![]() ![]() Refer to ZK Documentation for more information. All ZK servers should use the same configuration.By default 3 transaction logs are retained and this is controlled by autopurge.snapRetainCount in zoo.cfg. This would ensure that the older transaction logs are cleaned up regularly and avoids disk full situations. In ZK version 3.4.0 and above, enable auto purging of transaction logs using autopurge.purgeInterval=1 in zoo.cfg.These can be defined in zoo.cfg using dataDir and dataLogDir parameters. Try to keep the Zookeeper log transaction and data dir to be in independent disks.This can be verified by doing a cat /opt/imply-2.8.7/var/zk/myid on server.1 (172.16.xxx.x1) For example, if dataDir is defined as /opt/imply-2.8.7/var/zk, on server.1, myid file should have an entry of 1. In the dataDir for the respective ZK servers, ensure that the myid file has the same number as defined by server.x in the above.When running in HA mode, add all ZK server IP's to zoo.cfg to ensure that ZK can properly elect its own leader:.The reason for this is that there are some bugs in the part of the ZK code that handles DNS mappings, including one where ZK won't retry the connection if DNS becomes unavailable.Įxample : druid.zk.service.host=172.16.xxx.x1,172.16.xxx.x2,172.16.xxx.x3 List ZK IP's as hosts rather than DNS names in the.If possible use high speed disks like SSD's for dataDir and dataLogDir locations. Note that, it isn't enough to just have partitions but they have to be different disks to ensure performance. package to suit your needs Transportation fees are 1.50 per mile round trip for Barnyard Zoo or Exotic Zoo packages and 3. Ideally the ZK data and ZK transaction log files should be on different disks, so that they don't contend for the IO resource. ZK Data and Log files should be on disks, which have least contention from other I/O activities. Because ZK recovery is hampered in this case, it defeats the purpose of high availability. This can work if all ZK servers are healthy, but if one goes down it can be difficult for the client to find a replacement. This is because the coordinator and overlord are normally far less work intensive than data or query nodes Imply prefers to colocate ZK on master nodes rather than data or query nodes. Two ZK's doubles the probability of failure and therefore is actually less preferable than 1 ZK. In a cluster with 2 ZK's, only 1 is needed to maintain a "quorum", so it does not provide high availability. For example, with 3 ZK's, 1 ZK can be lost and the cluster can still function because 2 are left, which = ceil(3/2).Voting decisions include IP discovery, determining which overlord or coordinator is the leader, etc. For increased reliability (high availability), use 3 or 5 ZK's so that it can maintain a quorum in voting decisions (ceiling(n/2)). ![]() Keep a dedicated ZK for Druid avoid sharing with other products / applications.Zookeeper is responsible for much of the communication that keeps the Druid cluster functioning.įor maximum ZK stability, follow these best practices: By design, Druid nodes are prevented from talking to each other. A Druid cluster can only be as stable as its Zookeeper. ![]()
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