NIFI-4169: Enhance PutWebSocket error handling

[ijokarumawak]

NOTE
Submitting this PR just for code review purpose. Not ready to be merged yet.

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[ijokarumawak]

This PR is now ready to get reviewed.

A flow template is available here for testing both NiFi as a WebSocket client and server.
https://gist.github.com/ijokarumawak/f36668b193bc413da3e0d968bb6b47c1

This PR is based on the contribution from Y Wikander.

• Added "Fork Failed Broadcast Sessions" property to specify whether
  failed FlowFiles should be forked and transferred individually so that
  user can construct a error handling flow using each session id.
• Added "Enable Detailed Failure Relationships" property to separate
  failure routes into more detailed ones, such as 'no connected sessions'
  or 'communication failure'
• Added "websocket.broadcast.succeeded" and "websocket.broadcast.failed"
  attributes to outgoing FlowFiles when a message is broadcast.

[EmilioCC]

Would be nice to have this included in the next release.

[alopresto]

Unfortunately there are branch conflicts which will require some attention as well as performing an actual review. As the next release candidate is probably being cut as we speak, this will not make it in to 1.9.0.

[EmilioCC]

Let's say I resolve the merge conflict, who will perform the actual review? This is an old pull request. It might get other conflicts in the next 2 years.

[joewitt]

The merge conflict looks pretty easy to resolve. What is often harder is finding someone to review it. Reviews do not have to be done by a committer - it only requires a committer to do the final merge. You volunteering to do a test/review would be most valuable.

[EmilioCC]

It would be my first time contributing to NiFi. Actually, it would be the first time I contribute to an ASF project. Is the process of reviewing really what is explained here https://cwiki.apache.org/confluence/display/NIFI/Contributor+Guide#ContributorGuide-CodeReviewProcess ? I would need a bit of guidance if it's not what you guys actually do.

[ijokarumawak]

@EmilioCC Thanks for your interest for this PR and excuse my slow response. I've rebased this PR with the latest master to resolve conflicts. (I hope you haven't tried it yourself yet..)
If you have time, please review the changes.

Actually, this change has originally initiated by Y Wikander a year ago. And I added additional commit while I was reviewing that.
I haven't merged this because I haven't got +1 from anyone else.
If you can give your +1, then I will merge this. Thanks!

[EmilioCC]

@ijokarumawak I'll review it first and look at the failing tests. It looks like you have few tests that are failing for those new changes. I'll give you my +1 soon!

[ijokarumawak]

@EmilioCC Updated the failing tests. Thanks!

[ijokarumawak]

Hi @EmilioCC, just wanted to check if there's any issue to test this PR. Hope everything is working fine for you. Thanks!

[github-actions]

We're marking this PR as stale due to lack of updates in the past few months. If after another couple of weeks the stale label has not been removed this PR will be closed. This stale marker and eventual auto close does not indicate a judgement of the PR just lack of reviewer bandwidth and helps us keep the PR queue more manageable. If you would like this PR re-opened you can do so and a committer can remove the stale tag. Or you can open a new PR. Try to help review other PRs to increase PR review bandwidth which in turn helps yours.