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https://issues.apache.org/jira/browse/STORM-3163?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mal Graty updated STORM-3163:
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Summary: ShellLogHandler loses thread context between setup and use (was:
ShellLogHandler setup should be done on the same thread that uses it)
> ShellLogHandler loses thread context between setup and use
> ----------------------------------------------------------
>
> Key: STORM-3163
> URL: https://issues.apache.org/jira/browse/STORM-3163
> Project: Apache Storm
> Issue Type: Bug
> Components: storm-core
> Affects Versions: 1.2.2
> Reporter: Mal Graty
> Priority: Trivial
> Labels: Logging
>
> `ShellBolt` instantiates the `ShellLogHandler` and calls its `setUpContext`
> as part of `prepare`, immediately before it spawns its `BoltReaderRunnable`
> and `BoltWriterRunnable` threads which are responsible for communication with
> the `ShellProcess` that's already been spawned.
> The `ShellLogHandler` is used exclusively from `BoltReaderRunnable`. The
> upshot of this is that `setUpContext` is executed in the task thread (i.e.
> `Thread-21-joiner-executor[2 2]`) while the `log` method is executed in the
> anonymous thread (i.e. `Thread-30`) running the `BoltReaderRunnable`.
> This creates a problem when trying to leverage `slf4j`'s `MDC` (or `NDC`)
> which are used for augmenting log messages with additional information which
> is localised and persisted at the thread level.
> The current work around for this is to store all relevant context on the
> `ShellLogHandler` during `setUpContext`, and then write it into the `MDC`
> during the `log` call, and taking precautions around that state being thread
> safe. The thread safety requirement is the first drawback, the second is that
> each `log` call has the additional overhead of either unconditionally writing
> to the `MDC` or checking that the `MDC` is already populated. Neither is very
> appealing.
> The suggested solution is to pass `stormConf`, `_process`, and `_context`
> into the constructor of `BoltReaderRunnable` (and perhaps also
> `BoltWriterRunnable`) and instantiate `ShellLogHandler` and call its
> `setUpContext` from that thread.
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