Thanks guys, this makes sense I guess, from Solr's side. Perhaps we can have a new Collections API like REDIRECTREPLICA or something, that will redirect a replica to the new node. This API can simply do ADDREPLICA on the new node, and DELETEREPLICA of the node that doesn't exist anymore.
I guess I need to implement that for my use case now (I know that if a node came down, it won't ever come back up again - there will be a new node replacing it), so I'll see how it plays out and if it works well, I'll open a JIRA issue. In my case, when the new node comes up, it can check the cluster's status, and if it detects an orphanage replica, it will add itself as a new replica and delete the orphanage one. Let me know if you see a problem with how I intend to address that. Shai On Tue, Mar 24, 2015 at 6:01 PM, Anshum Gupta <ans...@anshumgupta.net> wrote: > Yes, it applies to both. Solr wouldn't auto-add replicas in either of those > cases (or any other case) to meet the rf specified at create time. > > On Tue, Mar 24, 2015 at 2:22 AM, Shai Erera <ser...@gmail.com> wrote: > > > Thanks Anshum, > > > > About #3, i line with my answer to the previous question, Solr wouldn't > > > auto-add a Replica to meet the replication factor when a node goes > down. > > > > > > > Just to make sure the answer applies to both these cases: > > > > 1. There are two replicas on node1 and node2. Solr won't add a replica > > to node1 when node2 goes down. > > 2. The collection was created with rf=2, Solr creates replicas on > node1 > > and node2. If node2 goes down and a node3 comes up instead, will it be > > assigned a replica, or Solr does not do that also? > > > > In short, is there any scenario where Solr would auto-add replicas (aside > > from running on HDFS) to meet the 'rf' setting, or after the collection > has > > been created, ensuring RF is met is my responsibility? > > > > Shai > > > > On Tue, Mar 24, 2015 at 10:02 AM, Anshum Gupta <ans...@anshumgupta.net> > > wrote: > > > > > Hi Shai, > > > > > > As of now, all replicas for a collections are created to meet the > > specified > > > replication factor at the time of collection creation. There's no way > to > > > defer that until more nodes are up. Your best bet is to have the nodes > > > already up before you CREATE the collection or create the collection > > with a > > > lower replication factor and then use ADDREPLICA. > > > > > > About auto-addition of replicas, that's kind of supported when using > > shared > > > file system (HDFS) to host the index. It's doesn't truly work as per > your > > > use-case i.e. it doesn't consider the intended replication factor but > > only > > > brings up a Replica in case all replicas for a node are down, so that > > > SolrCloud continues to be usable. It also doesn't auto-remove replica > > when > > > the old node comes back up. You can read more about this in the > > > "Automatically Add Replicas in SolrCloud" section here: > > > https://cwiki.apache.org/confluence/display/solr/Running+Solr+on+HDFS > > > > > > About #3, i line with my answer to the previous question, Solr wouldn't > > > auto-add a Replica to meet the replication factor when a node goes > down. > > > > > > > > > On Tue, Mar 24, 2015 at 12:36 AM, Shai Erera <ser...@gmail.com> wrote: > > > > > > > Hi > > > > > > > > I saw that we can define maxShardsPerNode when creating a collection, > > > but I > > > > don't see that I can set something similar for replicas. My scenario > is > > > the > > > > following: > > > > > > > > - I setup one Solr node > > > > - Create collection with numShards=1 and replicationFactor=2 > > > > - Hopefully, one replica is created on that node > > > > - When I bring up the second Solr node, the second replica will be > > > > created > > > > > > > > What I see is that both replicas are created on the first node, and > > when > > > I > > > > bring up the second Solr node, none of the replicas are moved. > > > > > > > > I know that I can "move" one replica by calling ADDREPLICA on node2, > > then > > > > DELETEREPLICA on node1, but I was wondering if there's an automated > way > > > to > > > > do that. > > > > > > > > I've also considered creating the collection with replicationFactor=1 > > and > > > > when the second node comes up it will look for shards w/ one replica > > > only, > > > > and assign themselves as the replica. But it means I have to own that > > > piece > > > > of logic, where if Solr already does that, that's better. > > > > > > > > Also, from what I understand, if I create a collection w/ rf=2 and > > there > > > > are two nodes, then each node is assigned a replica. If one of the > > nodes > > > > comes down, and a 3rd node comes up, it will be assigned a replica -- > > is > > > > that correct? > > > > > > > > Another related question, if there are two replicas on node1 and > node2, > > > and > > > > node2 goes down -- will node1 be assigned the second replica as well? > > > > > > > > If this is explained somewhere, I'd appreciate if you can give me a > > > > pointer. > > > > > > > > Shai > > > > > > > > > > > > > > > > -- > > > Anshum Gupta > > > > > > > > > -- > Anshum Gupta >
