= Activation Sequence Tools
:idprefix:
:idseparator: -

You can use the Artemis CLI to execute activation sequence maintenance/recovery tools for xref:ha.adoc#replication[Replication] with Pluggable Lock Manager.

The 2 main commands are `activation list` and `activation set`, that can be used together to recover some disaster happened to local/coordinated activation sequences.

Here is a disaster scenario built around the RI (using https://zookeeper.apache.org/[Apache ZooKeeper] and https://curator.apache.org/[Apache curator]) to demonstrate the usage of such commands.

== ZooKeeper cluster disaster

A proper ZooKeeper cluster should use at least 3 nodes, but what happens if all these nodes crash loosing any activation state information required to manage replication?

During the disaster (i.e. ZooKeeper nodes are no longer reachable) the follow occurs:

* Active brokers shutdown (and if restarted, should hang waiting to reconnect to the ZooKeeper cluster again)
* Passive brokers unpair and wait to reconnect to the ZooKeeper cluster again

Necessary administrative action:

. Stop all brokers
. Restart ZooKeeper cluster
. Search for brokers with the highest local activation sequence for their `NodeID` by running this command from the `bin` folder of the broker:
+
[,bash]
----
$ ./artemis activation list --local
Local activation sequence for NodeID=7debb3d1-0d4b-11ec-9704-ae9213b68ac4: 1
----

. From the `bin` folder of the brokers with the highest local activation sequence
+
[,bash]
----
# assuming 1 to be the highest local activation sequence obtained at the previous step
# for NodeID 7debb3d1-0d4b-11ec-9704-ae9213b68ac4
$ ./artemis activation set --remote --to 1
Forced coordinated activation sequence for NodeID=7debb3d1-0d4b-11ec-9704-ae9213b68ac4 from 0 to 1
----

. Restart all brokers: previously active ones should be able to be active again

The more ZooKeeper nodes there are the less chance that a disaster like this requires administrative intervention because it allows the ZooKeeper cluster to tolerate more failures.
