7.3. Checking database node integrity

If you can isolate a Galera cluster problem to a specific node, certain wsrep database variables can indicate the specific problem in the node.

Procedure

Run the following command and replace VARIABLE with the wsrep database variable that you want to check:

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sudo docker exec galera-bundle-docker-0 sudo mysql -B --password="[MYSQL-HIERA-PASSWORD]" -e "SHOW GLOBAL STATUS LIKE 'VARIABLE';"

$ sudo docker exec galera-bundle-docker-0 sudo mysql -B --password="[MYSQL-HIERA-PASSWORD]" -e "SHOW GLOBAL STATUS LIKE 'VARIABLE';"

The following table lists the wsrep database variables that you can use to check node integrity.

表7.2 Database variables to check for node integrity
Variable	Summary	Description
`wsrep_ready`	Node ability to accept queries	States whether the node can accept write-sets from the cluster. If so, then `wsrep_ready` is `ON`.
`wsrep_connected`	Node network connectivity	States whether the node can connect to other nodes on the network. If so, then `wsrep_connected` is `ON`.
`wsrep_local_state_comment`	Node state	Summarizes the node state. If the node can write to the cluster, then typical values for `wsrep_local_state_comment` can be `Joining`, `Waiting on SST`, `Joined`, `Synced`, or `Donor`. If the node is part of a non-operational component, then the value of `wsrep_local_state_comment` is `Initialized`.

注記

The wsrep_connected value can be ON even if the node is connected only to a subset of nodes in the cluster. For example, in case of a cluster partition, the node might be part of a component that cannot write to the cluster. For more information about checking cluster integrity, see 「Checking database cluster integrity」.
If the wsrep_connected value is OFF, then the node is not connected to any cluster components.

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