diff options
Diffstat (limited to 'policy-core/src/main/java/org/onap/policy/drools/core/lock/SimpleLockManager.java')
| -rw-r--r-- | policy-core/src/main/java/org/onap/policy/drools/core/lock/SimpleLockManager.java | 168 |
1 files changed, 168 insertions, 0 deletions
diff --git a/policy-core/src/main/java/org/onap/policy/drools/core/lock/SimpleLockManager.java b/policy-core/src/main/java/org/onap/policy/drools/core/lock/SimpleLockManager.java new file mode 100644 index 00000000..14cffaab --- /dev/null +++ b/policy-core/src/main/java/org/onap/policy/drools/core/lock/SimpleLockManager.java @@ -0,0 +1,168 @@ +/* + * ============LICENSE_START======================================================= + * ONAP + * ================================================================================ + * Copyright (C) 2018 AT&T Intellectual Property. All rights reserved. + * ================================================================================ + * Licensed 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. + * ============LICENSE_END========================================================= + */ + +package org.onap.policy.drools.core.lock; + +import static org.onap.policy.drools.core.lock.LockRequestFuture.MSG_NULL_OWNER; +import static org.onap.policy.drools.core.lock.LockRequestFuture.MSG_NULL_RESOURCE_ID; +import static org.onap.policy.drools.core.lock.LockRequestFuture.makeNullArgException; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.Future; +import org.onap.policy.drools.core.lock.PolicyResourceLockFeatureAPI.Callback; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * Simple lock manager. Callbacks are ignored. Does not redirect to lock feature + * implementers. + */ +public class SimpleLockManager { + + protected static Logger logger = LoggerFactory.getLogger(SimpleLockManager.class); + + /** + * Maps a resource to the owner that holds the lock on it. + */ + private ConcurrentHashMap<String, String> resource2owner = new ConcurrentHashMap<>(); + + /** + * + */ + public SimpleLockManager() { + super(); + } + + // TODO: for ease of use by clients, should we always invoke the callback, even though + // this is synchronous? + + /** + * Attempts to lock a resource. This method ignores the callback and always returns a + * {@link CompletedLockRequest}. + * + * @param resourceId + * @param owner + * @param callback function to invoke, if the requester wishes to wait for the lock to + * be acquired, {@code null} to provide immediate replies + * @return a future for the lock request. The future will be in one of three states: + * <dl> + * <dt>isDone()=true and get()=true</dt> + * <dd>the lock has been acquired; the callback may or may not have been + * invoked</dd> + * <dt>isDone()=true and get()=false</dt> + * <dd>the lock request has been denied; the callback may or may not have been + * invoked</dd> + * <dt>isDone()=false</dt> + * <dd>the lock was not immediately available and a callback was provided. The + * callback will be invoked once the lock is acquired (or denied). In this + * case, the future may be used to cancel the request</dd> + * </dl> + * @throws IllegalArgumentException if the resourceId or owner is {@code null} + * @throws IllegalStateException if the owner already holds the lock or is already in + * the queue to get the lock + */ + public Future<Boolean> lock(String resourceId, String owner, Callback callback) { + + if (resourceId == null) { + throw makeNullArgException(MSG_NULL_RESOURCE_ID); + } + + if (owner == null) { + throw makeNullArgException(MSG_NULL_OWNER); + } + + boolean locked = (resource2owner.putIfAbsent(resourceId, owner) == null); + + if (!locked && owner.equals(resource2owner.get(resourceId))) { + throw new IllegalStateException("lock for resource " + resourceId + " already owned by " + owner); + } + + logger.info("lock {} for resource {} owner {}", locked, resourceId, owner); + + return new LockRequestFuture(resourceId, owner, locked); + } + + /** + * Unlocks a resource. + * + * @param resourceId + * @param owner + * @return {@code true} if unlocked, {@code false} if the given owner does not + * currently hold a lock on the resource + * @throws IllegalArgumentException if the resourceId or owner is {@code null} + */ + public boolean unlock(String resourceId, String owner) { + if (resourceId == null) { + throw makeNullArgException(MSG_NULL_RESOURCE_ID); + } + + if (owner == null) { + throw makeNullArgException(MSG_NULL_OWNER); + } + + boolean unlocked = resource2owner.remove(resourceId, owner); + logger.info("unlock resource {} owner {} = {}", resourceId, owner, unlocked); + + return unlocked; + } + + /** + * Determines if a resource is locked by anyone. + * + * @param resourceId + * @return {@code true} if the resource is locked, {@code false} otherwise + * @throws IllegalArgumentException if the resourceId is {@code null} + */ + public boolean isLocked(String resourceId) { + + if (resourceId == null) { + throw makeNullArgException(MSG_NULL_RESOURCE_ID); + } + + boolean locked = resource2owner.containsKey(resourceId); + + logger.debug("resource {} isLocked = {}", resourceId, locked); + + return locked; + } + + /** + * Determines if a resource is locked by a particular owner. + * + * @param resourceId + * @param owner + * @return {@code true} if the resource is locked, {@code false} otherwise + * @throws IllegalArgumentException if the resourceId or owner is {@code null} + */ + public boolean isLockedBy(String resourceId, String owner) { + + if (resourceId == null) { + throw makeNullArgException(MSG_NULL_RESOURCE_ID); + } + + if (owner == null) { + throw makeNullArgException(MSG_NULL_OWNER); + } + + boolean locked = owner.equals(resource2owner.get(resourceId)); + logger.debug("resource {} isLockedBy {} = {}", resourceId, owner, locked); + + return locked; + } +} |