Files

Qin Wang 8cc0125e95 [docs] added a necessary arg for ansible command after removal of

ansible.cfg

ansible.cfg contains defaults, e.g., inventory. The command
ansible galera_container -m shell -a "mysql \
    -h localhost -e 'show status like \"%wsrep_cluster_%\";'"
doesn't work without specifying inventory.

This patch adds the sourcing of the openstack-ansible.rc file
prior to executing any ansible commands.

Change-Id: I59cd398e5f48f3b821ebd475bfe4069c0e142929
closes-bug: 1619062

2016-09-08 12:58:29 +01:00

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Home OpenStack-Ansible Installation Guide

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.

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

# . /usr/local/bin/openstack-ansible.rc
# 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

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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Starting a cluster

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