A nonstop cache allows certain cache operations to proceed on clients that have become disconnected from the cluster, or if a cache operation cannot complete by the nonstop timeout value. This is useful in meeting service-level agreement (SLA) requirements, responding to node failures, and building a more robust High Availability cluster.
One way clients go into nonstop mode is when they receive a “cluster offline” event. Note that a nonstop cache can go into nonstop mode even if the node is not disconnected, such as when a cache operation is unable to complete within the timeout allotted by the nonstop configuration.
Nonstop can be used in conjunction with rejoin.
Use cases include:
Setting timeouts on cache operations.
For example, say you use the cache rather than a mainframe. The SLA calls for 3 seconds. There is a temporary network interruption that delays the response to a cache request. With the timeout you can return after 3 seconds. The lookup is then done against the mainframe. This could also be useful for write-through, writes to disk, or synchronous writes.
Automatically responding to cluster topology events to take a pre-configured action.
Allowing Availability over Consistency within the CAP theorem when a network partition occurs.
Providing graceful degradation to user applications when Distributed Cache becomes unavailable.
Nonstop caches are available with BigMemory Max.