Galera
Some galera tricks
Recover Disaster
Restart a stopped Galera Cluster
On one of the node change safe_to_bootstrap to 1 in /var/lib/mysql/grastate.dat
# GALERA saved state
version: 2.1
uuid: 34546540-er30-1223-rsa0-23343fesf25c
seqno: -1
cert_index:
safe_to_bootstrap: 1
On a running node `seqno: -1` is a normal behaviour, in case of crash find the highest to be sure to bootstrap from the safety node
Start a new cluster
$ galera_new_cluster
The others nodes
$ systemctl restart mariadb
Monitoring Galera Cluster
Show all wsrep
MariaDB [(none)]> SHOW GLOBAL STATUS LIKE 'wsrep_%';
Check cluster integrity
MariaDB [(none)]> SHOW GLOBAL STATUS LIKE 'wsrep_cluster_state_uuid';
Show cluster size
MariaDB [(none)]> SHOW GLOBAL STATUS LIKE 'wsrep_cluster_size';
Show cluster status
MariaDB [(none)]> SHOW GLOBAL STATUS LIKE 'wsrep_cluster_status';
Show node status
Show if the node can accept queries :
MariaDB [(none)]> SHOW GLOBAL STATUS LIKE 'wsrep_ready';
Show if the node has network connectivity to other nodes inside the cluster :
MariaDB [(none)]> SHOW GLOBAL STATUS LIKE 'wsrep_connected';
Show the node state :
MariaDB [(none)]> SHOW GLOBAL STATUS LIKE 'wsrep_local_state_comment';
The typical values are :
- Joining
- Waiting
- SST
- Joined
- Synced
- Donor
Format unreadable output
Running queries on wide tables using the MySQL command line can often result in unreadable output:
SELECT * FROM mysql.user;
+----------------------------+-----------------+-------------------------------------------+-------------+-------------+------- ------+-------------+-------------+-----------+-------------+---------------+--------------+-----------+------------+---------- -------+------------+------------+--------------+------------+-----------------------+------------------+--------------+------- ----------+------------------+------------------+----------------+---------------------+--------------------+------------------ +------------+--------------+------------------------+----------+------------+-------------+--------------+---------------+---- ---------+-----------------+----------------------+--------+-----------------------+
| Host | User | Password | Select_priv | Insert_priv | Update _priv | Delete_priv | Create_priv | Drop_priv | Reload_priv | Shutdown_priv | Process_priv | File_priv | Grant_priv | Reference s_priv | Index_priv | Alter_priv | Show_db_priv | Super_priv | Create_tmp_table_priv | Lock_tables_priv | Execute_priv | Repl_s lave_priv | Repl_client_priv | Create_view_priv | Show_view_priv | Create_routine_priv | Alter_routine_priv | Create_user_priv | Event_priv | Trigger_priv | Create_tablespace_priv | ssl_type | ssl_cipher | x509_issuer | x509_subject | max_questions | max _updates | max_connections | max_user_connections | plugin | authentication_string |
+----------------------------+-----------------+-------------------------------------------+-------------+-------------+------- ------+-------------+-------------+-----------+-------------+---------------+--------------+-----------+------------+---------- -------+------------+------------+--------------+------------+-----------------------+------------------+--------------+------- ----------+------------------+------------------+----------------+---------------------+--------------------+------------------ +------------+--------------+------------------------+----------+------------+-------------+--------------+---------------+---- ---------+-----------------+----------------------+--------+-----------------------+
| % | someuser | | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | | | | | 0 | 0 | 0 | 0 | | |
| localhost | someuser | | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | | | | | 0 | 0 | 0 | 0 | | |
You can format this output so that the columns are displayed as key: value pairs by using \G rather than ;, like so:
SELECT * FROM mysql.user \G
*************************** 1. row ***************************
Host: localhost
User: someuser
Password:
Select_priv: N
Insert_priv: N
Update_priv: N
Delete_priv: N
Create_priv: N
Drop_priv: N
Reload_priv: N
Shutdown_priv: N
Process_priv: N
File_priv: N
Grant_priv: N
References_priv: N
Index_priv: N
Alter_priv: N
Show_db_priv: N
Super_priv: N
Create_tmp_table_priv: N
Lock_tables_priv: N
Execute_priv: N
Repl_slave_priv: N
Repl_client_priv: N
Create_view_priv: N
Show_view_priv: N
Create_routine_priv: N
Alter_routine_priv: N
Create_user_priv: N
Event_priv: N
Trigger_priv: N
Create_tablespace_priv: N
ssl_type:
ssl_cipher:
x509_issuer:
x509_subject:
max_questions: 0
max_updates: 0
max_connections: 0
max_user_connections: 0
plugin:
authentication_string:
*************************** 12. row ***************************
Host: %
User: someuser
Password:
Select_priv: N
Insert_priv: N
Update_priv: N
Delete_priv: N
Create_priv: N
Drop_priv: N
Reload_priv: N
Shutdown_priv: N
Process_priv: N
File_priv: N
Grant_priv: N
References_priv: N
Index_priv: N
Alter_priv: N
Show_db_priv: N
Super_priv: N
Create_tmp_table_priv: N
Lock_tables_priv: N
Execute_priv: N
Repl_slave_priv: N
Repl_client_priv: N
Create_view_priv: N
Show_view_priv: N
Create_routine_priv: N
Alter_routine_priv: N
Create_user_priv: N
Event_priv: N
Trigger_priv: N
Create_tablespace_priv: N
ssl_type:
ssl_cipher:
x509_issuer:
x509_subject:
max_questions: 0
max_updates: 0
max_connections: 0
max_user_connections: 0
plugin:
authentication_string: