How to perform a minor upgrade

Example: OpenSearch X.Y → OpenSearch X.Y+1

This guide explains how to perform a minor upgrade of the OpenSearch cluster deployed with the Charmed OpenSearch operator. A minor upgrade is an upgrade from one minor version to another, for example, from OpenSearch 2.14 to OpenSearch 2.15.

This guide will walk you through the steps to upgrade your OpenSearch cluster, including pre-upgrade checks, upgrading the OpenSearch cluster, preparing the application for the in-place upgrade, initiating the upgrade, resuming the upgrade, and checking the cluster’s health.

Summary

• Pre-upgrade checks
• Upgrade the OpenSearch cluster
  • Collect all necessary pre-upgrade information
  • Scale-up (optional)
• Prepare the application for the in-place upgrade
• Initiate the upgrade
• Resume upgrade
• Rollback (optional)
• Scale-back (optional)
• Check the cluster health

Pre-upgrade checks

Before upgrading your OpenSearch cluster, ensure that you have completed the following steps:

1. Backup your data: Before upgrading, back up your data to prevent data loss in case of failure. For more information, see Hot to create a backup.
2. Make sure not to perform any extraordinary operations: Avoid performing any concurrent operations on the cluster during the upgrade process. This can lead to an inconsistent state of the cluster. This includes:
   • Adding or removing units
   • Creating or destroying new relations
   • Changes in workload configuration
   • Upgrading other connected/related/integrated applications simultaneously
   • Backup / restore of snapshots

Upgrade the OpenSearch cluster

To upgrade your OpenSearch cluster, follow these steps:

1. Collect all necessary pre-upgrade information. It will be required for the rollback (if requested). Do NOT skip this step.
2. (optional) Scale-up: The new sacrificial unit will be the first to be updated, and will simplify the rollback procedure in case of the upgrade failure.
3. Prepare the “Charmed OpenSearch” Juju application for the in-place upgrade. See the step description below for all the technical details the charm executes.
4. Upgrade: Only one app unit will be upgraded once started. In case of failure, roll back with juju refresh.
5. Resume upgrade: The upgrade can be resumed if the upgrade of the first unit is successful. All units in an app will be executed sequentially from the highest to lowest unit number.
6. (optional) Consider rolling back in case of disaster. Please inform and include us in your case scenario troubleshooting to trace the source of the issue and prevent it in the future.
7. (optional) Scale back: Remove no longer necessary units created in step 2 (if any).
8. Post-upgrade check: Ensure all units are in the proper state and the cluster is healthy.

Collect all necessary pre-upgrade information

The first step is to record the revision of the running application, as a safety measure for a rollback action. To accomplish this, run the juju status command and look for the deployed Charmed OpenSearch revision in the command output, e.g.:

Model  Controller   Cloud/Region         Version  SLA          Timestamp
dev    development  localhost/localhost  3.5.3    unsupported  10:16:46Z

App                       Version  Status  Scale  Charm                     Channel        Rev  Exposed  Message
opensearch                         active      3  opensearch                2/edge         144  no
self-signed-certificates           active      1  self-signed-certificates  latest/stable  155  no

Unit                         Workload  Agent  Machine  Public address  Ports     Message
opensearch/0                 active    idle   0        10.214.176.180  9200/tcp
opensearch/1                 active    idle   1        10.214.176.220  9200/tcp
opensearch/2*                active    idle   2        10.214.176.175  9200/tcp
self-signed-certificates/0*  active    idle   3        10.214.176.31

Machine  State    Address         Inst id        Base          AZ  Message
0        started  10.214.176.180  juju-0c35d2-0  ubuntu@22.04      Running
1        started  10.214.176.220  juju-0c35d2-1  ubuntu@22.04      Running
2        started  10.214.176.175  juju-0c35d2-2  ubuntu@22.04      Running
3        started  10.214.176.31   juju-0c35d2-3  ubuntu@22.04      Running

For this example, the current revision is 144 for OpenSearch.

Scale-up (optional)

Optionally, it is recommended to scale the application up by one unit before upgrading.

The new unit will be the first one to be updated, and it will assert that the upgrade is possible. In case of failure, having the extra unit will ease the rollback procedure, without disrupting service -more in Minor rollback how-to.

juju add-unit opensearch

Wait for the new unit to be up and ready.

Prepare the application for the in-place upgrade

1. IMPORTANT: Create a backup of your cluster

Refer to How to create a backup.

