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You can control if and when the protocol-compliant software powering your cache cluster is upgraded to new versions that are supported by ElastiCache. This enables you to maintain compatibility with specific Memcached or Redis versions, test new versions with your application before deploying in production, and perform version upgrades on your own terms and timelines.
Since major version upgrades involve some compatibility risk, they will not occur automatically and must be initiated by you. Automatic patching works only for minor upgrades; for example, from Memcached 1.4.5 to 1.4.6, or from Redis 2.6.10 to 2.6.13. Automatic patching will not work for major upgrades (for example, from Memcached version 1.4.x to 1.5.x, or from Redis 2.6.x to 2.8.x). You can manually initiate major version upgrades to your cache cluster by modifying the cache cluster and specifying a new engine version.
While cache engine version management functionality is intended to give you as much control as possible over how patching occurs, ElastiCache reserves the right to patch your cache cluster on your behalf in the event of a critical security vulnerability in the system or cache software.
Automatic patching will occur during the scheduled maintenance window for your cache clusters, and will be announced on the ElastiCache discussion forum in advance. Automatic version upgrades are enabled by default on new cache clusters; if you wish to turn off automatic version upgrades, you can do so by selecting the “Auto Minor Version Upgrade” for your cache cluster to “No”.
Every cache cluster has a weekly maintenance window during which any system changes are applied. If you don't specify a preferred maintenance window when you create the cache cluster, ElastiCache assigns a 60-minute maintenance window on a randomly selected day of the week.
The 60-minute maintenance window is selected at random from an 8-hour block of time per region. The following table lists the time blocks for each region from which the default maintenance windows are assigned.
|US East (Northern Virginia) Region||03:00-11:00 UTC|
|US West (Northern California) Region||06:00-14:00 UTC|
|US West (Oregon) Region||06:00-14:00 UTC|
|EU (Ireland) Region||22:00-06:00 UTC|
|Asia Pacific (Singapore) Region||14:00-22:00 UTC|
|Asia Pacific (Sydney) Region||01:00-09:00 UTC|
|Asia Pacific (Tokyo) Region||17:00-03:00 UTC|
|South America (Sao Paulo) Region||01:00-09:00 UTC|
The maintenance window should fall at the time of lowest usage and thus might need modification from time to time. You can specify a time range of up to 24 hours in duration during which any maintenance activities you have requested should occur. For example, if you enable Auto Minor Version Upgrades for your cache cluster, non-critical Memcached or Redis software updates are applied during this time. Such updates occur infrequently (generally once every few months) and will be announced on the AWS ElastiCache forum two weeks prior to being applied. Any deferred or pending cache cluster modifications you have requested would also occur during this time.
For more information on how to adjust the preferred maintenance window for your cache clusters, see Adjusting the Preferred Maintenance Window.