Fernando: I'd phrase it more strongly than Shawn. Prior to 7.0 all replicas both indexed and search (they were NRT replica), so there wasn't any choice but to index and search on every replica.
It's one of those things that if you have very high throughput (indexing) situations, you _might_ want to use TLOG and/or PULL replicas. But TANSTAAFL (There Ain't No Such Thing As A Free Lunch). TLOG/PULL replicas copy index segments around, which may be up to 5G each (default TieredMergePolicy cap on individual segment sizes), whereas NRT replicas just get the raw document. So in the TLOG/PULL situations, you'll get bursts of network traffic but each replica has less CPU load because all the replicas but one for each shard do not have to index the doc. In the NRT case, the raw documents are forwarded so the network is less bursty, but all of the replicas spend CPU cycles indexing. So I wouldn't worry about it unless you running into performance problems, _then_ I'd investigate TLOG/PULL replicas. Best, Erick On Fri, Nov 9, 2018 at 11:37 AM Shawn Heisey <apa...@elyograg.org> wrote: > > On 11/9/2018 12:13 PM, Fernando Otero wrote: > > I read in several blog posts that it's never a good idea to index and > > search on the same node. I wonder how that can be achieved in Solr Cloud or > > if it happens automatically. > > I would disagree with that blanket assertion. > > Indexing does put extra load on a server that can interfere with query > performance. Whether that will be a real problem pretty much depends on > exactly how much indexing you're doing, and what kind of query load you > need to handle. For extreme scaling, it can be a good idea to separate > indexing and searching. > > With a master/slave architecture, any version of Solr can separate > indexing and querying. > > Before 7.x, it wasn't possible to separate indexing and querying with > SolrCloud. With previous major versions, ALL replicas do the same > indexing. With 7.x, that's still the default behavior, but 7.x has new > replica types that make it possible for indexing to only take place on > shard leaders. The latest version of Solr 7.x has a way to prefer > certain replica types, which is how the separation can be achieved. > > Thanks, > Shawn >
