CDC troubleshooting - Arcyria

A failed run’s page shows the error and, for the errors below, a Fix line. A failed CDC run never confirms changes on the source, so the next run retries the same batch.

Error	Cause	Fix
`WAL_LEVEL_NOT_LOGICAL`	Logical decoding is off.	Set `wal_level = logical` (RDS/Aurora: `rds.logical_replication = 1`; Cloud SQL: `cloudsql.logical_decoding = on`) and restart.
`INSUFFICIENT_PRIVILEGE`	The user cannot use replication slots.	Grant `REPLICATION` (RDS/Aurora: `GRANT rds_replication`; Cloud SQL: `ALTER USER ... WITH REPLICATION`).
`POOLER_DETECTED`	The connection goes through a pooler.	Use the direct host and port. Supabase: Connect → Direct connection.
`NO_FREE_REPLICATION_SLOTS`	`max_replication_slots` is used up.	Drop unused slots or raise the limit and restart.
`SLOT_EXISTS`	A slot with this pipeline’s name belongs to something else.	Drop that slot on the source, then enable CDC again.
`SLOT_IN_USE`	Another connection is reading the slot.	Wait for the other run, or stop the other consumer.
`SLOT_INVALIDATED`	The source removed WAL the slot needed, for example because `max_slot_wal_keep_size` was reached.	Change data capture → Re-snapshot.
`SLOT_MISSING`	The slot was dropped outside Arcyria.	Change data capture → Re-snapshot.
`PUBLICATION_MISSING`	The publication does not exist.	Run the setup SQL from the CDC panel.
`PUBLICATION_MISSING_TABLE`	A CDC table is not in the publication, so its changes are not captured.	Run the `ALTER PUBLICATION ... ADD TABLE` statement shown in the error.
`TRUNCATE_DETECTED`	A TRUNCATE was captured and the stream’s truncate policy is Stop and ask.	Choose Ignore or Truncate the destination in the stream’s options, then run again.
`SCHEMA_CHANGE_DETECTED`	Source columns changed under the Fail the run policy.	Update the model or destination, then Accept source schema on the stream.
`CDC_KEY_MISSING`	The table has no primary key and no merge key.	Add a primary key, or set a merge key (a unique NOT NULL index).

Re-snapshot

Re-snapshot recovers from an invalidated or missing slot:

It clears the progress of every CDC stream, so each one reloads.
It drops the old slot.
It creates a new slot.

Destination rows are upserted, so reloading does not duplicate them.

Slot keeps growing

If the slot’s held WAL keeps growing:

make sure CDC runs are scheduled and succeeding;
check that the destination accepts the deliveries;
consider the heartbeat helper for quiet databases.

If the source must reclaim disk immediately, disable CDC to drop the slot.