Capturing a Cluster Snapshot

Before you begin

Warning: Improperly configuring Memory Machine or Hazelcast can make it impossible to restore a Hazelcast cluster. Always test cluster snapshot create and cluster snapshot restore with your configuration before applying your configuration in production.

About this task

Warning:

Replacing a certificate will cause restore of existing cluster snapshots to fail.

If you create a Hazelcast cluster with TLS using a certificate, then replace the certificate in the Hazelcast cluster and on the coordinators, any snapshots you take before replacing the certificate cannot be restored. This is expected behavior; a snapshot should be restored only under the certificate it was captured with. Plan accordingly.

Important: When capturing a cluster snapshot, the Hazelcast cluster and all Hazelcast members must be in the Active state. When capturing a cluster snapshot, Memory Machine temporarily changes the Hazelcast cluster to the Passive state for the duration of the capture process. Once the cluster snapshot is captured, Memory Machine changes the Hazelcast cluster back to the Active state.

Important: Cluster snapshot does not support tmux. You cannot restore a TTY session from a cluster snapshot. See Restoring a TTY Session for information about restoring a TTY session from an individual snapshot.

Procedure

On the Primary Coordinator host, issue the following command to capture a snapshot of the registered Hazelcast cluster.
```
mvmcli cluster snapcreate --name=cluster_name --label=snap_label
```
where:

cluster_name

is the name under which you registered the cluster. See Preparing Hazelcast to Work with Memory Machine.

snap_label

is a base name that you assign to the label of the snapshot.
If the command fails, check the error log to determine the cause of the failure.
```
# cd /var/log/memverge
# less mvcsnapd_log
```

If the command was successful, use the mvmcli cluster list command to verify that the cluster snapshot was captured and to display the Hazelcast member snapshots. For example:

# mvmcli cluster list --members
Name                Profile     Cluster Contact Member   Create Time
---------------------------------------------------------------------------------
---------------------
hz-cluster-1        hazelcast   10.0.0.63:5701           Tue Dec  1 16:09:15 2020
Snapshots:               Status         Label               Create Time
                                        hz1-snap01          Tue Dec  1 16:32:05 2020
                           Members:
                           Address               Coordinator           Label
                           10.0.0.62:5701        10.0.0.62:5679        hz1-snap01_75099ae5
                           10.0.0.62:5702        10.0.0.62:5679        hz1-snap01_2b7e554d
                           10.0.0.63:5701        10.0.0.63:5679        hz1-snap01_c89cd515
                           10.0.0.63:5702        10.0.0.63:5679        hz1-snap01_5abfa3c1

To see the cluster snapshot without the member snapshot list, omit the --members option.