2. Perform the pre-upgrade-check action

After the application has settled, it’s necessary to run the pre-upgrade-check action against the leader unit:

juju run opensearch/leader pre-upgrade-check

The output should be the following:

Running operation 1 with 1 task
  - task 2 on unit-opensearch-2

Waiting for task 2...
result: Charm is ready for upgrade

The action will ensure and check the health of OpenSearch and determine if the charm is well prepared to start an upgrade procedure.

Initiate the upgrade

Use the juju refresh command to trigger the charm upgrade process. You have control over what upgrade you want to apply:

• You can upgrade the charm to the latest revision available in the charm store for a specific channel, in this case, the edge channel:

  juju refresh opensearch --channel 2/edge
  

• You can also upgrade the charm to a specific revision:

  juju refresh opensearch --revision 145
  

• Or you can upgrade the charm using a local charm file:

  juju refresh opensearch --path /path/to/your/charm/file.charm
  

The OpenSearch upgrade will execute only on the highest ordinal unit, for the running example OpenSearch, the juju status will look as follows:

Model  Controller   Cloud/Region         Version  SLA          Timestamp
dev    development  localhost/localhost  3.5.3    unsupported  10:29:07Z

App                       Version  Status   Scale  Charm                     Channel        Rev  Exposed  Message
opensearch                         blocked      4  opensearch                2/edge         145  no       Upgrading. Verify highest unit is healthy & run `resume-upgrade` action. To rollback, `juju refresh` to last revision
self-signed-certificates           active       1  self-signed-certificates  latest/stable  155  no

Unit                         Workload  Agent  Machine  Public address  Ports     Message
opensearch/0                 active    idle   0        10.214.176.180  9200/tcp  OpenSearch 2.15.0 running; Snap rev 56 (outdated); Charmed operator 1+e686854
opensearch/1                 active    idle   1        10.214.176.220  9200/tcp  OpenSearch 2.15.0 running; Snap rev 56 (outdated); Charmed operator 1+e686854
opensearch/2*                active    idle   2        10.214.176.175  9200/tcp  OpenSearch 2.15.0 running; Snap rev 56 (outdated); Charmed operator 1+e686854
opensearch/3                 active    idle   4        10.214.176.7    9200/tcp  OpenSearch 2.16.0 running; Snap rev 57; Charmed operator 1+e686854
self-signed-certificates/0*  active    idle   3        10.214.176.31

Machine  State    Address         Inst id        Base          AZ  Message
0        started  10.214.176.180  juju-0c35d2-0  ubuntu@22.04      Running
1        started  10.214.176.220  juju-0c35d2-1  ubuntu@22.04      Running
2        started  10.214.176.175  juju-0c35d2-2  ubuntu@22.04      Running
3        started  10.214.176.31   juju-0c35d2-3  ubuntu@22.04      Running
4        started  10.214.176.7    juju-0c35d2-4  ubuntu@22.04      Running
    

Resume upgrade

After the first unit is upgraded, the charm will set the unit upgrade state as completed. If deemed necessary, you can further assert the success of the upgrade. If the unit is healthy within the cluster, the next step is to resume the upgrade process by running:

juju run opensearch/leader resume-upgrade

The resume-upgrade action will roll out the OpenSearch upgrade for the remaining units in the application. The action will be executed sequentially from the highest unit number to the lowest.

After every unit is upgraded, its status will be set to active/idle and its message will indicate the new version of OpenSearch running on the unit. The juju status output will look as follows:

Model  Controller   Cloud/Region         Version  SLA          Timestamp
dev    development  localhost/localhost  3.5.3    unsupported  10:39:06Z

App                       Version  Status       Scale  Charm                     Channel        Rev  Exposed  Message
opensearch                         maintenance      4  opensearch                2/edge         145  no       Upgrading. To rollback, `juju refresh` to the previous revision
self-signed-certificates           active           1  self-signed-certificates  latest/stable  155  no

Unit                         Workload  Agent      Machine  Public address  Ports     Message
opensearch/0                 active    idle       0        10.214.176.180  9200/tcp  OpenSearch 2.15.0 running; Snap rev 56 (outdated); Charmed operator 1+e686854
opensearch/1                 waiting   executing  1        10.214.176.220  9200/tcp  Waiting for OpenSearch to start...
opensearch/2*                active    idle       2        10.214.176.175  9200/tcp  OpenSearch 2.16.0 running; Snap rev 57; Charmed operator 1+e686854
opensearch/3                 active    idle       4        10.214.176.7    9200/tcp  OpenSearch 2.16.0 running; Snap rev 57; Charmed operator 1+e686854
self-signed-certificates/0*  active    idle       3        10.214.176.31

