Hazelcast dynamic imap configuration propagation to members

Question

If I have multiple Hazelcast cluster members using the same IMap and I want to configure the IMap in a specific manner programmatically, do I then need to have the configuration code in all the members, or should it be enough to have the configuration code just once in one of the members?

In other words, are the MapConfigs only member specific or cluster wide?

Why I'm asking is that Hazelcast documentation http://docs.hazelcast.org/docs/latest/manual/html-single/index.html#configuring-programmatically

says that

As dynamically added data structure configuration is propagated across all cluster members, failures may occur due to conditions such as timeout and network partition. The configuration propagation mechanism internally retries adding the configuration whenever a membership change is detected.

this gives me the impression that the configurations propagate.

Now if member A specifies a certain MapConfig for IMap "testMap", should member B see that config when it does

hzInstance.getConfig.findMapConfig("testMap") #or .getMapConfig("testMap")

In my testing B did not see the MapConfig done by A.

I also tried specifying at A mapConfig.TimeToLiveSeconds(60), and at B mapConfig.TimeToLiveSeconds(10).

It seemed that the items in the IMap that were owned by A were evicted in 60 seconds, while the items owned by B were evicted in 10 seconds. This supports the idea that each member needs to do the same configuration if I want consistent behaviour for the IMap.

Answer 1

Each member owns certain partitions of the IMap. A member's IMap configuration has effect only on its owned partitions. So it is normal to see different TTL values of the entries of the same map in different members when they have different configurations. As you said, all members have should have same IMap configuration to have a cluster-wide persistent behavior. Otherwise, each member will apply its own configuration to its own partitions.

But if add a dynamic configuration as described here, then that configuration is propagated to all members and change their behavior as well.

In brief, if you add the configuration before creating the instance, that is local configuration. But, if you add it after creating the instance, that is dynamic configuration and propagates to all members.