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Starting a clusterΒΆ

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. The new cluster should be started on the most advanced node. Run the following command to 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 because 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
    

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