busbey commented on a change in pull request #1167: Hbase 18095: Zookeeper-less client connection implementation URL: https://github.com/apache/hbase/pull/1167#discussion_r378918970
########## File path: src/main/asciidoc/_chapters/architecture.adoc ########## @@ -577,11 +644,24 @@ If the active Master loses its lease in ZooKeeper (or the Master shuts down), th [[master.runtime]] === Runtime Impact -A common dist-list question involves what happens to an HBase cluster when the Master goes down. +A common dist-list question involves what happens to an HBase cluster when the Master goes down. This information has changed staring 3.0.0. + +==== Up until releases 2.x.y Because the HBase client talks directly to the RegionServers, the cluster can still function in a "steady state". Additionally, per <<arch.catalog>>, `hbase:meta` exists as an HBase table and is not resident in the Master. However, the Master controls critical functions such as RegionServer failover and completing region splits. So while the cluster can still run for a short time without the Master, the Master should be restarted as soon as possible. +==== Staring release 3.0.0 +As mentioned in section <<client.masterregistry>>, the default connection registry for clients is now based on master rpc end points. Hence the requirements for +masters' uptime are even tighter starting this release. + +- At least one active or stand by master is needed for a connection set up, unlike before when all the clients needed was a ZooKeeper ensemble. +- Master is now in critical path for read/write operations. For example, if the meta region bounces off to a different region server, clients +need master to fetch the new locations. Earlier this was done by fetching this information directly from ZooKeeper. +- Masters will now have higher connection load than before. So, the server side configuration might need adjustment depending on the load. + +Overall, the master uptime requirements starting with this version are even higher for the client operations to go through. Review comment: Should phrase this change in uptime needs of the master ensemble in terms of when the feature is enabled rather than in terms of hbase versions. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
