---	---	---

Post-Commit SDK/Transform Integration Tests Status (on master branch)

Go	Java	Python

Pre-Commit Tests Status (on master branch)

---	Java	Python	Go	Website	Whitespace	Typescript
Non-portable
Portable	---			---	---	---

See .test-infra/jenkins/README for trigger phrase, status and link of all Jenkins jobs.

GitHub Actions Tests Status (on master branch)

See CI.md for more information about GitHub Actions CI.

[xinyuiscool]

LGTM! Thanks fore adding this metric!

[kw2542]

LGTM

[xinyuiscool]

Do the empty check here.

[xinyuiscool]

LGTM! Thanks for the update.