Upgrade to 0.24 without downtime?

[DaanDD]

When looking at the instructions on how to upgrade to 0.24 it involves deleting the old CHK installation and creating a new one. The ClickHouse instance I'm running is constantly being written to so I cannot just turn off Keeper. Is there a way to upgrade to 0.24 without downtime?
Maybe I could create a new Keeper installation that syncs data with the existing one, then hot swap between old and new Keeper?

[UnamedRus]

Hi,

We are currently in process of writing procedure to migrate CHK from old to new syntax.

Maybe I could create a new Keeper installation that syncs data with the existing one, then hot swap between old and new Keeper?

Yeah, it's basically how it will work:

1. Detach old CHK from operator management.
2. Upgrade Operator + CRDs
3. Create new CHK, which will also include old nodes in it's files.xml configuration.
4. Update config for old keeper installation (ie include new nodes)
5. Check sync
6. Switch CH to new keeper ensemble.
7. Remove old nodes from ensemble
8. Drop old nodes.

[zeev1079]

have a couple of questions regarding this migration process(which looks much straight forward):

1. What happens if the old Keeper nodes have different volume mount paths, such as:

keeper_server/log_storage_path: /var/lib/clickhouse-keeper/logs 
keeper_server/snapshot_storage_path: /var/lib/clickhouse-keeper/snapshots
keeper_server/storage_path: /var/lib/clickhouse-keeper

2. Is adding the old Keeper nodes in the files.xml configuration the correct way to include them in the new installation? For example:

  configuration:
    files:
      files.xml: |
        <yandex>
          <zookeeper>
            <node>
              <host>old-keeper-node-1</host>
              <port>2181</port>
            </node>
            <node>
              <host>old-keeper-node-2</host>
              <port>2181</port>
            </node>
            <node>
              <host>old-keeper-node-3</host>
              <port>2181</port>
            </node>
            <node>
              <host>new-keeper-node-1</host>
              <port>2181</port>
            </node>
            <node>
              <host>new-keeper-node-2</host>
              <port>2181</port>
            </node>
            <node>
              <host>new-keeper-node-3</host>
              <port>2181</port>
            </node>
          </zookeeper>
        </yandex>```

[clement94310]

hello
i read the upgrade doc :
https://github.com/Altinity/clickhouse-operator/blob/0.24.0/docs/keeper_migration_from_23_to_24.md

in point 7
how i have to modify the pvc if i have 3 servers ?
volumeClaimTemplates:
- name: default
spec:
...
volumeName: $PV