mgao0 commented on a change in pull request #718: Implement Helix nonblocking lock URL: https://github.com/apache/helix/pull/718#discussion_r375597685
########## File path: helix-lock/src/main/java/org/apache/helix/lock/ZKHelixNonblockingLock.java ########## @@ -0,0 +1,200 @@ +/* + * 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.helix.lock; + +import java.util.UUID; + +import com.google.common.annotations.VisibleForTesting; +import org.I0Itec.zkclient.DataUpdater; +import org.apache.helix.AccessOption; +import org.apache.helix.BaseDataAccessor; +import org.apache.helix.HelixException; +import org.apache.helix.ZNRecord; +import org.apache.helix.manager.zk.ZkBaseDataAccessor; +import org.apache.helix.manager.zk.ZkClient; +import org.apache.helix.manager.zk.client.HelixZkClient; +import org.apache.helix.model.HelixConfigScope; +import org.apache.log4j.Logger; +import org.apache.zookeeper.data.Stat; + + +/** + * Helix nonblocking lock implementation based on Zookeeper + */ +public class ZKHelixNonblockingLock implements HelixLock { + + private static final Logger LOG = Logger.getLogger(ZKHelixNonblockingLock.class); + + private static final String LOCK_ROOT = "LOCKS"; + private static final String PATH_DELIMITER = "/"; + private static final String UUID_FORMAT_REGEX = + "[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}"; + private final String _lockPath; + private final String _userId; + private final long _timeout; + private final String _lockMsg; + private final BaseDataAccessor<ZNRecord> _baseDataAccessor; + + /** + * Initialize the lock with user provided information, e.g.,cluster, scope, etc. + * @param clusterName the cluster under which the lock will live + * @param scope the scope to lock + * @param zkAddress the zk address the cluster connects to + * @param timeout the timeout period of the lcok + * @param lockMsg the reason for having this lock + * @param userId a universal unique userId for lock owner identity + */ + public ZKHelixNonblockingLock(String clusterName, HelixConfigScope scope, String zkAddress, + Long timeout, String lockMsg, String userId) { + this(PATH_DELIMITER + clusterName + PATH_DELIMITER + LOCK_ROOT + PATH_DELIMITER + scope, + zkAddress, timeout, lockMsg, userId); + } + + /** + * Initialize the lock with user provided information, e.g., lock path under zookeeper, etc. + * @param lockPath the path of the lock under Zookeeper + * @param zkAddress the zk address of the cluster + * @param timeout the timeout period of the lcok + * @param lockMsg the reason for having this lock + * @param userId a universal unique userId for lock owner identity + */ + private ZKHelixNonblockingLock(String lockPath, String zkAddress, Long timeout, String lockMsg, + String userId) { + HelixZkClient zkClient = new ZkClient(zkAddress); + _lockPath = lockPath; + _timeout = timeout; + _lockMsg = lockMsg; + if (!userId.matches(UUID_FORMAT_REGEX)) { + throw new IllegalArgumentException("The input user id is not a valid UUID."); + } + _userId = userId; + _baseDataAccessor = new ZkBaseDataAccessor<ZNRecord>(zkClient.getServers()); + } + + @Override + public boolean acquireLock() { + + // Set lock information fields + ZNRecord lockInfo = new ZNRecord(_userId); + lockInfo.setSimpleField(ZKHelixNonblockingLockInfo.InfoKey.OWNER.name(), _userId); + lockInfo.setSimpleField(ZKHelixNonblockingLockInfo.InfoKey.MESSAGE.name(), _lockMsg); + long timeout; + + // If the input timeout value is the max value, set the expire time to max value + if (_timeout == Long.MAX_VALUE) { + timeout = _timeout; + } else { + timeout = System.currentTimeMillis() + _timeout; + } + lockInfo + .setSimpleField(ZKHelixNonblockingLockInfo.InfoKey.TIMEOUT.name(), String.valueOf(timeout)); + + // Try to create the lock node + boolean success = _baseDataAccessor.create(_lockPath, lockInfo, AccessOption.PERSISTENT); + + // If fail to create the lock node (acquire the lock), compare the timeout timestamp of current lock node with current time, if already passes the timeout, release current lock and try to acquire the lock again + if (!success) { + Stat stat = new Stat(); + ZNRecord curLock = _baseDataAccessor.get(_lockPath, stat, AccessOption.PERSISTENT); + long curTimeout = + Long.parseLong(curLock.getSimpleField(ZKHelixNonblockingLockInfo.InfoKey.TIMEOUT.name())); + if (System.currentTimeMillis() >= curTimeout) { + // set may fail when the znode version changes in between the get and set, meaning there are some changes in the lock + success = + _baseDataAccessor.set(_lockPath, lockInfo, stat.getVersion(), AccessOption.PERSISTENT); + } + } + return success; + } + + @Override + public boolean releaseLock() { + ZNRecord newLockInfo = new ZNRecord(_userId); + newLockInfo.setSimpleField(ZKHelixNonblockingLockInfo.InfoKey.OWNER.name(), + ZKHelixNonblockingLockInfo.DEFAULT_OWNER_TEXT); + newLockInfo.setSimpleField(ZKHelixNonblockingLockInfo.InfoKey.MESSAGE.name(), + ZKHelixNonblockingLockInfo.DEFAULT_MESSAGE_TEXT); + newLockInfo.setSimpleField(ZKHelixNonblockingLockInfo.InfoKey.TIMEOUT.name(), + ZKHelixNonblockingLockInfo.DEFAULT_TIMEOUT_TEXT); + LockUpdater updater = new LockUpdater(newLockInfo); + return _baseDataAccessor.update(_lockPath, updater, AccessOption.PERSISTENT); + } + + @Override + public ZKHelixNonblockingLockInfo getLockInfo() { + if (!_baseDataAccessor.exists(_lockPath, AccessOption.PERSISTENT)) { + return new ZKHelixNonblockingLockInfo(); + } + ZNRecord curLockInfo = _baseDataAccessor.get(_lockPath, null, AccessOption.PERSISTENT); Review comment: I changed it to only call get once, and didn't use try catch. Instead, if the node doesn't exist, curLockInfo would be null, and I chose to handle it in the constructor of ZKHelixNonblockingLockInfo(ZNRecord). ---------------------------------------------------------------- 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 --------------------------------------------------------------------- To unsubscribe, e-mail: reviews-unsubscr...@helix.apache.org For additional commands, e-mail: reviews-h...@helix.apache.org
