What is the primary component in a Galera Cluster and why is it important?

Issue

• When Galera starts with the bootstrap command on a node, that particular node will reach Primary state (check the value of wsrep_cluster_status). The remaining nodes will just require a normal start command and they will automatically look for existing Primary Component (PC) in the cluster and join to form a cluster. Data synchronization then happens through either incremental state transfer (IST) or snapshot state transfer (SST) between the joiner and the donor.

One should only bootstrap the Galera cluster if one wants to start a new cluster or when no other nodes in the cluster is in PRIMARY state.

Care should be taken when choosing the action to take, or else one might end up with split clusters or loss of data

More information is available in: How Galera Multi-Master works and what are the main elements involved?