MySQL service crashes are usually caused by insufficient resources, configuration errors, hardware problems or software conflicts, and the troubleshooting needs to be carried out in steps. 1. First check the MySQL error log to find warnings or error messages before crashes, such as insufficient memory, table space loss, etc., and it is recommended to monitor the log regularly. 2. Check the use of system resources, including memory, CPU and disk space. It is recommended to use monitoring tools and reasonably set the InnoDB buffer pool size. 3. Check the rationality of MySQL configuration, such as the maximum number of connections, log file size and other parameters. It is recommended to use MySQL Tuner to analyze and back up the configuration file before modifying it. 4. Troubleshoot hardware or system problems, such as hard disk failure, system update impact, permission restrictions, etc. It is recommended to view the system log and I/O status. 5. Check for external software interference, such as antivirus software, timing tasks or unstable plug-ins. It is recommended to close irrelevant programs and review script operations. During the troubleshooting, logging, then resource, configuration, and system should be first, and then external interference should be gradually located.

MySQL service crash problems are actually quite common, especially when the load is high or the configuration is improper. To put it directly, the key point: Crash is usually caused by insufficient resources, configuration errors, hardware problems, or software conflicts . When troubleshooting, you should start with the log and analyze it step by step in combination with the system status.

1. Check the MySQL error log

When there is a problem with MySQL, the first reaction should be to look at the error log. It usually records warnings or error messages before crashes, such as:

• Out of memory
• InnoDB: Assertion failure
• Tablespace is missing
• Access denied for user

Log locations can be viewed via SHOW VARIABLES LIKE 'log_error'; ;.

suggestion:

• Check the logs regularly and don't wait until the service is out before fetching.
• In conjunction with tail -f /path/to/error.log , monitor the startup process in real time.
• If Deadlock found frequently appears in the log, it means there is a transaction conflict and it may be necessary to optimize SQL or transaction design.

2. Check the use of system resources

MySQL crashes often because the system resources cannot hold on, such as:

• Out of memory (OOM) : Especially when the InnoDB buffer pool (innodb_buffer_pool_size) is used too large.
• CPU load too high : Long-term full load operation may cause slow response or even crash.
• Insufficient disk space : Unable to write logs, temporary files, or data files can also trigger a crash.

suggestion:

• Use top , htop , free -m , df -h and other commands to view the real-time status.
• It is safe to adjust innodb_buffer_pool_size in the configuration file, generally set it to 50%~70% of physical memory.
• Set up monitoring alarms, such as using Prometheus Grafana or Zabbix.

3. Check whether the MySQL configuration is reasonable

Many crashes are caused by unreasonable configurations, such as:

• max_connections set too high, resulting in excessive connections and exhaustion of resources.
• innodb_log_file_size is too small, frequent log writing affects performance.
• The appropriate tmp_table_size and max_allowed_packet are not set, causing the query to fail or crash.

suggestion:

• Use MySQL Tuner ( mysqltuner.pl ) to do a preliminary analysis to see which parameters may be problematic.
• Remember to restart the service after each configuration change and observe whether there are any abnormalities in the log.
• If you are not sure, you can back up the configuration file first and then modify it to facilitate rollback.

4. Check for hardware or system problems

Sometimes the problem is not MySQL itself, but at the system level:

• Hard disk failure : Data file corruption will cause startup failure.
• System updates or kernel upgrades : Sometimes it causes compatibility issues.
• SELinux or AppArmor permission restriction : prevents MySQL from running properly.

suggestion:

• Use dmesg | grep -i kill to see if the system is killed because OOM.
• Check the system logs by looking at /var/log/messages or journalctl .
• If it is a virtual machine or cloud server, check whether the disk I/O is abnormal.

5. Check for external software conflicts

Some security software, backup tools, or scripts may interfere with the operation of MySQL, such as:

• Antivirus software scans the data directory, causing the file to be locked.
• The timing task is performed improperly , such as using kill -9 to force MySQL to end.
• Third-party plug-ins or storage engines are unstable.

suggestion:

• Close unnecessary third-party software, especially those with access to data directories.
• Check if there is a timed script in crontab to operate MySQL.
• If it is a plug-in problem, try disabling and restarting the service to observe.

Basically these common reasons. When troubleshooting, take it step by step, first look at the logs, then look at the resources, then look at the configuration and system, and finally consider external interference. Not complicated but it is easy to ignore details.

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