Cameron Lee created SAMZA-2671:
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Summary: Clean up how Samza wires metrics and handles lifecycle of
metrics objects
Key: SAMZA-2671
URL: https://issues.apache.org/jira/browse/SAMZA-2671
Project: Samza
Issue Type: Improvement
Reporter: Cameron Lee
There is some opportunity for improvement in how Samza code handles metrics:
# Use more dependency injection: There are multiple places where metrics
registries (see "MetricsRegistryMap" constructor) and metrics reporters (see
"MetricsReporterLoader.getMetricsReporters") get created. Ideally, this should
not be necessary.
# Clean up metrics registration: "MetricsReporter.register" gets called in too
many places, so it is hard to track when it is happening.
# Define ordering for "MetricsReporter.register" and "MetricsReporter.start":
It looks like there is no contract on the ordering of
"MetricsReporter.register" and "MetricsReporter.start". Some implementations
might assume an ordering while others don't. We should clarify that.
# Improve lifecycle management code flow for "MetricsReporter.register" and
"MetricsReporter.start": It looks like the current code attempts to do all
"register" calls before any "start" call. Therefore, the reporters need to be
started somewhat deep into the lifecycle of the Samza components in general. It
is hard to keep track of when this happens for each separate component. For
example, for "ClusterBasedJobCoordinator", "MetricsReporter.start" gets called
inside "ContainerProcessManager.start", but that's not obvious unless someone
steps into the code flow.
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