rts: add activity logging to give context for resource usage reports

[marksvc]

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Open in Devin Review

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This change is 

[marksvc]

This branch has task/rts-connect as the merge target, as it is built no that branch. That branch will need to be merged before this PR can be.

[codecov]

Codecov Report

❌ Patch coverage is 92.00000% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.11%. Comparing base (f6c872f) to head (2dff5e5).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/RealtimeServer/common/realtime-server.ts	85.71%	7 Missing ⚠️
src/RealtimeServer/common/activity-logger.ts	92.42%	5 Missing ⚠️

Additional details and impacted files

@@                 Coverage Diff                  @@
##           task/rts-connect    #4061      +/-   ##
====================================================
+ Coverage             81.10%   81.11%   +0.01%     
====================================================
  Files                   661      664       +3     
  Lines                 43061    43192     +131     
  Branches               7054     7094      +40     
====================================================
+ Hits                  34925    35036     +111     
- Misses                 6963     6984      +21     
+ Partials               1173     1172       -1     

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[marksvc]

src/RealtimeServer/common/index.ts line 343 at r1 (raw file):

    }
    const conn = connections.get(handle);
    conn?.fetchSnapshotByTimestamp(collection, id, timestamp, (err, snapshot) => {

Devin posted a concern about this. The main problem is pre-existing, and I am drafting a fix for it to go into a separate PR. (null conn never calls callback)

[marksvc]

src/RealtimeServer/common/realtime-server.ts line 428 at r1 (raw file):

        opsCount = 0;
      }
      ActivityLogger.instance.log('opSubmitted', {

Devin has expressed some concern about incompleteness of the logging, such as if an op submission is later rejected for permission reasons. In practice, the activity logger needs to show where the heavy or frequent activity is happening, rather than infrequent or special situations.

There may be some logging that is missing that would be relevant for identifying heavy activity. So that's something to keep an eye out for.

[marksvc]

src/RealtimeServer/common/activity-logger.ts line 19 at r1 (raw file):

}

const DEFAULT_LOG_LEVEL: RtsLogLevel = 'none';

Devin mentions that there is no log bound or rotation. I had a look at this and it looks like it shouldn't be too challenging to set up if we need it. We can do it at the system level; it looks like the application doesn't need additional changes to make that possible.

[marksvc]

src/RealtimeServer/common/activity-logger.ts line 112 at r1 (raw file):

          .map(batchEntry => JSON.stringify(batchEntry) + '\n')
          .join('');
        await appendFile(this.logPath, lines, { flag: 'a' });

Devin is concerned about multiple processes writing to the log at the same time. We only run one RealtimeServer at a time.