About (1), bq: The Solr Admin UI showed that my replication factor changed but otherwise nothing happened.
this is as designed AFAIK. There's nothing built in to Solr to _automatically_ add replicas when this property is changed. My guess is that the MODIFYCOLLECTION code was written to help with editing the ZK nodes, i.e. make it unnecessary to hand-edit the ZK nodes to change things like replication factor without recreating a collection. I've modified the ref guide page to make this more explicit. about (2)... I agree. If you can reliably repeat this (or even better, come up with a test case) it would be worth a JIRA I think. Best, Erick On Mon, May 23, 2016 at 10:46 AM, Hendrik Haddorp <hendrik.hadd...@gmx.net> wrote: > What I find odd is that creating a collection with a replication factor > greater then 1 does seem to not end up with replicas on the same node. > However when one wants to add replicas later on one need to do the whole > placement manually to avoid single point of failures. > > On 23/05/16 15:28, Tom Evans wrote: >> On Mon, May 23, 2016 at 10:37 AM, Hendrik Haddorp >> <hendrik.hadd...@gmx.net> wrote: >>> Hi, >>> >>> I have a SolrCloud 6.0 setup and created my collection with a >>> replication factor of 1. Now I want to increase the replication factor >>> but would like the replicas for the same shard to be on different nodes, >>> so that my collection does not fail when one node fails. I tried two >>> approaches so far: >>> >>> 1) When I use the collections API with the MODIFYCOLLECTION action [1] I >>> can set the replication factor but that did not result in the creation >>> of additional replicas. The Solr Admin UI showed that my replication >>> factor changed but otherwise nothing happened. A reload of the >>> collection did also result in no change. >>> >>> 2) Using the ADDREPLICA action [2] from the collections API I have to >>> add the replicas to the shard individually, which is a bit more >>> complicated but otherwise worked. During testing this did however at >>> least once result in the replica being created on the same node. My >>> collection was split in 4 shards and for 2 of them all replicas ended up >>> on the same node. >>> >>> So is the only option to create the replicas manually and also pick the >>> nodes manually or is the perceived behavior wrong? >>> >>> regards, >>> Hendrik >>> >>> [1] >>> https://cwiki.apache.org/confluence/display/solr/Collections+API#CollectionsAPI-modifycoll >>> [2] >>> https://cwiki.apache.org/confluence/display/solr/Collections+API#CollectionsAPI-api_addreplica >> >> With ADDREPLICA, you can specify the node to create the replica on. If >> you are using a script to increase/remove replicas, you can simply >> incorporate the logic you desire in to your script - you can also use >> CLUSTERSTATUS to get a list of nodes/collections/shards etc in order >> to inform the logic in the script. This is the approach we took, we >> have a fabric script to add/remove extra nodes to/from the cluster, it >> works well. >> >> The alternative is to put the logic in to Solr itself, using what Solr >> calls a "snitch" to define the rules on where replicas are created. >> The snitch is specified at collection creation time, or you can use >> MODIFYCOLLECTION to set it after the fact. See this wiki patch for >> details: >> >> https://cwiki.apache.org/confluence/display/solr/Rule-based+Replica+Placement >> >> Cheers >> >> Tom >
