bharatviswa504 commented on a change in pull request #1006: HDDS-1723. Create new OzoneManagerLock class. URL: https://github.com/apache/hadoop/pull/1006#discussion_r296926683
########## File path: hadoop-ozone/common/src/main/java/org/apache/hadoop/ozone/om/lock/OzoneManagerLock.java ########## @@ -0,0 +1,312 @@ +/** + * 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.hadoop.ozone.om.lock; + + +import java.util.ArrayList; +import java.util.List; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import org.apache.hadoop.conf.Configuration; +import org.apache.hadoop.ozone.lock.LockManager; + +/** + * Provides different locks to handle concurrency in OzoneMaster. + * We also maintain lock hierarchy, based on the weight. + * + * <table> + * <caption></caption> + * <tr> + * <td><b> WEIGHT </b></td> <td><b> LOCK </b></td> + * </tr> + * <tr> + * <td> 0 </td> <td> S3 Bucket Lock </td> + * </tr> + * <tr> + * <td> 1 </td> <td> Volume Lock </td> + * </tr> + * <tr> + * <td> 2 </td> <td> Bucket Lock </td> + * </tr> + * <tr> + * <td> 3 </td> <td> User Lock </td> + * </tr> + * <tr> + * <td> 4 </td> <td> S3 Secret Lock</td> + * </tr> + * <tr> + * <td> 5 </td> <td> Prefix Lock </td> + * </tr> + * </table> + * + * One cannot obtain a lower weight lock while holding a lock with higher + * weight. The other way around is possible. <br> + * <br> + * <p> + * For example: + * <br> + * {@literal ->} acquire volume lock (will work)<br> + * {@literal +->} acquire bucket lock (will work)<br> + * {@literal +-->} acquire s3 bucket lock (will throw Exception)<br> + * </p> + * <br> + */ + +public class OzoneManagerLock { + + private static final Logger LOG = + LoggerFactory.getLogger(OzoneManagerLock.class); + + private final LockManager<String> manager; + private final ThreadLocal<Short> lockSet = ThreadLocal.withInitial( + () -> Short.valueOf((short)0)); + + + /** + * Creates new OzoneManagerLock instance. + * @param conf Configuration object + */ + public OzoneManagerLock(Configuration conf) { + manager = new LockManager<>(conf); + } + + /** + * Acquire lock on resource. + * + * For S3_Bucket, VOLUME, BUCKET type resource, same thread acquiring lock + * again is allowed. + * + * For USER, PREFIX, S3_SECRET type resource, same thread acquiring lock + * again is not allowed. + * + * Special Note for UserLock: Single thread can acquire single user lock/ + * multi user lock. But not both at the same time. + * @param resourceName - Resource name on which user want to acquire lock. + * @param resource - Type of the resource. + */ + public void acquireLock(String resourceName, Resource resource) { + if (!resource.canLock(lockSet.get())) { + String errorMessage = getErrorMessage(resource); + LOG.error(errorMessage); + throw new RuntimeException(errorMessage); + } else { + manager.lock(resourceName); + lockSet.set(resource.setLock(lockSet.get())); + } + } + + private String getErrorMessage(Resource resource) { + return "Thread '" + Thread.currentThread().getName() + "' cannot " + + "acquire " + resource.name + " lock while holding " + + getCurrentLocks().toString() + " lock(s)."; + + } + + private List<String> getCurrentLocks() { + List<String> currentLocks = new ArrayList<>(); + int i=0; + short lockSetVal = lockSet.get(); + for (Resource value : Resource.values()) { + if ((lockSetVal & value.setMask) == value.setMask) { + currentLocks.add(value.name); + } + } + return currentLocks; + } + + /** + * Acquire lock on multiple users. + * @param oldUserResource + * @param newUserResource + */ + public void acquireMultiUserLock(String oldUserResource, + String newUserResource) { + Resource resource = Resource.USER; + if (!resource.canLock(lockSet.get())) { + String errorMessage = getErrorMessage(resource); + LOG.error(errorMessage); + throw new RuntimeException(errorMessage); + } else { + int compare = newUserResource.compareTo(oldUserResource); + if (compare < 0) { + manager.lock(newUserResource); + try { + manager.lock(oldUserResource); + } catch (Exception ex) { + // We got an exception acquiring 2nd user lock. Release already + // acquired user lock, and throw exception to the user. + manager.unlock(oldUserResource); + throw ex; + } + } else if (compare > 0) { + // If this locking fails, we throw exception to user. + manager.lock(oldUserResource); + try { + manager.lock(newUserResource); + } catch (Exception ex) { + // We got an exception acquiring 2nd user lock. Release already + // acquired user lock, and throw exception to the user. + manager.unlock(oldUserResource); + throw ex; + } + } else { + // both users are equal. + manager.lock(oldUserResource); + } + lockSet.set(resource.setLock(lockSet.get())); + } + } + + /** + * Acquire lock on multiple users. + * @param oldUserResource + * @param newUserResource + */ + public void releaseMultiUserLock(String oldUserResource, + String newUserResource) { + Resource resource = Resource.USER; + int compare = newUserResource.compareTo(oldUserResource); + if (compare < 0) { + manager.unlock(newUserResource); + manager.unlock(oldUserResource); + } else if (compare > 0) { + manager.unlock(oldUserResource); + manager.unlock(newUserResource); + } else { + // both users are equal. + manager.unlock(oldUserResource); + } + lockSet.set(resource.clearLock(lockSet.get())); + } + + + public void releaseLock(String resourceName, Resource resource) { + + // TODO: Not checking release of higher order level lock happened while + // releasing lower order level lock, as for that we need counter for + // locks, as some locks support acquiring lock again. + manager.unlock(resourceName); + // clear lock + lockSet.set(resource.clearLock(lockSet.get())); + + } + + /** + * Resource defined in Ozone. + */ + public enum Resource { + // For S3 Bucket need to allow only for S3, that should be means only 1. + S3_BUCKET((byte) 0, "S3_BUCKET"), // = 1 + + // For volume need to allow both s3 bucket and volume. 01 + 10 = 11 (3) + VOLUME((byte) 1, "VOLUME"), // = 2 + + // For bucket we need to allow both s3 bucket, volume and bucket. Which + // is equal to 100 + 010 + 001 = 111 = 4 + 2 + 1 = 7 + BUCKET((byte) 2, "BUCKET"), // = 4 + + // For user we need to allow s3 bucket, volume, bucket and user lock. + // Which is 8 4 + 2 + 1 = 15 + USER((byte) 3, "USER"), // 15 + + S3_SECRET((byte) 4, "S3_SECRET"), // 31 + PREFIX((byte) 5, "PREFIX"); //63 + + // level of the resource + private byte lockLevel; + + // This will tell the value, till which we can allow locking. + private short mask; + + // This value will help during setLock, and also will tell whether we can + // re-acquire lock or not. + private short setMask; + + // Name of the resource. + private String name; + + Resource(byte pos, String name) { + this.lockLevel = pos; + for (int x = 0; x < lockLevel + 1; x++) { + this.mask += (short) Math.pow(2, x); Review comment: Done ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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