arangodb/Documentation/Books/Manual/Administration/Cluster

Cluster administration

This Section includes information related to the administration of an ArangoDB Cluster.

For a general introduction to the ArangoDB Cluster, please refer to the Cluster chapter.

Replacing/Removing a Coordinator

Coordinators are effectively stateless and can be replaced, added and removed without more consideration than meeting the necessities of the particular installation.

To take out a Coordinator stop the Coordinator's instance by issueing kill -SIGTERM <pid>.

Ca. 15 seconds later the cluster UI on any other Coordinator will mark the Coordinator in question as failed. Almost simultaneously, a trash bin icon will appear to the right of the name of the Coordinator. Clicking that icon will remove the Coordinator from the coordinator registry.

Any new Coordinator instance that is informed of where to find any/all agent/s, --cluster.agency-endpoint <some agent endpoint> will be integrated as a new Coordinator into the cluster. You may also just restart the Coordinator as before and it will reintegrate itself into the cluster.

Replacing/Removing a DBServer

DBServers are where the data of an ArangoDB cluster is stored. They do not publish a we UI and are not meant to be accessed by any other entity than Coordinators to perform client requests or other DBServers to uphold replication and resilience.

The clean way of removing a DBServer is to first releave it of all its responsibilities for shards. This applies to followers as well as leaders of shards. The requirement for this operation is that no collection in any of the databases has a relicationFactor greater or equal to the current number of DBServers minus one. For the pupose of cleaning out DBServer004 for example would work as follows, when issued to any Coordinator of the cluster:

curl <coord-ip:coord-port>/_admin/cluster/cleanOutServer -d '{"id":"DBServer004"}'

After the DBServer has been cleaned out, you will find a trash bin icon to the right of the name of the DBServer on any Coordinators' UI. Clicking on it will remove the DBServer in questiuon from the cluster.

Firing up any DBServer from a clean data directory by specifying the any of all agency endpoints will integrate the new DBServer into the cluster.

To distribute shards onto the new DBServer either click on the Distribute Shards button at the bottom of the Shards page in every database.