On 6/3/2016 1:44 PM, Nomar Morado wrote: > Is there any settings to override the quorum rule? Would you know the > rationale behind it? Ideally, you will want to operate the application > even if at least one data center is up.
I do not know if the quorum rule can be overridden, or whether your application can tell the difference between a loss of quorum and zookeeper going down entirely. I really don't know anything about zookeeper client code or zookeeper internals. >From what I understand, majority quorum is the only way to be *completely* sure that cluster software like SolrCloud or your application can handle write operations with confidence that they are applied correctly. If you lose quorum, which will happen if only one DC is operational, then your application should go read-only. This is what SolrCloud does. I am a committer on the Apache Solr project, and Solr uses zookeeper when it is running in SolrCloud mode. The cloud code is handled by other people -- I don't know much about it. I joined this list because I wanted to have the ZK devs include a clarification in zookeeper documentation -- oddly enough, related to the very thing we are discussing. I wanted to be sure that the documentation explicitly mentioned that three serversare required for a fault-tolerant setup. Some SolrCloud users don't want to accept this as a fact, and believe that two servers should be enough. Thanks, Shawn
