Comment 9 for bug 1417874

An environment variable detailing the lifecycle would solve a related issue (the second paragraph in the original bug report), and would certainly help or solve many situations.

However, this particular issue is that when a unit's -departed hooks are run it may find that the related units have already departed the relation and have cut off all access. A Cassandra node has no opportunity to decommission itself cleanly, because it is no longer able to communicate with the rest of the cluster and migrate its data to the remaining nodes. Its particularly important if data is being stored without redundancy (replication factor == 1), because in this case the data is lost. Without the extra hook, removing a node from a cluster is the same as a failure and requires the cluster to be repaired. With the extra hook, the node may decommission itself cleanly and we don't need to repair the cluster and we never have a period of time with reduced data redundancy.