The list of Availability Zones where the new Memcached cache nodes will be created.
This parameter is only valid when NumCacheNodes in the request is greater than the sum of the number of active cache nodes and the number of cache nodes pending creation (which may be zero). The number of Availability Zones supplied in this list must match the cache nodes being added in this request.
This option is only supported on Memcached clusters.
Scenario 1: You have 3 active nodes and wish to add 2 nodes. Specify
NumCacheNodes=5 (3 + 2) and optionally specify two Availability Zones for the two new nodes.
Scenario 2: You have 3 active nodes and 2 nodes pending creation (from
the scenario 1 call) and want to add 1 more node. Specify NumCacheNodes=6 ((3 + 2) + 1) and optionally specify an Availability Zone for the new node.
Scenario 3: You want to cancel all pending actions. Specify NumCacheNodes=3
to cancel all pending actions.
The Availability Zone placement of nodes pending creation cannot be modified.
If you wish to cancel any nodes pending creation, add 0 nodes by setting NumCacheNodes to the number of current nodes.
If cross-az is specified, existing Memcached nodes remain in their current Availability Zone. Only newly created nodes can be located in different Availability Zones. For guidance on how to move existing Memcached nodes to different Availability Zones, see the Availability Zone Considerations section of Cache Node Considerations for Memcached (http://docs.aws.amazon.com/AmazonElastiCache/latest/UserGuide/CacheNode.Memcached.html).
Impact of new add/remove requests upon pending requests Scenario-1 Pending Action: Delete New Request: Delete Result: The new delete, pending or immediate, replaces the pending delete. Scenario-2 Pending Action: Delete New Request: Create Result: The new create, pending or immediate, replaces the pending delete. Scenario-3 Pending Action: Create New Request: Delete Result: The new delete, pending or immediate, replaces the pending create. Scenario-4 Pending Action: Create New Request: Create Result: The new create is added to the pending create. Important: If the new create request is Apply Immediately - Yes, all creates
are performed immediately. If the new create request is Apply Immediately - No, all creates are pending.