[MongoDB Storage V3] Force create new replication stream if old one is invalidated

[rkistner]

When a replication stream is invalidated, for example due to a lost Postgres replication slot, or a MongoDB resume token falling outside the oplog window, we call restartReplication to start again from scratch. The implementation works by creating a copy of the current sync config.

The issue is that with incremental reprocessing on MongoDB storage v3, this is effectively a no-op. The fix is simple: Force creating a new replication stream, since there is no way we can recover within the existing replication stream. Unfortunately, there is no way to make incremental reprocessing work for us here.

The same applies to the two /process APIs., used by the dashboard "Defragment" action. In the future, we can investigate other ways to achieve the defragmenting goals.

Additional fixes

The comment here highlighted a class of issues, some existing before this PR: When we have one replication stream with both PROCESSING and ACTIVE sync configs, we must not update both sync configs to ERRORED. ERRORED is specifically used to keep serving the last ACTIVE stream to clients until we have a new one, so we should not have multiple.

This refactors the process both for restartReplication and for updateSyncRules to correctly handle that case, and additionally use transactions to be safe against concurrent modifications.

This changed the PR from a single forceNewReplicationStream flag to a much larger refactor.

Not many of the existing code issues could be reached directly, due to the original bug here "hiding" those issues. But these became directly apparent once we forced creating a new stream, which would then not correctly stop the existing ones in many cases.

AI Usage

Issue detected by Codex. Fix implemented by Codex gpt-5.6. Checked manually and using Claude Opus 5.

[changeset-bot]

🦋 Changeset detected

Latest commit: 1ddd04e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 12 packages

Name	Type
@powersync/service-module-mongodb-storage	Patch
@powersync/service-core	Patch
@powersync/service-schema	Patch
@powersync/service-module-convex	Patch
@powersync/service-module-mongodb	Patch
@powersync/service-module-mssql	Patch
@powersync/service-module-mysql	Patch
@powersync/service-module-postgres	Patch
@powersync/service-image	Patch
@powersync/service-module-core	Patch
@powersync/service-module-postgres-storage	Patch
test-client	Patch

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[stevensJourney]

The changes look solid and well explained to me. I could not think of any potential issues from this.