Database transaction opened without a deferred rollback

Playbook ID: missing-transaction-rollback Category: runtime Severity: high Tags: source, go, database, transaction, sql, reliability

What this failure means

A database transaction is opened and committed in the same function with no defer tx.Rollback() guard, so if an error path returns early the transaction is silently left open, holding connections and locks.

Common log signals

(This playbook uses source-code pattern matching rather than log signals.)

Diagnosis

A db.Begin() or db.BeginTx() call is followed by tx.Commit() in the same function, but there is no defer tx.Rollback() to release the transaction on error paths.

The idiomatic Go pattern defers a rollback immediately after a successful Begin:

tx, err := db.Begin()
if err != nil { return err }
defer tx.Rollback() // safe no-op if Commit already succeeded

Without the deferred rollback:

• Any early return on an error before Commit leaves the transaction open until the database connection times out.
• Under concurrent load, leaked transactions exhaust the connection pool.
• Table locks held by uncommitted transactions block other writers.

Fix steps

1. Add defer tx.Rollback() immediately after a successful Begin:

   tx, err := db.BeginTx(ctx, nil)
   if err != nil {
       return fmt.Errorf("begin tx: %w", err)
   }
   defer tx.Rollback() // always deferred; no-op after a successful Commit
   
   // ... mutations ...
   
   return tx.Commit()
   

2. Return the error from Commit so the caller knows if it failed.
3. Avoid capturing tx in a closure that may outlive the deferred rollback.

Validation

• Run faultline inspect . from the repository root and confirm this source finding is absent or intentionally mitigated.
• Test that an error on any path before Commit releases the connection cleanly without exhausting the pool.

Likely files to inspect

• **/*.go

Run Faultline

faultline analyze build.log
faultline explain missing-transaction-rollback
faultline workflow build.log --json --mode agent

Search phrases this page answers

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• faultline explain missing-transaction-rollback
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Generated from playbooks/bundled/source/missing-transaction-rollback.yaml. Do not edit directly — run make docs-generate.