shanyu commented on a change in pull request #212: [LIVY-11] Enable HA support URL: https://github.com/apache/incubator-livy/pull/212#discussion_r320942152
########## File path: server/src/main/scala/org/apache/livy/server/CuratorElectorService.scala ########## @@ -0,0 +1,123 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.livy.server + +import java.io.Closeable +import java.io.IOException +import java.util.concurrent.TimeUnit +import java.util.concurrent.atomic.AtomicInteger + +import org.apache.curator.framework.CuratorFramework +import org.apache.curator.framework.CuratorFrameworkFactory +import org.apache.curator.framework.recipes.leader.LeaderLatch +import org.apache.curator.framework.recipes.leader.LeaderLatchListener +import org.apache.curator.retry.RetryNTimes + +import org.apache.livy.{LivyConf, Logging} +import org.apache.livy.LivyConf.Entry + +object CuratorElectorService { + val HA_KEY_PREFIX_CONF = Entry("livy.server.ha.key-prefix", "livy_ha") + val HA_RETRY_CONF = Entry("livy.server.ha.retry-policy", "5,100") +} + +class CuratorElectorService(livyConf : LivyConf, livyServer : LivyServer) + extends LeaderLatchListener + with Logging +{ + + import CuratorElectorService._ + + val haAddress = livyConf.get(LivyConf.HA_ZOOKEEPER_URL) + require(!haAddress.isEmpty, s"Please configure ${LivyConf.HA_ZOOKEEPER_URL.key}.") + val haKeyPrefix = livyConf.get(HA_KEY_PREFIX_CONF) + val retryValue = livyConf.get(HA_RETRY_CONF) + // a regex to match patterns like "m, n" where m and n both are integer values + val retryPattern = """\s*(\d+)\s*,\s*(\d+)\s*""".r + val retryPolicy = retryValue match { + case retryPattern(n, sleepMs) => new RetryNTimes(n.toInt, sleepMs.toInt) + case _ => throw new IllegalArgumentException( + s"$HA_KEY_PREFIX_CONF contains bad value: $retryValue. " + + "Correct format is <max retry count>,<sleep ms between retry>. e.g. 5,100") + } + + val client: CuratorFramework = CuratorFrameworkFactory.newClient(haAddress, retryPolicy) + val leaderKey = s"/$haKeyPrefix/leader" + + var server : LivyServer = livyServer + + var leaderLatch = new LeaderLatch(client, leaderKey) + leaderLatch.addListener(this) + + object HAState extends Enumeration{ + type HAState = Value + val Active, Standby = Value + } + var currentState = HAState.Standby + + def isLeader() { + transitionToActive(); + } + + def notLeader(){ + transitionToStandby(); + } + + def start() : Unit = { + transitionToStandby() + + client.start() + leaderLatch.start() + leaderLatch.await() + + // This instance is now the leader. Joining the webserver to the main thread + info("starting join") Review comment: This doesn't seem right. If networking issue caused current active server to be standby, then transitionToStandby() will be called and server will be stopped, and current server process will exit. I think we should do "Thread.currentThread.join()" right after leaderLatch.start() to block forever, with try catch block, and if any exception occurs we transitionToStandby() and exit. ---------------------------------------------------------------- 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: us...@infra.apache.org With regards, Apache Git Services
