Charmed OpenSearch Tutorial > 6. Scale horizontally
Scale Charmed OpenSearch horizontally
After having indexed some data in our previous section, let’s take a look at the status of our charm:
juju status
The output should look similar to the following:
Model Controller Cloud/Region Version SLA Timestamp
tutorial opensearch-demo localhost/localhost 3.5.3 unsupported 13:57:38Z
App Version Status Scale Charm Channel Rev Exposed Message
data-integrator active 1 data-integrator latest/edge 59 no
opensearch active 3 opensearch 2/beta 117 no
self-signed-certificates active 1 self-signed-certificates latest/stable 155 no
Unit Workload Agent Machine Public address Ports Message
data-integrator/0* active idle 4 10.95.38.22
opensearch/0* active idle 0 10.95.38.94 9200/tcp
opensearch/1 active idle 1 10.95.38.139 9200/tcp
opensearch/2 active idle 2 10.95.38.212 9200/tcp
self-signed-certificates/0* active idle 3 10.95.38.54
Machine State Address Inst id Base AZ Message
0 started 10.95.38.94 juju-be3883-0 ubuntu@22.04 Running
1 started 10.95.38.139 juju-be3883-1 ubuntu@22.04 Running
2 started 10.95.38.212 juju-be3883-2 ubuntu@22.04 Running
3 started 10.95.38.54 juju-be3883-3 ubuntu@22.04 Running
4 started 10.95.38.22 juju-be3883-4 ubuntu@22.04 Running
Integration provider Requirer Interface Type Message
data-integrator:data-integrator-peers data-integrator:data-integrator-peers data-integrator-peers peer
opensearch:node-lock-fallback opensearch:node-lock-fallback node_lock_fallback peer
opensearch:opensearch-client data-integrator:opensearch opensearch_client regular
opensearch:opensearch-peers opensearch:opensearch-peers opensearch_peers peer
opensearch:upgrade-version-a opensearch:upgrade-version-a upgrade peer
self-signed-certificates:certificates opensearch:certificates tls-certificates regular
Add node
You can add two additional nodes to your deployed OpenSearch application with the following command:
juju add-unit opensearch -n 1
Where -n 1 specifies the number of units to add. In this case, we are adding one unit to the OpenSearch application. You can add more units by changing the number after -n.
You can now watch the new units join the cluster with: juju status --watch 1s. It usually takes a few minutes for the new nodes to be added to the cluster formation. You’ll know that all three nodes are ready when juju status --watch 1s reports:
Model Controller Cloud/Region Version SLA Timestamp
tutorial opensearch-demo localhost/localhost 3.5.3 unsupported 14:02:18Z
App Version Status Scale Charm Channel Rev Exposed Message
data-integrator active 1 data-integrator latest/edge 59 no
opensearch active 4 opensearch 2/beta 117 no
self-signed-certificates active 1 self-signed-certificates latest/stable 155 no
Unit Workload Agent Machine Public address Ports Message
data-integrator/0* active idle 4 10.95.38.22
opensearch/0* active idle 0 10.95.38.94 9200/tcp
opensearch/1 active idle 1 10.95.38.139 9200/tcp
opensearch/2 active idle 2 10.95.38.212 9200/tcp
opensearch/3 active idle 5 10.95.38.39 9200/tcp
self-signed-certificates/0* active idle 3 10.95.38.54
Machine State Address Inst id Base AZ Message
0 started 10.95.38.94 juju-be3883-0 ubuntu@22.04 Running
1 started 10.95.38.139 juju-be3883-1 ubuntu@22.04 Running
2 started 10.95.38.212 juju-be3883-2 ubuntu@22.04 Running
3 started 10.95.38.54 juju-be3883-3 ubuntu@22.04 Running
4 started 10.95.38.22 juju-be3883-4 ubuntu@22.04 Running
5 started 10.95.38.39 juju-be3883-5 ubuntu@22.04 Running
