Why is MySQL Crashing with \'InnoDB: mmap failed; errno 12\' on my Amazon EC2 Micro Instance?

MySQL Crashes with "InnoDB: mmap failed; errno 12" on Amazon EC2 Micro Instance

An error occurs when MySQL attempts to initialize its buffer pool and encounters a memory allocation failure due to insufficient resources. This issue is prevalent on Amazon EC2 micro instances, which have limited memory capacity (613MB).

Error Message:

InnoDB: mmap(549453824 bytes) failed; errno 12
InnoDB: Completed initialization of buffer pool
InnoDB: Fatal error: cannot allocate memory for the buffer pool
[ERROR] Plugin 'InnoDB' init function returned error.
[ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
[ERROR] Unknown/unsupported storage engine: InnoDB
[ERROR] Aborting

Causes:

• Insufficient memory: MySQL's buffer pool size (512MB) exceeds the available memory on the micro instance.
• No swap space: Micro instances do not have swap space enabled by default, which is needed to expand virtual memory.

Resolution:

1. Enable Swap Space:

• Create a swap file using dd if=/dev/zero of=/swapfile bs=1M count=1024.
• Set up the swap space using mkswap /swapfile.
• Enable the swap file using swapon /swapfile.
• Make the swap file permanent by adding /swapfile swap swap defaults 0 0 to /etc/fstab.

2. Increase Memory Capacity:

• Consider upgrading to a larger instance type with more memory or utilizing Amazon RDS.

3. Check MySQL Memory Settings:

• Ensure that MySQL's memory variables (e.g., innodb_buffer_pool_size) are set appropriately for the available resources.

4. Reduce MySQL Load:

• Optimize MySQL queries to reduce resource consumption.
• Consider using caching mechanisms to minimize database load.

Example my.cnf Configuration:

[mysqld]
innodb_buffer_pool_size = 256M  # Adjust based on available memory

By implementing these steps, you can resolve the "InnoDB: mmap failed; errno 12" error and ensure that MySQL runs smoothly on your Amazon EC2 micro instance.

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