Thank you Erick for this fast answer Why is it a best practice to set the zookeeper connection timeout to 30000 instead the default 15000 value?
Regards Dominique Le ven. 15 nov. 2019 à 18:36, Erick Erickson <erickerick...@gmail.com> a écrit : > Dominique: > > In a word, “yes”. You’ve got it. A common misunderstanding is that ZK is > actively involved in queries/updates/whatever. Basically, what ZK is > responsible for is maintaining collection-wide resources, i.e. the current > state of all the replicas, config files, etc., your “global configuration" > and "collection configuration”, which should change very rarely thus rarely > generate writes. > > The “collection state” (including your “nodes state”) information changes > more frequently and generates more writes as nodes come up and down, go > into recovery, etc. That said, for a cluster where all the replicas are > “active” and don’t go away or go into recovery etc, ZK won’t do any writes. > > So the consequence is that when you power up a cluster, there will be a > flurry of write operations managed by the Overseer, but after all the > replicas are up, write activity should pretty much cease. > > As long as the state is steady, i.e. no replicas changing state, each > individual Solr node has a copy of the relevant collection’s “state.json” > znode and has all the information it needs to query or index without asking > Zookeeper without _either_ reading or writing to ZK. > > One rather obscure cause for ZK writes is when using “schemaless” mode. > When a new field is detected, the schema (and thus the collection’s > configuration) is changed, which generates writes.. > > Best, > Erick > > > > On Nov 15, 2019, at 12:06 PM, Dominique Bejean < > dominique.bej...@eolya.fr> wrote: > > > > Hi, > > > > I would like to be certain to understand how Solr use Zookeeper and more > > precisely when Solr write into Zookeeper. > > > > Solr stores various informations in ZK > > > > - globale configuration (autoscaling, security.json) > > - collection configuration (configs) > > - collections state (state.json, leaders, ...) > > - nodes state (live_nodes, overseer) > > > > > > Writes in Zk occur when > > > > - a zookeeper member start or stop > > - a solr node start or stop > > - a configuration is loaded > > - a collection is created, deleted or updated (nearly all call to > > collection, core or config API) > > > > > > Write do not occur during > > > > - SolrJ client creation > > - indexing data (Solrj, HTTP, DIH, ...) > > - searching (Solrj, HTTP) > > > > > > In conclusion, if Solr nodes are stable (no failure, no maintenance), no > > calls to collection, core or config API are done, so there is nearly no > > writes to ZK. > > > > Is it correct ? > > > > > > Regards > > > > Dominique > >