You can trust that Charmed OpenSearch added these nodes correctly, and that your replica shards are all assigned. But if you want to verify that your data is correctly replicated, you can also query the shards with the following command:
curl --cacert demo-ca.pem -XGET https://username:password@opensearch_node_ip:9200/_cat/shards
Which should result in the following output:
test-index 0 r STARTED 0 208b 10.95.38.94 opensearch-0.0f3
test-index 0 p STARTED 0 208b 10.95.38.139 opensearch-1.0f3
.plugins-ml-config 0 r STARTED 1 3.9kb 10.95.38.94 opensearch-0.0f3
.plugins-ml-config 0 r STARTED 1 3.9kb 10.95.38.139 opensearch-1.0f3
.plugins-ml-config 0 p STARTED 1 3.9kb 10.95.38.212 opensearch-2.0f3
.opensearch-observability 0 r STARTED 0 208b 10.95.38.94 opensearch-0.0f3
.opensearch-observability 0 p STARTED 0 208b 10.95.38.139 opensearch-1.0f3
.opensearch-observability 0 r STARTED 0 208b 10.95.38.212 opensearch-2.0f3
albums 0 r STARTED 4 10.7kb 10.95.38.139 opensearch-1.0f3
albums 0 p STARTED 4 10.7kb 10.95.38.212 opensearch-2.0f3
.opensearch-sap-log-types-config 0 r STARTED 10.95.38.94 opensearch-0.0f3
.opensearch-sap-log-types-config 0 r STARTED 10.95.38.139 opensearch-1.0f3
.opensearch-sap-log-types-config 0 p STARTED 10.95.38.212 opensearch-2.0f3
.opendistro_security 0 r STARTED 10 54.2kb 10.95.38.94 opensearch-0.0f3
.opendistro_security 0 r STARTED 10 54.2kb 10.95.38.139 opensearch-1.0f3
.opendistro_security 0 p STARTED 10 155.1kb 10.95.38.212 opensearch-2.0f3
.charm_node_lock 0 r STARTED 1 3.8kb 10.95.38.94 opensearch-0.0f3
.charm_node_lock 0 r STARTED 1 6.9kb 10.95.38.139 opensearch-1.0f3
.charm_node_lock 0 p STARTED 1 11.8kb 10.95.38.212 opensearch-2.0f3
Notice that the shards are distributed across all nodes.
Remove nodes
Note: Refer to safe-horizontal-scaling guide to understand how to safely remove units in a production environment.
Warning: In highly available deployment, only scaling down to 3 nodes is safe. If only 2 nodes are online, neither can be unavailable nor removed. The service will become unavailable and data may be lost if scaling below 2 nodes.
Removing a unit from the Juju application scales down your OpenSearch cluster by one node. Before we scale down the nodes we no longer need, list all the units with juju status. Here you will see four units / nodes: opensearch/0, opensearch/1, opensearch/2, opensearch/3. To remove the unit opensearch/3 run:
juju remove-unit opensearch/3
You’ll know that the node was successfully removed when juju status --watch 1s reports:
Model Controller Cloud/Region Version SLA Timestamp
tutorial opensearch-demo localhost/localhost 3.5.3 unsupported 14:05:58Z
App Version Status Scale Charm Channel Rev Exposed Message
data-integrator active 1 data-integrator latest/edge 59 no
opensearch active 3 opensearch 2/beta 117 no
self-signed-certificates active 1 self-signed-certificates latest/stable 155 no
Unit Workload Agent Machine Public address Ports Message
data-integrator/0* active idle 4 10.95.38.22
opensearch/0* active idle 0 10.95.38.94 9200/tcp
opensearch/1 active idle 1 10.95.38.139 9200/tcp
opensearch/2 active idle 2 10.95.38.212 9200/tcp
self-signed-certificates/0* active idle 3 10.95.38.54
Machine State Address Inst id Base AZ Message
0 started 10.95.38.94 juju-be3883-0 ubuntu@22.04 Running
1 started 10.95.38.139 juju-be3883-1 ubuntu@22.04 Running
2 started 10.95.38.212 juju-be3883-2 ubuntu@22.04 Running
3 started 10.95.38.54 juju-be3883-3 ubuntu@22.04 Running
4 started 10.95.38.22 juju-be3883-4 ubuntu@22.04 Running
Next step: 7. Clean up the environment.