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From Fabrice Facorat <fabrice.faco...@gmail.com>
Subject Re: Schema Changes
Date Thu, 17 Nov 2016 12:58:34 GMT
Schema are propagated by GOSSIP

you can check schema propagation cluster wide with nodetool describecluster
or "nodetool gossipinfo | grep SCHEMA | cut -f3 -d: | sort | uniq -c"

You'd better send your DDL instruction to only one node (for example by
using the whitelist load balancing policy with only 1 host specified), this
way your schemas changes will be serialized and you will avoid issues and
race conditions



2016-11-15 19:04 GMT+01:00 Josh Smith <jsmith@ionicsecurity.com>:

> Would someone please explain how schema changes happen?
>
> Here are some of the ring details
>
> We have 5 nodes in 1 DC and 5 nodes in another DC across the country.
>
> Here is our problem, we have a tool which automates our schema creation.
> Our schema consists of 7 keyspaces with 21 tables in each keyspace, so a
> total of 147 tables are created at the initial provisioning.  During this
> schema creation we end up with system_schema keyspace corruption, we have
> found that it is due to schema version disagreement. To combat this we
> setup a wait until there is only one version in both system.local and
> system.peers tables.
>
> The way I understand it schema changes are made on the local node only;
> changes are then propagated through either Thrift or Gossip, I could not
> find a definitive answer online if thrift or gossip was the carrier. So if
> I make all of the schema changes to one node it should propagate the
> changes to the other nodes one at a time. This is how I used to think that
> schema changes are propagated but we still get schema disagreement when
> changing the schema only on one node. Is the only option to introduce a
> wait after every table creation?  Should we be looking at another table
> besides system.local and peers? Any help would be appreciated.
>
>
>
> Josh Smith
>



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