Hi Stephen, If you manage to create tables on each node while node A and B are separated, you’ll get into troubles when they will reconnect again. I had the case previously and Cassandra complained that tables with same names but different ids were present in the keyspace. I don’t know if there is a way to fix that with nodetool but I don’t think that it is a good practice.
To solve this, we have a “schema creator” application node that is responsible to change the schema. If this node is down, schema updates are not possible. We can make any node ‘creator’, but only one can be enabled at any given time. -- Jacques-Henri Berthemet From: Stephen Baynes [mailto:[email protected]] Sent: vendredi 2 octobre 2015 16:46 To: [email protected] Subject: Changing schema on multiple nodes while they are isolated Is it safe to make schema changes ( e.g. create keyspace and tables ) on multiple separate nodes of a cluster while they are out of communication with other nodes in the cluster? For example create on node A while node B is down, create on node B while A is down, then bring both up together. We are looking to embed Cassandra invisibly in another product and we have no control in what order users may start/stop the nodes up or add/remove them from clusters. And Cassandra must come up and be working with at least local access regardless. So this means always creating keyspaces and tables so they are always present. But this means nodes joining clusters which already have the same keyspace and table defined. Will it cause any issues? I have done some testing and saw some some issues when I tried to nodetool repair to bring things into sync. However at the time I was fighting with what I later discovered was CASSANDRA-9689 keyspace does not show in describe list, if create query times out.<https://issues.apache.org/jira/browse/CASSANDRA-9689> and did not know what was what. I will give it another try sometime, but would appreciate knowing if this is going to run into trouble before we find it. We are basically using Cassandra to share fairly transient information We can cope with data loss during environment changes and occasional losses at other times. But if the environment is stable then it should all just work, whatever the environment is. We use a very high replication factor so all nodes have a copy of all the data and will keep working even if they are the only one up. Thanks -- Stephen Baynes
