Hi Ben, On 03/30/2016 05:27 PM, Ben Pfaff wrote:
I'm in the midst of implementing high availability for OVSDB, based on the Raft algorithm. When I'm done, it should be possible to set up OVSDB clusters with automatic failover. Is this the same use case as your code?
No, in this case the replication works by way of making the second server an OVSDB client, so it gets notified about all the changes in the remote server.
In your case, how many OVSDB servers are required for replication to work? Raft has a quorum requirement of (N/2)+1 servers to be available in order for consensus to be reached. That makes the minimum number of servers 3, if you want to allow one to become unavailable. If you have 2 servers and one goes down, there's no quorum.
The patch Mario is proposing has failover characteristics, not load-distribution characteristics: if one of the servers goes down, the other one can take over because it has a copy of the data up to the last notification the server was able to sent. Also, in the proposed patch transactions are not delayed until consensus is reached, but instead clients are talking only to the active server, which is applying transactions immediately. The active server is notifying the standby about the new data just like it's doing with any other client.
Marcelo _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
