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What causes a cluster crash in MariaDB Galera?
Depending on the number of nodes failure, we can categorize Galera cluster crashes in the following three scenarios: Out of three scenarios, Full cluster failure is what causes a complete loss of database connectivity. In normal circumstances, nodes will need to restart due to updates and regular maintenance.
Which is the Active Active configuration of MariaDB Galera?
Galera is a multi-master cluster for MariaDB which replicates data using synchronous replication. Galera allows any nodes in the cluster to act as master and write to any node at a time. The active-active configuration of Galera cluster provides more load balancing and fault tolerance since there is no failover.
Why is MariaDB Galera not accepting SQL requests?
Total loss of quorum occurred and the cluster is not accepting any SQL requests. After a hard crash such as this, even if all the nodes come back online the MariaDB service will be unable to start. This is due to the unclean shutdown and none of the nodes were able to do the last commit.
How to reset the Quorum in MariaDB Galera?
The simplest way to reset the quorum is by automatic bootstrap. We can run the following command in the database shell to auto bootstrap the node: This will bootstrap the surviving node to be the primary starting node so other failed nodes can rejoin the cluster.
How to reset quorum in MariaDB Galera Cluster?
We can check it by viewing the content of There are two ways we can reset the quorum so other nodes can rejoin the cluster: The simplest way to reset the quorum is by automatic bootstrap. We can run the following command in the database shell to auto bootstrap the node:
What’s the worst case of a Galera Cluster crash?
This is the worst case scenario of a Galera cluster crash where all nodes have completely crashed resulting seqno value of -1. As mentioned earlier, resist the temptation of running the command galera_new_cluster on a node then trying to rejoin rest of the nodes to the cluster before checking which node has the latest commit.
What happens if all nodes fail in Galera?
In this scenario, all nodes except one fail which causes loss of quorum. At this stage, Galera cluster can no longer process SQL requests. Since one node is still up and running, no data is lost. If failed nodes do come back online they cannot rejoin the cluster, because the cluster does not exist.