[shimoncohen]

LOGIC-4 of MAPCO-11317. Four independent correctness fixes.

Fixes

1. Config traversal — ConfigurationManager.GetChildren walked from the root section on every loop iteration (not the accumulated section) and its bounds re-applied the final key. Works for 2-part paths — which is the only current caller, GetChildren("TASK","types") — but silently wrong for 1-part and 3+-part paths. Now traverses the accumulated section.
2. Timer rethrow — HeartbeatClient.Send is a Timer.Elapsed handler that rethrew on failure. System.Timers.Timer discards it, and an unhandled exception on the timer thread can tear down the process. Now logs and lets the next tick retry.
3. Stack-trace reset — S3Client used throw e; on its non-key error paths, resetting the exception's stack trace. Changed to throw;.
4. Lock scope — Gpkg/Fs/S3 held their batch _locker as static, so every data-source instance serialized paging against every other instance. The guarded state is per-instance, so the lock is now per-instance. Also unblocks parallelism for SVC-1 (MAPCO-11325).

Testing

Full suite: 1141 passed, 0 failed. Fixes 1 and 4 preserve current behavior for existing call sites (2-part config path; single-instance paging) while correcting the latent/ cross-instance cases; 2 and 3 change only failure-path behavior. ConfigurationManager builds its IConfiguration from files in its ctor and isn't injectable, so GetChildren has no isolated unit test; the fix is exercised via the TaskRunner path.

🤖 Generated with Claude Code

[shimoncohen]

For the record re: the earlier note on ConfigurationManager.GetChildren (comment since deleted): simplified the section traversal to a colon-joined key lookup, matching GetConfiguration.

string key = string.Join(":", configPath);
return this.config.GetSection(key).GetChildren();

IConfiguration treats : as the hierarchy separator, so this nests through all path segments. Equivalent to the previous loop for the sole caller (GetChildren("TASK","types"), length 2) and correct for any path length — the earlier loop reassigned from the root each iteration, which would have dropped leading segments for length ≥ 3. Pushed in a follow-up commit.

[CL-SHLOMIKONCHA]

Approved, but I would reword this comment: System.Timers.Timer already swallows exceptions from Elapsed handlers, so the throw; was a no-op, not a crash risk.
HeartbeatClient.cs line 88

[shimoncohen]

@CL-SHLOMIKONCHA Heartbeat comment reworded in 73635c1: the Elapsed rethrow was a no-op since System.Timers.Timer swallows it; the catch now logs instead.