PIP-264

Motivation

Adds producer related metrics to the OpenTelemetry pipeline.

Modifications

• Adds the metrics described in [feat][doc] PIP-264: Add OpenTelemetry producer metrics reference pulsar-site#911 to the collector runs.
• Relocates the metric backend data-sources (Producer#msgIn, Producer#chunkedMessageRate and Producer#msgDrop) from the Producer class to PublisherStatsImpl and NonPersistentPublisherStatsImpl, for a cleaner design.
• Add field Rate.totalValueAdder keeping track of cumulative values added to the Rate, further simplifying the design.

Verifying this change

• Make sure that the change passes the CI checks.

This change added tests and can be verified as follows:

• Added basic messaging test in OpenTelemetryProducerStatsTest
• Updated existing test `` to cover the message drop counter functionality

Does this pull request potentially affect one of the following parts:

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics: As described in [feat][doc] PIP-264: Add OpenTelemetry producer metrics reference pulsar-site#911
• Anything that affects deployment

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

Matching PR in forked repository

PR in forked repository: dragosvictor#25