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Lock Wait Timeout Exceeded

A database query waited too long for a lock held by another transaction.

Explanation

Lock wait timeout exceeded occurs when a transaction waits longer than the configured timeout period to acquire a lock held by another transaction. Unlike a deadlock (where both transactions block each other), this is a one-way wait - one transaction is holding a lock and the other is waiting for it. The waiting transaction is rolled back after the timeout. Common causes include long-running transactions, missing indexes causing table-level locks, and high-concurrency scenarios.

Common Causes

  • Long-running transactions holding locks
  • Missing indexes causing table locks
  • High-concurrency write operations
  • Lock escalation from row to table
  • Transaction timeout too short

Solution

Identify and optimize long-running transactions that hold locks too long. Add proper database indexes to reduce lock scope. Use SELECT ... FOR UPDATE sparingly. Implement optimistic locking for high-concurrency scenarios. Increase innodb_lock_wait_timeout in MySQL if appropriate (default is 50 seconds). Monitor active transactions with SHOW ENGINE INNODB STATUS. Break large transactions into smaller ones. Use queue-based processing for write-heavy operations.

Code Example 

// Long transaction holding a lock
DB::beginTransaction();
User::where('id', 1)->update(['status' => 'active']);
// ... long processing ...
// Another query tries to update same row - TIMEOUT!
DB::commit();

// Fix: keep transactions short
DB::beginTransaction();
User::where('id', 1)->update(['status' => 'active']);
DB::commit(); // commit immediately

// Monitor locks in MySQL
SHOW ENGINE INNODB STATUS;
SELECT * FROM information_schema.innodb_locks;
SELECT * FROM information_schema.innodb_trx;

// Increase timeout (MySQL)
SET GLOBAL innodb_lock_wait_timeout = 120;
// Or in my.cnf: innodb_lock_wait_timeout = 120

// Use optimistic locking in Eloquent
class User extends Model
{
    use OptimisticLocking;
    // Adds 'version' column for conflict detection
}

Error Information

Language

php

Difficulty

Advanced

Views

195

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