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MariaDB Galera server currently dumps many node's status and cluster membership related information to the server logs. The idea behind this task is to make those information available to the user through INFORMATION_SCHEMA. Following is the sample output :
MariaDB [test]> INSTALL PLUGIN wsrep_status SONAME 'wsrep_status.so'; Query OK, 0 rows affected (0.03 sec) MariaDB [test]> INSTALL PLUGIN wsrep_membership SONAME 'wsrep_status.so'; Query OK, 0 rows affected (0.16 sec) MariaDB [test]> SELECT * FROM INFORMATION_SCHEMA.WSREP_STATUS; +------------+-------------+----------------+--------------+--------------------------------------+---------------------+-----------------+-----+------------------+ | NODE_INDEX | NODE_STATUS | CLUSTER_STATUS | CLUSTER_SIZE | CLUSTER_STATE_UUID | CLUSTER_STATE_SEQNO | CLUSTER_CONF_ID | GAP | PROTOCOL_VERSION | +------------+-------------+----------------+--------------+--------------------------------------+---------------------+-----------------+-----+------------------+ | 0 | Synced | Primary | 3 | 00b0fbad-6e84-11e4-8a8b-376f19ce8ee7 | 2 | 3 | NO | 3 | +------------+-------------+----------------+--------------+--------------------------------------+---------------------+-----------------+-----+------------------+ 1 row in set (0.00 sec) MariaDB [test]> SELECT * FROM INFORMATION_SCHEMA.WSREP_MEMBERSHIP; +-------+--------------------------------------+-------+-----------------+ | INDEX | UUID | NAME | ADDRESS | +-------+--------------------------------------+-------+-----------------+ | 0 | 46da96e3-6e9e-11e4-95a2-f609aa5444b3 | node1 | 10.0.2.15:16000 | | 1 | 5f6bc72a-6e9e-11e4-84ed-57ec6780a3d3 | node2 | 10.0.2.15:16001 | | 2 | 7473fd75-6e9e-11e4-91de-0b541ad91bd0 | node3 | 10.0.2.15:16002 | +-------+--------------------------------------+-------+-----------------+ 3 rows in set (0.00 sec)
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Ok to push. Just a question, can you query these even in case when
1) WITH_WSREP is not defined ?
2) wsrep_on == FALSE ?
(1) Without WITH_WSREP, this plugin won't get build. Also, if we forcefully try to INSTALL this
plugin after copying the wsrep_status.so to lib/plugin/, the attempt would fail.
MariaDB [test]> install plugin wsrep_status soname 'wsrep_status.so'; ERROR 1126 (HY000): Can't open shared library '../lib/plugin/wsrep_status.so' (errno: 2, undefined symbol: LOCK_wsrep_config_state)
(2) When wsrep_on = 0 :
MariaDB [test]> SELECT * FROM INFORMATION_SCHEMA.WSREP_STATUS; +------------+-------------+--------------+--------------------------------------+---------+-----+------------------+ | NODE_INDEX | NODE_STATUS | CLUSTER_SIZE | CLUSTER_UUID | PRIMARY | GAP | PROTOCOL_VERSION | +------------+-------------+--------------+--------------------------------------+---------+-----+------------------+ | 0 | UNDEFINED | 0 | 00000000-0000-0000-0000-000000000000 | YES | NO | 0 | +------------+-------------+--------------+--------------------------------------+---------+-----+------------------+ 1 row in set (0.00 sec) MariaDB [test]> SELECT * FROM INFORMATION_SCHEMA.WSREP_MEMBERSHIP; Empty set (0.00 sec)
When wsrep is not ready to handle transactions, it is not possible to load the plugin, nor to query the tables.
Should it be a opened as another feature request, or can we follow up this here ?
MariaDB [(none)]> INSTALL SONAME 'wsrep_status'; ERROR 1047 (08S01): WSREP has not yet prepared node for application use MariaDB [(none)]> SELECT * FROM INFORMATION_SCHEMA.WSREP_MEMBERSHIP; ERROR 1047 (08S01): WSREP has not yet prepared node for application use
Since INSTALL gets replicated, I think having it wait for the node to get ready seem OK. On the other
hand, detaching I_S queries from wsrep_ready sound like a perfectly valid use case. I have opened
an FR with upstream.
https://github.com/codership/mysql-wsrep/issues/36
http://lists.askmonty.org/pipermail/commits/2014-November/006905.html