Raised in a source's producer process when a batch failed to commit.
This is deliberately a crash, not a handled error. A commit failure cannot be dead-lettered — writing the dead-letter row needs the same transaction that just failed — and it cannot be selectively skipped, because event-store acks are prefix-acks: acknowledging event N acknowledges everything before it, so a gap cannot be preserved.
The only correct response is to stop acknowledging and let the producer die. The event store rewinds the subscription to the last durable checkpoint when the subscriber process goes down, the supervisor restarts the producer, and the batch is redelivered. Events that did commit are filtered by source-side dedup on the way back through.
This is the transient path only
Restarting to replay is correct when the failure is transient — the database is unavailable, a deadlock was detected, a query was cancelled. It is not correct when the failure is deterministic, because replaying reproduces it identically and the loop never ends.
Scriba.Failure makes that distinction from SQLSTATE before this error is
ever raised, so the two deterministic classes never reach here:
:integrity— isolated by the Pipeline's per-event fallback and dead-lettered, so the projection keeps moving.:structural— halts the projection loudly via[:scriba, :projection, :halted]; the source is told not to restart.
A restart loop against a genuinely unavailable database is therefore the correct observable behaviour for what remains. A silent stall is not, and neither is an infinite loop against a bad column name.
Verification status (v0.1)
This mechanism — refuse to ack, kill the producer, rewind the subscription, back off, replay — is covered by unit tests only. It has never been exercised against a real event store.
Scriba's own test double, Scriba.Test.Source, discards failed messages
instead of redelivering them, so the suite cannot replay anything and cannot
close the conservation identity across an outage. Measuring it requires a
persistent event store. Treat the paragraphs above as the design, not as
observed behaviour.