MySQL aborts a statement because it waited longer than lock_wait_timeout for an internal metadata or row lock.
ER_LOCKING_SERVICE_TIMEOUT means MySQL killed your statement after waiting past lock_wait_timeout for a lock on a table, row, or metadata object. Find and end the blocking transaction or raise lock_wait_timeout to clear the error.
ER_LOCKING_SERVICE_TIMEOUT
MySQL raises ER_LOCKING_SERVICE_TIMEOUT when a session cannot obtain a service or metadata lock within the period defined by lock_wait_timeout (or metadata_lock_timeout). The server cancels the waiting statement to protect overall throughput.
The error appears from version 5.7.8 onward, mainly for InnoDB tables, but any storage engine that uses metadata locks can trigger it. Correcting the underlying lock contention quickly restores normal operation.
The error surfaces during DDL or long-running DML that requests locks already held by another transaction. Typical moments are ALTER TABLE, CREATE INDEX, or bulk UPDATE statements running in parallel with longer open transactions.
High-traffic OLTP systems with insufficient commit discipline or large interactive sessions often experience this timeout. The issue is critical because it causes statement rollback and lost work.
Most cases involve a blocking transaction that holds metadata locks longer than the configured timeout. Long idle transactions in autocommit=0 mode and open MySQL client sessions are frequent offenders.
Heavy concurrency can saturate the metadata locking subsystem, making ordinary operations like SELECT ... FOR UPDATE wait until the timeout expires.
First, locate the blocker by inspecting performance_schema tables or SHOW PROCESSLIST. Then commit or kill the blocking session to free the lock.
If the blocking workload is legitimate, temporarily raise lock_wait_timeout or metadata_lock_timeout to give operations more time. After clearing the backlog, revert to a safer value.
Scenario: An ALTER TABLE on users stalls because a report connection has an open SELECT transaction. Solution: Close or commit the report session and rerun ALTER TABLE.
Scenario: Bulk UPDATE times out in a high-load API cluster. Solution: Break the update into smaller batches or schedule it during off-peak hours to reduce lock contention.
Keep transactions short and commit promptly. Avoid leaving sessions idle while a transaction is open, especially in GUI clients.
Monitor performance_schema.metadata_locks and information_schema.innodb_trx for growing queues. Set alerts when waits approach the timeout threshold.
Galaxy shows lock-related waits inline in its query output, helping engineers identify blocking sessions fast. You can share the diagnostic query in a Galaxy Collection so team-mates can run it without extra setup.
Interactive sessions or background jobs that keep a transaction open hold metadata and row locks for extended periods.
Running ALTER TABLE or CREATE INDEX while heavy OLTP traffic is active forces metadata locks to queue up.
Very low lock_wait_timeout or metadata_lock_timeout values let ordinary waits trigger the error unnecessarily.
Although not a true deadlock, circular waits among large batches can exhaust the timeout and raise ER_LOCKING_SERVICE_TIMEOUT.
Raised when InnoDB row locks cannot be acquired within innodb_lock_wait_timeout.
Indicates a true deadlock; MySQL rolls back one victim to resolve the cycle.
Occurs when metadata lock acquire exceeds metadata_lock_timeout in newer MySQL versions.
Yes, the statement that timed out is rolled back. If it was part of a multi-statement transaction, only that statement fails, but subsequent statements cannot proceed until you handle the error or end the transaction.
Raising the timeout buys time for maintenance jobs but can delay detection of real blocking issues. Increase only temporarily and monitor lock waits.
Create a scheduled query on performance_schema.metadata_locks in Galaxy and set an alert when the count exceeds a safe threshold.
Restarting clears all locks but causes downtime. It should be a last resort after identifying and fixing the root cause.
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