About Replica error Read Replica Replication Error - SQLError: 1317

Question

Good afternoon.
We have a Mysql 5.7 read replica in the latest update patch that stops replication due to the error below, but I am unable to identify why this happens, considering that in the other replica it is applying correctly and without any errors . Only in 1 replica.

The error:
Read Replica Replication Error - SQLError: 1317, reason: Error 'Query execution was interrupted' on query. Default database: 'checklis_checklist'. Query: 'update `cl_resultado_imagem` set `secundario` = 'p', `cl_resultado_imagem`.`updated_at` = '2023-09-29 13:50:52' where `cl_resultado_imagem`.`id` in (283723161) and `cl_resultado_imagem`.`deleted_at` is null'
September 29, 2023, 10:54 (UTC-03:00)
Replication for the Read Replica resumed

or

sometimes I receive this message:
The slave coordinator and worker threads are stopped, possibly leaving data in inconsistent state. A restart should restore consistency automatically, 
although using non-transactional storage for data or info tables or DDL queries could lead to problems. In such cases you have to examine your data (see documentation for details).

Answer

Hello!

The error `SQLError: 1317` corresponds to "Query execution was interrupted". Here are some potential causes and solutions:

**Causes**:

1. **Manual Interruption**:
   * A long-running query on a replica might have been manually killed, either by a DBA or by some automated process that detected and interrupted long-running queries.
2. **Resource Constraints**:
   * Sometimes, queries can be interrupted if the database server runs into resource constraints, such as memory or CPU bottlenecks.
3. **System Maintenance or Restarts**:
   * System-level operations or restarts could interrupt the ongoing database operations on the replica.
4. **Inconsistent Data or Schema Differences**:
   * Differences in schema or data between master and replica can cause replication errors. Though this usually results in different types of errors, it's always a good area to check.
5. **MySQL Internal Timeout**:
   * MySQL has certain internal timeouts that might interrupt a query if it runs longer than these settings.

**Solutions**:

1. **Monitor Resources**:
   * Keep an eye on the resource utilization of your replica to determine if it's hitting any limits.
2. **Check Logs**:
   * The MySQL error log and the slow query log might give you insights into what caused the interruption.
3. **Consistency**:
   * Ensure both master and replica have consistent data. Tools like `pt-table-checksum` from Percona Toolkit can be helpful.
4. **Adjust Timeouts**:
   * If a query is being interrupted due to an internal timeout, consider adjusting the related MySQL timeout settings. But be careful, as increasing certain timeouts can have side effects.
5. **Restart Replica**:
   * As the error suggests, sometimes a simple restart can help, especially if the replica's internal state is inconsistent.
6. **Examine Data**:
   * For any error that suggests data inconsistency, it's vital to examine and compare data between master and replica to ensure integrity.

Lastly, if you have more than one replica and only one is showing the error, it's possible that there's something unique about the problematic replica, like different configuration, hardware issues, or network problems. It's essential to compare the configurations and status of both the working and non-working replicas to spot any differences.

Hope this helps! Let me know if you have more questions.

About Replica error Read Replica Replication Error - SQLError: 1317

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