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https://issues.apache.org/jira/browse/HADOOP-9090?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mostafa Elhemali updated HADOOP-9090:
-------------------------------------

    Attachment: HADOOP-9090.justEnhanceDefaultImpl.4.patch

(I highly appreciate the responsive feedback I'm getting from you Luke.)

Thanks - you raise good points. My fear was that do we want the immediate sinks 
to be queued up or not, and do we want to leave the queue thread hanging if the 
sink times out or not. I think though I was swayed to your way of thinking by 
two things: a) the flush() problem you point out and b) that my previous patch 
would've left sinks possible called by multiple threads instead of just the 
queue thread which can be bad.

I've implemented the spirit of what you said. I opted though to have the 
putMetricsImmediate() wait for its specific MetricsBuffer since I figured the 
way you had it may end up in race conditions if multiple threads are calling 
publishMetricsNow() at the same time. Let me know what you think - thanks!
                
> Refactor MetricsSystemImpl to allow for an on-demand publish system
> -------------------------------------------------------------------
>
>                 Key: HADOOP-9090
>                 URL: https://issues.apache.org/jira/browse/HADOOP-9090
>             Project: Hadoop Common
>          Issue Type: New Feature
>          Components: metrics
>            Reporter: Mostafa Elhemali
>            Priority: Minor
>         Attachments: HADOOP-9090.2.patch, 
> HADOOP-9090.justEnhanceDefaultImpl.2.patch, 
> HADOOP-9090.justEnhanceDefaultImpl.3.patch, 
> HADOOP-9090.justEnhanceDefaultImpl.4.patch, 
> HADOOP-9090.justEnhanceDefaultImpl.patch, HADOOP-9090.patch
>
>
> We have a need to publish metrics out of some short-living processes, which 
> is not really well-suited to the current metrics system implementation which 
> periodically publishes metrics asynchronously (a behavior that works great 
> for long-living processes). Of course I could write my own metrics system, 
> but it seems like such a waste to rewrite all the awesome code currently in 
> the MetricsSystemImpl and supporting classes.
> The way I'm proposing to solve this is to:
> 1. Refactor the MetricsSystemImpl class into an abstract base 
> MetricsSystemImpl class (common configuration and other code) and a concrete 
> PeriodicPublishMetricsSystemImpl class (timer thread).
> 2. Refactor the MetricsSinkAdapter class into an abstract base 
> MetricsSinkAdapter class (common configuration and other code) and a concrete 
> AsyncMetricsSinkAdapter class (asynchronous publishing using the SinkQueue).
> 3. Derive a new simple class OnDemandPublishMetricsSystemImpl from 
> MetricsSystemImpl, that just exposes a synchronous publish() method to do all 
> the work.
> 4. Derive a SyncMetricsSinkAdapter class from MetricsSinkAdapter to just 
> synchronously push metrics to the underlying sink.
> Does that sound reasonable? I'll attach the patch with all this coded up and 
> simple tests (could use some polish I guess, but wanted to get everyone's 
> opinion first). Notice that this is somewhat of a breaking change since 
> MetricsSystemImpl is public (although it's marked with 
> InterfaceAudience.Private); if the breaking change is a problem I could just 
> rename the refactored classes so that PeriodicPublishMetricsSystemImpl is 
> still called MetricsSystemImpl (and MetricsSystemImpl -> 
> BaseMetricsSystemImpl).

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