Can we change Hazelcast MapConfig after Map initialization

[Nitin Singh]

We can specify MapConfig from either static cluster-config.xml files or programmatically from code. While creating IMap instance from code,

1) Is it possible to change mapConfig after map initialization has been done.

2) Will such changes for example - backup count or max size reflect live on already partitioned map across nodes (leading to eviction of entries or creation of more backups). If this does not happen by default, will it be picked up on some next event threshold or can we trigger the new config changes to apply programmatically ?

Sample code

HazelcastInstance hazelcastInstance = Hazelcast.getHazelcastInstanceByName(instanceName);

Config config = hazelcastInstance.getConfig();
config.getMapConfig(name)
.setBackupCount(computedBackupCount)
.setMaxSizePolicy(MaxSizePolicy.PER_NODE).setSize(computedSize);

[Jiri Holusa]

Hi Nitin,

sorry for a very late response, the email kind of slipped through my radar.

You can't change an existing map. You can only add new: https://docs.hazelcast.com/hazelcast/5.1-snapshot/configuration/dynamic-data-structure-configuration

Hope this helps,

Jiri

[Nitin Singh]

Thank you for the confirmation

[Bence Eros]

Hello Nitin,

there is support in Hazelcast Management Center for updating a couple of fields of the map configuration: https://docs.hazelcast.com/management-center/5.0/data-structures/map#map-config

In case it fits your needs, please keep in mind that these changes are not persisted anywhere, so if you restart a cluster member then your changes will be gone.

Kind regards,

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Bence Erős

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