001/* 002 * (C) Copyright 2017 Nuxeo (http://nuxeo.com/) and others. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * http://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 * 016 * Contributors: 017 * Funsho David 018 * 019 */ 020 021package org.nuxeo.ecm.core.api; 022 023import org.nuxeo.runtime.api.Framework; 024import org.nuxeo.runtime.kv.KeyValueService; 025import org.nuxeo.runtime.kv.KeyValueStore; 026import org.nuxeo.runtime.transaction.TransactionHelper; 027 028import java.util.function.Supplier; 029 030/** 031 * Utilities to work with locks 032 * 033 * @since 9.3 034 */ 035public class LockHelper { 036 037 public static final String DOCUMENT_LOCK = "document-lock"; 038 039 public static final String LOCK = "lock"; 040 041 public static final int NB_TRY = 3; 042 043 public static final int SLEEP_DURATION = 1000; 044 045 private LockHelper() { 046 } 047 048 /** 049 * Runs a {@link Runnable} atomically, in a cluster-wide critical section. 050 * 051 * @param key the key used to determine atomicity 052 * @param runnable the runnable 053 */ 054 public static void doAtomically(String key, Runnable runnable) throws ConcurrentUpdateException { 055 doAtomically(key, () -> { 056 runnable.run(); 057 return null; 058 }); 059 } 060 061 /** 062 * Runs a {@link Supplier} atomically, in a cluster-wide critical section. 063 * 064 * @param key the key used to determine atomicity 065 * @param supplier the supplier 066 * @return the result of the function 067 */ 068 public static <R> R doAtomically(String key, Supplier<R> supplier) throws ConcurrentUpdateException { 069 070 KeyValueStore kvStore = Framework.getService(KeyValueService.class).getKeyValueStore(DOCUMENT_LOCK); 071 072 try { 073 if (tryLock(key, kvStore)) { 074 try { 075 TransactionHelper.commitOrRollbackTransaction(); 076 TransactionHelper.startTransaction(); 077 078 return supplier.get(); 079 } finally { 080 try { 081 TransactionHelper.commitOrRollbackTransaction(); 082 TransactionHelper.startTransaction(); 083 } finally { 084 unlock(key, kvStore); 085 } 086 } 087 } else { 088 throw new ConcurrentUpdateException("Failed to acquire the lock on key " + key); 089 } 090 } catch (InterruptedException e) { 091 Thread.currentThread().interrupt(); 092 throw new NuxeoException(e); 093 } 094 } 095 096 protected static boolean tryLock(String key, KeyValueStore kvStore) throws InterruptedException { 097 // Try to acquire the lock and fail if it takes too long 098 long sleepDuration = SLEEP_DURATION; 099 for (int i = 0; i < NB_TRY; i++) { 100 if (kvStore.compareAndSet(key, null, LOCK)) { 101 return true; 102 } 103 Thread.sleep(sleepDuration); 104 sleepDuration *= 2; 105 } 106 return false; 107 } 108 109 protected static void unlock(String key, KeyValueStore kvStore) { 110 kvStore.put(key, (String) null); 111 } 112 113}