IST Basics
State transfers in Galera remain a mystery to most people. Incremental State transfers (as opposed to full State Snapshot transfers) are used under the following conditions:
- The Joiner node reports Galera a valid Galera GTID to the cluster
- The Donor node selected contains all the transactions the Joiner needs to catch up to the rest of the cluster in its Gcache
- The Donor node can establish a TCP connection to the Joiner on port 4568 (by default)
IST states
Galera has many internal node states related to Joiner nodes. They currently are:
- Joining
- Joining: preparing for State Transfer
- Joining: requested State Transfer
- Joining: receiving State Transfer
- Joining: State …