[HDDS-1116] Add java profiler servlet to the Ozone web servers

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.4.0
• Labels: pull-request-available
• Target Version/s: 0.4.0
• Assignee: Marton Elek
• Reporter: Marton Elek
• Created: 15/Feb/19 14:40
• Updated: 16/Mar/21 03:09
• Resolved: 15/Feb/19 19:41

Description

Thanks to gopalv we learned that prasanth_j implemented a helper servlet in Hive to initialize new async profiler sessions and provide the svg based flame graph over HTTP. (see HIVE-20202)

It seems to very useful as with this approach the profiling could be very easy.

This patch imports the servlet from the Hive code base to the Ozone code base with minor modification (to make it work with our servlet containers)

• The two servlets are unified to one
• Streaming the svg to the browser based on IOUtils.copy
• Output message is improved

By default the profile servlet is turned off, but you can enable it with 'hdds.profiler.endpoint.enabled=true' ozone-site.xml settings. In that case you can access the /prof endpoint from scm,om,s3g.

You should upload the async profiler first (https://github.com/jvm-profiling-tools/async-profiler) and set the ASYNC_PROFILER_HOME environment variable to find it.

Issue Links

• relates to: HDDS-4984 Async profiler 2.0 no longer supports svg output
• links to: GitHub Pull Request #491