You could use a two key space method. At startup, wait some time for the node to join the cluster.
the first time the app starts, you can be in one of three states: The happiest state is that you succeed in joining a cluster. in this case you will get replicated the cluster's keyspace and can start using it as normal. the other two cases are exception cases: either you are the only node ever to exist or you are a new node for a cluster that you cannot communicate with. in either of these cases, you create a local private copy of your schema in its own/unique keyspace. you application will use the "private" schema going forward until it receives notification about another node joining the cluster. when this occurs, your app attempts to create the "REAL" schema/keyspace (making liberal use of "if not exists") and (if necessary) migrates the data from it's "private" schema into the "real" schema followed by deleting the "private" schema. There are edge cases and likely race conditions inherent to this method that you would have to deal with, but it should do what you are describing. Clint Hi Jacques-Henri You are right - serious trouble. I managed some more testing and it does not repair or share any data. In the logs I see lots of: WARN [MessagingService-Incoming-/10.50.16.214] 2015-10-02 16:52:36,810 IncomingTcpConnection.java:100 - UnknownColumnFamilyException reading from socket; closing org.apache.cassandra.db.UnknownColumnFamilyException: Couldn't find cfId=e6828dd0-691a-11e5-8a27-b1780df21c7c at org.apache.cassandra.db.ColumnFamilySerializer.deserializeCfId(ColumnFamilySerializer.java:163) ~[apache-cassandra-2.2.1.jar:2.2.1] at org.apache.cassandra.db.ColumnFamilySerializer.deserialize(ColumnFamilySerializer.java:96) ~[apache-cassandra-2.2.1.jar:2.2.1] and some: ERROR [AntiEntropyStage:1] 2015-10-02 16:48:16,546 RepairMessageVerbHandler.java:164 - Got error, removing parent repair session ERROR [AntiEntropyStage:1] 2015-10-02 16:48:16,548 CassandraDaemon.java:183 - Exception in thread Thread[AntiEntropyStage:1,5,main] java.lang.RuntimeException: java.lang.NullPointerException at org.apache.cassandra.repair.RepairMessageVerbHandler.doVerb(RepairMessageVerbHandler.java:167) ~[apache-cassandra-2.2.1.jar:2.2.1] at org.apache.cassandra.net.MessageDeliveryTask.run(MessageDeliveryTask.java:66) ~[apache-cassandra-2.2.1.jar:2.2.1] Will need to do some thinking about this. I wonder about shiping a backup of a good system keyspace and restore it on each node before it starts for the first time - but will that end up with each node having the same internal id? On 2 October 2015 at 16:27, Jacques-Henri Berthemet < jacques-henri.berthe...@genesys.com> wrote: > 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:stephen.bay...@smoothwall.net] > *Sent:* vendredi 2 octobre 2015 16:46 > *To:* user@cassandra.apache.org > *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* > Thanks -- Stephen Baynes