Machine  State    Address         Inst id        Base          AZ  Message
0        started  10.214.176.180  juju-0c35d2-0  ubuntu@22.04      Running
1        started  10.214.176.220  juju-0c35d2-1  ubuntu@22.04      Running
2        started  10.214.176.175  juju-0c35d2-2  ubuntu@22.04      Running
3        started  10.214.176.31   juju-0c35d2-3  ubuntu@22.04      Running
4        started  10.214.176.7    juju-0c35d2-4  ubuntu@22.04      Running

Once all units are upgraded, the application status will be set to active and the message indicating the new version of OpenSearch running on the units will disappear.

Model  Controller   Cloud/Region         Version  SLA          Timestamp
dev    development  localhost/localhost  3.5.3    unsupported  10:43:41Z

App                       Version  Status  Scale  Charm                     Channel        Rev  Exposed  Message
opensearch                         active      4  opensearch                2/edge         145  no
self-signed-certificates           active      1  self-signed-certificates  latest/stable  155  no

Unit                         Workload  Agent  Machine  Public address  Ports     Message
opensearch/0                 active    idle   0        10.214.176.180  9200/tcp
opensearch/1                 active    idle   1        10.214.176.220  9200/tcp
opensearch/2*                active    idle   2        10.214.176.175  9200/tcp
opensearch/3                 active    idle   4        10.214.176.7    9200/tcp
self-signed-certificates/0*  active    idle   3        10.214.176.31

Machine  State    Address         Inst id        Base          AZ  Message
0        started  10.214.176.180  juju-0c35d2-0  ubuntu@22.04      Running
1        started  10.214.176.220  juju-0c35d2-1  ubuntu@22.04      Running
2        started  10.214.176.175  juju-0c35d2-2  ubuntu@22.04      Running
3        started  10.214.176.31   juju-0c35d2-3  ubuntu@22.04      Running
4        started  10.214.176.7    juju-0c35d2-4  ubuntu@22.04      Running

Notice the Rev column in the juju status output. The revision number should reflect the new revision of the application.

Rollback (optional)

In case of a failed upgrade, you can roll back to the previous revision. To do so, follow the guide How to perform a minor rollback.

Scale-back (optional)

If you scaled up the application in step 2, you can now scale it back down to the original number of units:

juju remove-unit opensearch/<highest unit number>

Check the cluster health

First, check the units have settled as `active/idle” state on juju status, with the newer revision number:

Model  Controller   Cloud/Region         Version  SLA          Timestamp
dev    development  localhost/localhost  3.5.3    unsupported  10:45:39Z

App                       Version  Status  Scale  Charm                     Channel        Rev  Exposed  Message
opensearch                         active      3  opensearch                2/edge         145  no
self-signed-certificates           active      1  self-signed-certificates  latest/stable  155  no

Unit                         Workload  Agent  Machine  Public address  Ports     Message
opensearch/0                 active    idle   0        10.214.176.180  9200/tcp
opensearch/1                 active    idle   1        10.214.176.220  9200/tcp
opensearch/2*                active    idle   2        10.214.176.175  9200/tcp
self-signed-certificates/0*  active    idle   3        10.214.176.31

Machine  State    Address         Inst id        Base          AZ  Message
0        started  10.214.176.180  juju-0c35d2-0  ubuntu@22.04      Running
1        started  10.214.176.220  juju-0c35d2-1  ubuntu@22.04      Running
2        started  10.214.176.175  juju-0c35d2-2  ubuntu@22.04      Running
3        started  10.214.176.31   juju-0c35d2-3  ubuntu@22.04      Running

Check the cluster is healthy. OpenSearch’s upstream documentation suggests the following check:

GET "/_cluster/health?pretty"

The response should look similar to the following example:

{
  "cluster_name" : "opensearch-wvmy",
  "status" : "green",
  "timed_out" : false,
  "number_of_nodes" : 3,
  "number_of_data_nodes" : 3,
  "discovered_master" : true,
  "discovered_cluster_manager" : true,
  "active_primary_shards" : 5,
  "active_shards" : 15,
  "relocating_shards" : 0,
  "initializing_shards" : 0,
  "unassigned_shards" : 0,
  "delayed_unassigned_shards" : 0,
  "number_of_pending_tasks" : 0,
  "number_of_in_flight_fetch" : 0,
  "task_max_waiting_in_queue_millis" : 0,
  "active_shards_percent_as_number" : 100.0
}