Joining a replication cluster

To join an existing cluster name and any working node should be set. In case of a single cluster path might be omitted, data_dir will be used as the cluster path. For all subsequent clusters path needs to be set and it should be available.


A node joins a cluster by getting the data from the node provided and, if successful, it updates node lists in all the other cluster nodes similar to ALTER CLUSTER ... UPDATE nodes. This list is used to rejoin nodes to the cluster on restart.

There are two lists of nodes. One is used to rejoin nodes to the cluster on restart, it is updated across all nodes same way as ALTER CLUSTER ... UPDATE nodes does. Join cluster does the same update automatically. Cluster status shows this list as cluster_post_nodes_set. The second list is a list of all active nodes used for replication. This list doesn't require manual management. ALTER CLUSTER ... UPDATE nodes actually copies this list of nodes to the list of nodes used to rejoin on restart. Cluster status shows this list as cluster_post_nodes_view.

When nodes are located at different network segments or in different datacenters nodes option may be set explicitly. That allows to minimize traffic between nodes and to use gateway nodes for datacenters intercommunication. The following command joins an existing cluster using the nodes option.

Note: that when this syntax is used, cluster_post_nodes_set list is not updated automatically. Use ALTER CLUSTER ... UPDATE nodes to update it.

JOIN CLUSTER click_query 'clicks_mirror1:9312;clicks_mirror2:9312;clicks_mirror3:9312' as nodes

JOIN CLUSTER completes when a node receives all the necessary data to be in sync with all the other nodes in the cluster.

Deleting a replication cluster

Delete statement removes a cluster specified with name. The cluster gets removed from all the nodes, but its indexes are left intact and become active local non-replicated indexes.

DELETE CLUSTER click_query

Adding and removing an index from a replication cluster

ALTER CLUSTER <cluster_name> ADD <index_name> adds an existing local index to the cluster. The node which receives the ALTER query sends the index to the other nodes in the cluster. All the local indexes with the same name on the other nodes of the cluster get replaced with the new index.

ALTER CLUSTER click_query ADD clicks_daily_index

ALTER CLUSTER <cluster_name> DROP <index_name> forgets about a local index, i.e., it doesn't remove the index files on the nodes but just makes it an active non-replicated index.

ALTER CLUSTER posts DROP weekly_index