Starting a cluster¶

Gracefully shutting down all nodes destroys the cluster. Starting or restarting a cluster from zero nodes requires creating a new cluster on one of the nodes.

1. Start a new cluster on the most advanced node. Check the seqno value in the grastate.dat file on all of the nodes:

   # ansible galera_container -m shell -a "cat /var/lib/mysql/grastate.dat"
   node2_galera_container-49a47d25 | success | rc=0 >>
   # GALERA saved state version: 2.1
   uuid:    338b06b0-2948-11e4-9d06-bef42f6c52f1
   seqno:   31
   cert_index:
   
   node3_galera_container-3ea2cbd3 | success | rc=0 >>
   # GALERA saved state version: 2.1
   uuid:    338b06b0-2948-11e4-9d06-bef42f6c52f1
   seqno:   31
   cert_index:
   
   node4_galera_container-76275635 | success | rc=0 >>
   # GALERA saved state version: 2.1
   uuid:    338b06b0-2948-11e4-9d06-bef42f6c52f1
   seqno:   31
   cert_index:
   

   In this example, all nodes in the cluster contain the same positive seqno values as they were synchronized just prior to graceful shutdown. If all seqno values are equal, any node can start the new cluster.

   # /etc/init.d/mysql start --wsrep-new-cluster
   

   This command results in a cluster containing a single node. The wsrep_cluster_size value shows the number of nodes in the cluster.

   node2_galera_container-49a47d25 | FAILED | rc=1 >>
   ERROR 2002 (HY000): Can't connect to local MySQL server
   through socket '/var/run/mysqld/mysqld.sock' (111)
   
   node3_galera_container-3ea2cbd3 | FAILED | rc=1 >>
   ERROR 2002 (HY000): Can't connect to local MySQL server
   through socket '/var/run/mysqld/mysqld.sock' (2)
   
   node4_galera_container-76275635 | success | rc=0 >>
   Variable_name             Value
   wsrep_cluster_conf_id     1
   wsrep_cluster_size        1
   wsrep_cluster_state_uuid  338b06b0-2948-11e4-9d06-bef42f6c52f1
   wsrep_cluster_status      Primary
   

2. Restart MariaDB on the other nodes and verify that they rejoin the cluster.

   node2_galera_container-49a47d25 | success | rc=0 >>
   Variable_name             Value
   wsrep_cluster_conf_id     3
   wsrep_cluster_size        3
   wsrep_cluster_state_uuid  338b06b0-2948-11e4-9d06-bef42f6c52f1
   wsrep_cluster_status      Primary
   
   node3_galera_container-3ea2cbd3 | success | rc=0 >>
   Variable_name             Value
   wsrep_cluster_conf_id     3
   wsrep_cluster_size        3
   wsrep_cluster_state_uuid  338b06b0-2948-11e4-9d06-bef42f6c52f1
   wsrep_cluster_status      Primary
   
   node4_galera_container-76275635 | success | rc=0 >>
   Variable_name             Value
   wsrep_cluster_conf_id     3
   wsrep_cluster_size        3
   wsrep_cluster_state_uuid  338b06b0-2948-11e4-9d06-bef42f6c52f1
   wsrep_cluster_status      Primary