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From Stephen Baynes <stephen.bay...@smoothwall.net>
Subject Re: Changing schema on multiple nodes while they are isolated
Date Mon, 05 Oct 2015 08:59:53 GMT
> Why don’t you simply let the node join the cluster? It will pull new
tables and the data automatically.


Because there is no guarantee the rest of the cluster is up, or even if
there is anything more than a cluster of one at this time. This is a plug
in and go environment where the user does not even know or care about the
details of Cassandra. It is not a managed datacenter.

On 2 October 2015 at 17:16, Jacques-Henri Berthemet <
jacques-henri.berthemet@genesys.com> wrote:

> Why don’t you simply let the node join the cluster? It will pull new
> tables and the data automatically.
>
>
>
> *--*
>
> *Jacques-Henri Berthemet*
>
>
>
> *From:* Stephen Baynes [mailto:stephen.baynes@smoothwall.net]
> *Sent:* vendredi 2 octobre 2015 18:08
> *To:* user@cassandra.apache.org
> *Subject:* Re: Changing schema on multiple nodes while they are isolated
>
>
>
> 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.berthemet@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.baynes@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*
>


Thanks
-- 

Stephen Baynes
Senior Developer

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