Add Cassandra compaction progress metrics via JMX handler

[jkoronaAtCisco]

Description:

Adds two new Cassandra gauges to the JMX scraper:

• cassandra.compaction.progress.bytes — bytes completed for in-flight compactions
• cassandra.compaction.progress.total — total bytes for in-flight compactions

Both metrics carry taskType, keyspace, and columnfamily attributes and are grouped by that composite key. Only compactions measured in bytes are reported. Values are summed across parallel compaction tasks sharing the same key.

Implemented as a code-based ExperimentalJmxMetricHandler (SPI introduced in opentelemetry-java-instrumentation 2.29.0) because the Compactions MBean attribute requires iteration, grouping, and BigInteger string parsing — none of which can be expressed in declarative YAML rules.

Testing:

Unit tests added to cover new CassandraCompactionProgressHandler.

The Cassandra integration test was refactored to reliably produce visible compaction activity: data seeding now happens before the scraper starts, and compaction is triggered only after the scraper is running, eliminating a race condition in the original approach.

Notes:

Action required before merge: dependencyManagement/build.gradle.kts currently pins otelInstrumentationVersion = "2.29.0-alpha-SNAPSHOT". This must be updated to the stable published release (e.g. 2.29.0-alpha) before the PR is submitted, as SNAPSHOT versions are non-deterministic across CI builds and do not resolve from Maven Central.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds Cassandra compaction byte-progress metrics to the JMX scraper via a new code-based handler, and wires it into the Cassandra target system configuration and tests.

Changes:

• Introduces CassandraCompactionProgressHandler emitting cassandra.compaction.progress.bytes / .total grouped by taskType, keyspace, columnfamily.
• Registers the handler via Java SPI and Cassandra YAML, and adds unit + integration test coverage.
• Adds an integration-test lifecycle hook to trigger long-running compactions after the scraper starts.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
jmx-scraper/src/main/java/io/opentelemetry/contrib/jmxscraper/handler/CassandraCompactionProgressHandler.java	New handler that queries Cassandra CompactionManager and emits progress gauges.
jmx-scraper/src/main/resources/META-INF/services/io.opentelemetry.instrumentation.jmx.internal.ExperimentalJmxMetricHandler	Registers the new handler via ServiceLoader.
jmx-scraper/src/main/resources/cassandra.yaml	Enables the handler for the Cassandra target system.
jmx-scraper/src/test/java/io/opentelemetry/contrib/jmxscraper/handler/CassandraCompactionProgressHandlerTest.java	Adds unit tests for grouping/parsing/skipping behavior.
jmx-scraper/src/integrationTest/java/io/opentelemetry/contrib/jmxscraper/target_systems/TargetSystemIntegrationTest.java	Adds an afterScraperStarted hook to support target-side actions post-start.
jmx-scraper/src/integrationTest/java/io/opentelemetry/contrib/jmxscraper/target_systems/CassandraIntegrationTest.java	Seeds data + triggers compaction to validate new progress metrics in integration tests.
jmx-scraper/build.gradle.kts	Adds Mockito dependency for new unit tests.
dependencyManagement/build.gradle.kts	Updates instrumentation version to a SNAPSHOT.
CHANGELOG.md	Documents the new compaction progress metrics.

[jkoronaAtCisco]

As mentioned in PR description, stable release is not released yet. Will updated it asap.