Administering

When running a PGD cluster with Group Commit, there are some things you need to be aware of when administering the system, such as how to safely shut down and restart nodes.

Planned shutdown and restarts

When using Group Commit with receive confirmations, take care with planned shutdown or restart. By default, the apply queue is processed prior to shutting down. However, in the immediate shutdown mode, the queue is discarded at shutdown, leading to the stopped node “forgetting” transactions in the queue. A concurrent failure of the origin node can lead to loss of data, as if both nodes failed.

To ensure the apply queue gets flushed to disk, use either smart for maintenance tasks. This approach maintains the required synchronization level and prevents loss of data.