Memcached SERVER_ERROR object too large for cache

What is Memcached SERVER_ERROR object too large for cache

Understanding Memcached

Memcached is a high-performance, distributed memory object caching system, primarily used to speed up dynamic web applications by alleviating database load. It stores data in memory for quick retrieval, making it an essential tool for applications requiring fast data access.

Identifying the Symptom

When using Memcached, you might encounter the error message: SERVER_ERROR object too large for cache. This indicates that an attempt to store an object in the cache has failed because the object exceeds the size limit.

What You Observe

During operations, you may notice that certain data is not being cached as expected. Upon further inspection, the error message appears, signaling that the object size is the issue.

Explaining the Issue

The error SERVER_ERROR object too large for cache occurs when the size of the object you are trying to store in Memcached exceeds the default maximum size limit of 1MB. Memcached has a default item size limit to ensure efficient memory usage and performance.

Why It Happens

This limitation is in place to prevent any single item from consuming too much memory, which could degrade the performance of the cache. If an object is too large, Memcached will not store it, resulting in the error.

Steps to Fix the Issue

To resolve this issue, you can either ensure that the object size is within the allowable limit or adjust the configuration to accommodate larger objects.

Option 1: Reduce Object Size

Review the data structure of the object you are trying to cache. Consider compressing the data before caching it. Libraries like zlib can be used for compression. Break down large objects into smaller chunks and store them separately.

Option 2: Increase Memcached Limit

Modify the Memcached configuration to increase the maximum item size. This can be done by setting the -I option when starting Memcached. For example, to increase the limit to 2MB, use:

memcached -I 2m

Ensure that your server has enough memory to handle larger items without affecting performance. Restart Memcached to apply the changes.

Additional Resources

For more information on Memcached configuration and best practices, consider visiting the official Memcached website or the Memcached GitHub Wiki.

By understanding and addressing the size limitations of Memcached, you can ensure efficient caching and optimal performance for your applications.