Flaky test: publication_manager_test race condition in relay tracker restart

[alco]

Summary

The test "handles relation tracker restart" in publication_manager_test.exs:503 has a race condition that causes intermittent CI failures.

Observed in run 22354924262 on main (2026-02-24).

Error

** (exit) exited in: GenServer.call({:via, Registry, {:"Electric.ProcessRegistry:...", {Electric.Replication.PublicationManager.RelationTracker, nil}}}, {:remove_shape, "36215155-..."}, 5000)
    ** (EXIT) no process: the process is not alive or there's no process currently associated with the given name

Root Cause

The test at test/electric/replication/publication_manager_test.exs:503:

1. Line 515: GenServer.stop(relation_tracker_name) kills the RelationTracker
2. Line 519: assert_pub_tables(ctx, [ctx.relation], 2_000) polls Postgres publication tables until they match
3. Line 522: PublicationManager.remove_shape(ctx.stack_id, shape_handle) does a GenServer.call to the RelationTracker

The problem is that assert_pub_tables checks Postgres state, not whether the RelationTracker GenServer has been re-registered by the supervisor. There's a window where publication tables are correct (from the previous state) but the new RelationTracker process isn't yet alive or hasn't finished handle_continue(:restore_relations, ...).

Suggested Fix

Call RelationTracker.wait_for_restore(ctx.stack_id) before remove_shape on line 522. This function already exists (line 79-82 of relation_tracker.ex) and blocks until handle_continue(:restore_relations) completes, which guarantees the process is registered and ready.

Context: Broader CI Flakiness

While investigating, I looked at all sync-service workflow failures from the last 2 days: 12 failures vs 14 successes (~46% failure rate). The failures are spread across many test files — only 1 of the 12 was this publication_manager_test:

Test file	Failures
shape_cache_test.exs:501	4
request_batcher_test.exs:100	2
publication_manager_test.exs:503	1
api_test.exs:925	1
delete_shape_plug_test.exs:100	1
shape_db_test.exs:553	1
shape_cache_test.exs:877	1