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https://issues.apache.org/jira/browse/HADOOP-3772?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12614504#action_12614504
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Doug Cutting commented on HADOOP-3772:
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This looks like a reasonable approach. A few nits:
It would be cleaner if TaskTracker.Instrumentation were a standalone class.
TaskTracker.java is already plenty big! Also, since it is public, this class
needs javadoc. The 'tt' field should be private w/ accessor methods or set by
the constructor. Should it be abstract? The reference to 'tt.mapTotal' should
be replaced with a call to a public method, etc.
Static accessor methods should be added to TaskTracker to get/set the
instrumentation impl, e.g.:
public static void setInstrumentation(Configuration conf, Class clazz) { ... }
public Class getInstrumentation(Configuration conf) { ... }
These should refer to a constant that names the configuration parameter name.
These methods should be used in preference to using the paramter name literal.
An entry should be added to hadoop-default.xml, documenting this new
configuration option.
> Proposed hadoop instrumentation API
> -----------------------------------
>
> Key: HADOOP-3772
> URL: https://issues.apache.org/jira/browse/HADOOP-3772
> Project: Hadoop Core
> Issue Type: Improvement
> Components: metrics
> Reporter: Ari Rabkin
> Attachments: instrumentation.patch
>
>
> We want to evolve the Hadoop metrics subsystem into a more generic
> Instrumentation facility. The ultimate goal is to add structured logging to
> Hadoop, with causal tags, a la X-trace. The existing metrics framework is
> not quite suitable for our needs, since the implementation and interface are
> tightly coupled. There's no way to use the metrics instrumentation points for
> anything other than metricss, and there's no way for a metrics context to
> find out what event just happened.
> We want to tease apart the generic notion of hookable instrumentation points,
> from the specifics of the information recording. The latter ought to be
> pluggable at run-time.
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