Ian Boston created SLING-4849:
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Summary: Create Metrics instumentation bundle using ASM.
Key: SLING-4849
URL: https://issues.apache.org/jira/browse/SLING-4849
Project: Sling
Issue Type: Improvement
Components: Extensions
Reporter: Ian Boston
Assignee: Ian Boston
Aim: To enable metrics for any method call in a Sling JVM without requiring any
code changes to existing bundles.
Method: OSGi 4.3 has a WeavingHook which is allows a byte code generator to get
in between the classloader and classloading. Using ASM it should be possible to
write code that enhances the byte code of any class to wrap method calls in
calls to the Dropwizard Metrics library. This should work without any changes
to the startup. The only requirement is the bundle is loaded before the
classloader loads the classes that need to be instrumented.
Quick tests indicate the method works and adds no more than 10 byte code
instructions to a method. It may be possible to reduce that further.
Instrumentation will be controlled by configuration, so classes that are not
instrumented are not modified at all when loading.
The metrics once available can be pushed into Graphite, Kibana or some other
collection service. Dumped to a file periodically or exposed in JMX as counters.
Will work in a branch on github initially.
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