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Amazon ElastiCache
User Guide (API Version 2015-02-02)

Comparing Memcached Versions

ElastiCache supports these versions of Memcached:

Upgrading to a Newer Version

To upgrade to a newer Memcached version, modify your cache cluster specifying the new engine version you want to use. Upgrading to a newer Memcached version is a destructive process – you lose your data and start with a cold cache. For more information, see Modifying an ElastiCache Cluster.

You should be aware of the following requirements when upgrading from an older version of Memcached to Memcached version 1.4.33 or newer. CreateCacheCluster and ModifyCacheCluster will fail under the following conditions.

  • If slab_chunk_max > max_item_size.

  • If max_item_size modulo slab_chunk_max != 0.

  • If max_item_size > ((max_cache_memory - memcached_connections_overhead) / 4).

    The value (max_cache_memory - memcached_connections_overhead) is the node's memory useable for data. For more information, see Memcached Connection Overhead.

Memcached Version 1.4.34

ElastiCache for Memcached version 1.4.34 adds no new features to version 1.4.33. Version 1.4.34 is a bug fix release that is larger than the usual such release.

For more information, see Memcached 1.4.34 Release Notes at Memcached on github.

Memcached Version 1.4.33

Memcached improvements added since version 1.4.24 include the following:

  • Ability to dump all of the metadata for a particular slab class, a list of slab classes, or all slab classes. For more information, see Memcached 1.4.31 Release Notes.

  • Improved support for large items over the 1 megabyte default. For more information, see Memcached 1.4.29 Release Notes.

  • Ability to specify how long a client can be idle before being asked to close.

    Ability to dynamically increase the amount of memory available to Memcached without having to restart the cluster. For more information, see Memcached 1.4.27 Release Notes.

  • Logging of fetchers, mutations, and evictions are now supported. For more information, see Memcached 1.4.26 Release Notes.

  • Freed memory can be reclaimed back into a global pool and reassigned to new slab classes. For more information, see Memcached 1.4.25 Release Notes.

  • Several bug fixes.

  • Some new commands and parameters. For a list, see Memcached 1.4.33 Added Parameters.

Memcached Version 1.4.24

Memcached improvements added since version 1.4.14 include the following:

  • Least recently used (LRU) management using a background process.

  • Added the option of using jenkins or murmur3 as your hash algorithm.

  • Some new commands and parameters. For a list, see Memcached 1.4.24 Added Parameters.

  • Several bug fixes.

Memcached Version 1.4.14

Memcached improvements added since version 1.4.5 include the following:

  • Enhanced slab rebalancing capability.

  • Performance and scalability improvement.

  • Introduced the touch command to update the expiration time of an existing item without fetching it.

  • Auto discovery—the ability for client programs to automatically determine all of the cache nodes in a cluster, and to initiate and maintain connections to all of these nodes.

Memcached Version 1.4.5

Memcached version 1.4.5 was the initial engine and version supported by Amazon ElastiCache.