Postgres test-connection fails because replication-byte metric is not registered

[crspi]

Summary

The test-connection command fails for an otherwise-valid PostgreSQL replication configuration before it can report the connection result.

test-connection registers a ReplicationEngine, but TEST_CONNECTION mode receives no replication metrics. PostgresModule then installs a pgwire byte recorder that accesses an unregistered DATA_REPLICATED_BYTES counter.

Environment

• Runtime failure reproduced with PowerSync Service v1.23.3, pinned to OCI digest sha256:b6b22fa7d0d862f04bdff62846e656756d17bcf3dd6eca399a0633671051438b
• PostgreSQL replication source
• The five causal files are unchanged in stable v1.24.0, prerelease v1.25.0, and current main at d3216be9f1f285fd4f2622a7d987ebaf4c2b8e0c

Reproduction

Use an otherwise-valid self-hosted configuration containing a PostgreSQL replication connection:

docker run --rm \
  -v "$PWD/powersync.yaml:/config/powersync.yaml:ro" \
  journeyapps/powersync-service:1.23.3@sha256:b6b22fa7d0d862f04bdff62846e656756d17bcf3dd6eca399a0633671051438b \
  test-connection --config-path /config/powersync.yaml

Actual result

The command exits nonzero with:

PSYNC_S0001: Counter powersync_data_replicated_bytes_total has not been created and registered yet.

Expected result

The command should complete its PostgreSQL connection and permission checks and report their actual result.

Source trail in v1.24.0

• test-connection selects TEST_CONNECTION mode and registers ReplicationEngine
• TEST_CONNECTION is absent from the metrics-mode map
• Replication counters are created only for MetricModes.REPLICATION
• The PostgreSQL recorder accesses DATA_REPLICATED_BYTES whenever a replication engine exists
• Missing counters throw ServiceAssertionError

Impact

This makes the service CLI unsuitable as a PostgreSQL readiness or deployment gate, even when the database configuration itself is valid.

Possible fixes appear to be either registering replication metrics for TEST_CONNECTION or avoiding the PostgreSQL replication-byte recorder in this mode. Which behavior is intended for test-connection?

[rkistner]

Thanks for the report; I confirmed the issue. I haven't yet checked what the best fix is, but we don't need the metrics for test-connection.

We should also test this command on CI - I assume it has been broken for quite a while now.