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https://issues.apache.org/jira/browse/HBASE-21926?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16794297#comment-16794297
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Andrew Purtell commented on HBASE-21926:
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I’m using Eclipse as IDE with the HBase formatter from dev-support and it’s not
always getting it right as far as checkstyle is concerned. I think there is an
additional complication that edits in place to go back and forth between shaded
and unshaded dependencies depending on code line can trigger warnings if you
don’t think to remove the lines and let the IDE place them. (But see first
point.)
Frankly I see little value in ImportOrder beyond the strictest of pedantry.
> Profiler servlet
> ----------------
>
> Key: HBASE-21926
> URL: https://issues.apache.org/jira/browse/HBASE-21926
> Project: HBase
> Issue Type: New Feature
> Components: master, Operability, regionserver
> Reporter: Andrew Purtell
> Assignee: Andrew Purtell
> Priority: Major
> Fix For: 3.0.0, 1.5.0, 2.3.0
>
> Attachments: 1.png, 2.png, 3.png, 4.png, HBASE-21926-branch-1.patch,
> HBASE-21926-branch-1.patch, HBASE-21926-branch-1.patch, HBASE-21926.patch,
> HBASE-21926.patch, HBASE-21926.patch
>
>
> HIVE-20202 describes how Hive added a web endpoint for online in production
> profiling based on async-profiler. The endpoint was added as a servlet to
> httpserver and supports retrieval of flamegraphs compiled from the profiler
> trace. Async profiler
> ([https://github.com/jvm-profiling-tools/async-profiler] ) can also profile
> heap allocations, lock contention, and HW performance counters in addition to
> CPU.
> The profiling overhead is pretty low and is safe to run in production. The
> async-profiler project measured and describes CPU and memory overheads on
> these issues:
> [https://github.com/jvm-profiling-tools/async-profiler/issues/14] and
> [https://github.com/jvm-profiling-tools/async-profiler/issues/131]
> We have an httpserver based servlet stack so we can use HIVE-20202 as an
> implementation template for a similar feature for HBase daemons. Ideally we
> achieve these requirements:
> * Retrieve flamegraph SVG generated from latest profile trace.
> * Online enable and disable of profiling activity. (async-profiler does not
> do instrumentation based profiling so this should not cause the code gen
> related perf problems of that other approach and can be safely toggled on and
> off while under production load.)
> * CPU profiling.
> * ALLOCATION profiling.
>
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