Hi,
I've noticed in the new Cassandra 0.7.0 release that if I have a
keyspace with a replication level of 2, but only one Cassandra node, I
cannot insert anything into the system. Likely this was a bug in the
old release I was using (0.6.8 -- is there a JIRA describing this
problem?). However, this is a problem for our application, as we don't
want to have to predefine the number of nodes, but rather start with one
node, and add nodes as needed.
Ideally, we could start our system with one node, and be able to insert
data just on that one node. Then, when a second node is added, we can
start using that node to store replicas for the keyspace. I know that
0.7.0 has a new operation for updating keyspace properties like
replication level, but in the documentation there is some mention about
having to run manual repair operations after using it. My question is:
what happens if we do not run these repair operations?
Here's what I'd like to do:
1) Start with a single node with autobootstrap=false and replication
level=1.
2) Later, start a second node with autobootstrap=true and join it to the
first.
3) The application detects that there are now two nodes, and issues the
command to pump up the replication level to 2.
4) If it ever drops back down to one node, it will turn the replication
level down again.
If we do not do a repair, will all hell break lose, or will it just be
the case that data inserted when there was only one node will continue
to be unreplicated, but data inserted when there were two nodes will
have two replicas? Thanks,
Jeremy
