Correlation log for precise message tracing on Join/Split node

[k-toumura]

• [ ] Bugfix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)

Proposed changes

For precise tracing for nodes which splitting or joining the messages, these nodes should emit a correlation log to provide information of which message is depend on another message. This PR add a new correlate metric event to Join/Split node.

For detailed information, see design note (not yet merged).

Checklist

• [x] I have read the contribution guidelines
• [x] For non-bugfix PRs, I have discussed this change on the forum/slack team.
• [x] I have run grunt to verify the unit tests pass
• [ ] I have added suitable unit tests to cover the new/changed functionality

[coveralls]

Coverage increased (+1.003%) to 68.6% when pulling 7d95c67492be6788a7df1833fff4d707940bf565 on node-red-hitachi:dev-splitcor into 26d83bb9eaa762165c14970eb8bfb1fbc04dab73 on node-red:dev.

[knolleary]

Thanks for this @k-toumura

It would be helpful to have some unit tests for this new logic as it is quite complicated and could get broken if we are not careful in the future.

[linux-foundation-easycla[bot]]

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• :white_check_mark: login: k-toumura / name: Kunihiko Toumura (e994b9d5e123f09e8d0b4446b040c5c338abe9aa, f350423a0093e1fb216223b80c10f1010f9b1781, 7d95c67492be6788a7df1833fff4d707940bf565)