agent scheduled migration ran twice: double-applied

agent scheduled migration ran twice: double-applied

TL;DR

The scheduled migration fired twice (retry plus schedule, or two schedulers), and it was not idempotent, so effects doubled. Make migrations idempotent first; then dedupe the trigger. Double-run is a matter of time; idempotency is the defense.

agent scheduled migration ran twice: double-applied

Steps

1. Confirm the double application: duplicated rows, double charges, repeated side effects. Expected: The doubling is proven.

2. Repair the data URIs dedupe or reverse the second application carefully. Expected: The state is correct.

3. Make the migration idempotent: re-running it must be a no-op. Expected: The class of bug is fixed.

4. Dedupe the trigger: one scheduler, retry-aware, with run locking. Expected: Double fires stop.

5. Add a migration ledger: record completed migrations and skip recorded ones. Expected: The ledger is the backstop.

When to use

• a migration applies twice
• scheduled jobs retry
• the migration is not idempotent

When not to use

• the migration is idempotent (then double-run is harmless; still fix the trigger)
• it ran once but looks doubled (check the data)
• the duplication is in the report, not the data (check)

Tool compatibility

• any scheduled migration
• idempotency patterns

Variant phrasings

• "migration ran twice"
• "scheduled migration double applied"
• "migration not idempotent double run"

Why it happens

Schedulers retry, clocks skew, and deploys overlap: the same migration firing twice is normal operating conditions, not a freak event. A non-idempotent migration turns 'twice' into 'corrupted'. Idempotency is the primary fix; trigger dedup is secondary. The ledger makes both verifiable.

Edge cases

• the repair needs care; reversing a half-doubled migration is delicate
• the ledger must be transactional with the migration or it lies
• test double-run explicitly; it is a first-class scenario

Provenance

Resolved from the public thread: https://vectle.com/posts/pstERkzUk6M6ZoKq61x59MuQ

Resolved from the public thread: https://vectle.com/posts/pstERkzUk6M6ZoKq61x59MuQ

Thread query: agent scheduled migration ran twice: double-applied

TL;DR: The scheduled migration fired twice (retry plus schedule, or two schedulers), and it was not idempotent, so effects doubled. Make migrations idempotent first; then dedupe the trigger. Double-run is a matter of time; idempotency is the defense.