Configuring WAN Replication

WAN replication allows you to keep Hazelcast clusters in sync across multiple sites or cloud deployments. In Hazelcast Platform Operator, you can create a WanReplication resource to replicate multiple maps from multiple source clusters to a single target Hazelcast cluster.

See WAN replication for more detailed information about the configuration and behavior of WAN replication in Hazelcast.

Prerequisites for WAN Replication

Before you create and configure a WanReplication resource, you need to create the following:

At least one Hazelcast resource and one Map resource for the source Hazelcast cluster.
A target Hazelcast cluster that is accessible from the source cluster.

Configuring the WanReplication Resource

You can use the following configuration options in your WanReplication resource. For more detailed information, see the API Reference.

Field Description

Field	Description
`resources`	The list of custom `Map` or `Hazelcast` resources to which WAN replication applies. `name`: The name of custom resource to which WAN replication applies. `kind`: The type of custom resource. Either `Map`(default) or `Hazelcast`. Use the `Hazelcast` kind to apply WAN replication to all custom maps created under the given `Hazelcast` resource. Wan Replication will be started automatically for newly created Map resources as well.
`targetClusterName`	The name of the Hazelcast cluster that is the target of replication.
`endpoints`	A comma-separated list of the addresses of the Hazelcast members in the target cluster.
`queue`	The configuration of the WAN events queue, which includes two related parameters: `capacity`: The total capacity of WAN events queue. The `fullBehavior` is triggered when the number of events exceeds this limit. `fullBehavior`: What happens to new events that arrive after the events queue is full.
`batch`	How WAN replication events are batched. `size`: The maximum batch size. `maximumDelay`: If the batch size is not reached, the events will be sent after the maximum delay (in milliseconds).
`acknowledgement`	Configuration of the acknowledgement sent after a batch of replication events is received by the target cluster: `type`: Whether an acknowledgement is sent as soon as the batch of events is received (`ACK_ON_RECEIPT`) or after each update is applied to the target cluster (`ACK_ON_OPERATION_COMPLETE`). `timeout`: The period of time the source cluster waits for the acknowledgement. If the confirmation is not received before the timeout, the replication events are resent.

resources

The list of custom Map or Hazelcast resources to which WAN replication applies.

name: The name of custom resource to which WAN replication applies.
kind: The type of custom resource. Either Map(default) or Hazelcast. Use the Hazelcast kind to apply WAN replication to all custom maps created under the given Hazelcast resource. Wan Replication will be started automatically for newly created Map resources as well.

targetClusterName

The name of the Hazelcast cluster that is the target of replication.

endpoints

A comma-separated list of the addresses of the Hazelcast members in the target cluster.

queue

The configuration of the WAN events queue, which includes two related parameters:

capacity: The total capacity of WAN events queue. The fullBehavior is triggered when the number of events exceeds this limit.
fullBehavior: What happens to new events that arrive after the events queue is full.

batch

How WAN replication events are batched.

size: The maximum batch size.
maximumDelay: If the batch size is not reached, the events will be sent after the maximum delay (in milliseconds).

acknowledgement

Configuration of the acknowledgement sent after a batch of replication events is received by the target cluster:

type: Whether an acknowledgement is sent as soon as the batch of events is received (ACK_ON_RECEIPT) or after each update is applied to the target cluster (ACK_ON_OPERATION_COMPLETE).
timeout: The period of time the source cluster waits for the acknowledgement. If the confirmation is not received before the timeout, the replication events are resent.

Example Configuration

The following WanReplication resource creates the WAN replication configuration for the Hazelcast and Map resources on the source Hazelcast cluster.

Example configuration

apiVersion: hazelcast.com/v1alpha1
kind: WanReplication
metadata:
  name: wanreplication-sample
spec:
  resources:
    - name: map-sample
      kind: Map
    - name: hz-sample
      kind: Hazelcast
  targetClusterName: dev
  endpoints: "35.192.33.252,35.192.33.255"
  queue:
    capacity: 10000
    fullBehavior: DISCARD_AFTER_MUTATION
  batch:
    size: 500
    maximumDelay: 1000
  acknowledgement:
    type: ACK_ON_OPERATION_COMPLETE
    timeout: 60000

If port number is not specified in the endpoints, the default Hazelcast port '5710' is joined to the endpoints.

Checking the Status of a WAN Replication

After creating the WanReplication resource, run the following command to find out the WAN replication status:

kubectl get wanreplication wanreplication-sample -o wide

The returned status message will look something like this:

NAME                     STATUS    MESSAGE
wanreplication-sample    Success

You can also monitor the status of WAN replications in Management Center.

Deleting the WanReplication Custom Resource

Deleting the WanReplication object stops the replication of all maps in the .spec.resources field and clears the queues.