Changing subject header. I am encountering this issue in Solr 5.3.0 whereby I am getting haywired leader election using SolrCloud. I am using NSSM 2.24 to startup my solr services with zookeeper set as a dependency.
For example, if I have three servers marked as 10.0.0.4, 10.0.0.5 and 10.0.0.6, both 10.0.0.4 and 10.0.0.5 show up as Leaders in Solr Admin Panel. I then decided to manually stop all services, and ensure all Zookeeper services are booted up first prior to starting Solr services on all machines. Then I refreshed my Solr Admin Panel to observe the correct leaders and followers and test node recovery. Everything turned out fine. Hence, the issue is that upon startup of three machines, the startup of ZK and Solr is out of sequence that causes SolrCloud to behave unexpectedly. Noting there is Jira ticket addressed here for Solr 4.9 above to include an improvement to the issue above. (https://issues.apache.org/jira/browse/SOLR-5129) Can someone please advise. Best regards, Adrian -----Original Message----- From: Alessandro Benedetti [mailto:benedetti.ale...@gmail.com] Sent: Tuesday, October 6, 2015 7:14 PM To: solr-user@lucene.apache.org Subject: Re: Zookeeper HA with 3x ZK with Solr server nodes When you have a ZK Ensemble a quorum of active nodes is necessary to have the entire Ensemble to work ( elect leaders, manage the cluster topology etc etc) . The quorum is 50% living nodes +1 . If you have an ensemble of 3 nodes, the quorum is 3/2 +1 = 2 nodes . With an ensemble of 3 nodes, you can lose 1 and the ZK ensemble will continue to work. If you have an ensemble of 5 nodes, the quorum is 5/2 +1 = 3 nodes With an ensemble of 5 nodes, you can lose 2 and the ZK ensemble will continue to work. ect ect Cheers 2015-10-06 10:55 GMT+01:00 Adrian Liew <adrian.l...@avanade.com>: > Hi there, > > > > I have 3 Solr server Azure VM nodes participating in SolrCloud with ZK > installed on each of these nodes (to avoid a single point of failure > with ZK for leader election). Each Solr server is hosted in a Windows > Server > 2012 R2 environment. I was told by my peer that if one zookeeper > service fails, the entire quorum fails. Hence if a quorum fails, does > that mean it will not be able to elect the leader from the remaining 2 > alive Solr servers, even if ZK services are installed in each node? > > > > I am yet to this out as this defeats the purpose of having a ZK > installed on each server. I am afraid if one node fails, a leader > cannot be elected with the remaining two available nodes. Correct me if I am > wrong. > > > > Regards, > > Adrian > > > -- -------------------------- Benedetti Alessandro Visiting card - http://about.me/alessandro_benedetti Blog - http://alexbenedetti.blogspot.co.uk "Tyger, tyger burning bright In the forests of the night, What immortal hand or eye Could frame thy fearful symmetry?" William Blake - Songs of Experience -1794 England
