On Mon, 2010-10-04 at 00:25 +0530, Arunkumar Ayyavu wrote: > I'm looking at setting up multiple masters for redundancy (for index > updates). I found the thread in this link > (http://www.lucidimagination.com/search/document/68ac303ce8425506/multiple_masters_solr_replication_1_4) > discussed this subject more than a year back. Does Solr support such > configuration today?
Solr does not support master/master replication. When you commit documents to SOLR, it adds a segment to the underlying Lucene index. Replication then syncs that segment to your slaves. To do master/master replication, you would have to pull changes from each master, then merge those changed segments into a single updated index. This is more complex than what is happening in the current Solr replication (which is not much more than an rsync of the index files). Note, if you commit your changes to two masters, you cannot switch a slave between them, as it is unlikely that the two masters will have matching index files. If you did so, you would probably trigger a pull of the entire index across the network, which (while it would likely work) would not be the most efficient action. What you can do is think cleverly about how you organise your master/slave setup. E.g. have a slave that doesn't get queried, but exists to take over the role of the master in case it fails. The index on a slave is the same as that in a master, and can immediately take on the role of the master (receiving commits), and upon failure of your master, you could point your other slaves at this new master, and things should just carry on as before. Also, if you have a lot of slaves (such that they are placing too big a load on your master), insert intermediate hosts that are both slaves off the master, and masters to your query slaves. That way, you could have, say, two boxes slaving off the master, then 20 or 30 slaving off them. > And does Solr support replication between masters? Otherwise, I'll > have to post the updates to all masters to keep the indexes of masters > in sync. Does SolrCloud address this case? (Please note it is too > early for me to read about SolrCloud as I'm still learning Solr) I don't believe SolrCloud is aiming to support master/master replication. HTH Upayavira
