Java tutorial
/* * 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.accumulo.server.master.tableOps; import java.math.BigInteger; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock; import org.apache.accumulo.core.Constants; import org.apache.accumulo.core.client.Instance; import org.apache.accumulo.core.client.impl.Tables; import org.apache.accumulo.core.client.impl.thrift.TableOperation; import org.apache.accumulo.core.client.impl.thrift.TableOperationExceptionType; import org.apache.accumulo.core.client.impl.thrift.ThriftTableOperationException; import org.apache.accumulo.core.zookeeper.ZooUtil; import org.apache.accumulo.fate.zookeeper.DistributedReadWriteLock; import org.apache.accumulo.fate.zookeeper.IZooReaderWriter; import org.apache.accumulo.fate.zookeeper.IZooReaderWriter.Mutator; import org.apache.accumulo.fate.zookeeper.ZooReservation; import org.apache.accumulo.server.client.HdfsZooInstance; import org.apache.accumulo.server.zookeeper.ZooQueueLock; import org.apache.accumulo.server.zookeeper.ZooReaderWriter; import org.apache.commons.codec.binary.Base64; import org.apache.log4j.Logger; import org.apache.zookeeper.KeeperException; public class Utils { static void checkTableDoesNotExist(Instance instance, String tableName, String tableId, TableOperation operation) throws ThriftTableOperationException { String id = Tables.getNameToIdMap(instance).get(tableName); if (id != null && !id.equals(tableId)) throw new ThriftTableOperationException(null, tableName, operation, TableOperationExceptionType.EXISTS, null); } static String getNextTableId(String tableName, Instance instance) throws ThriftTableOperationException { String tableId = null; try { IZooReaderWriter zoo = ZooReaderWriter.getRetryingInstance(); final String ntp = ZooUtil.getRoot(instance) + Constants.ZTABLES; byte[] nid = zoo.mutate(ntp, "0".getBytes(), ZooUtil.PUBLIC, new Mutator() { @Override public byte[] mutate(byte[] currentValue) throws Exception { BigInteger nextId = new BigInteger(new String(currentValue), Character.MAX_RADIX); nextId = nextId.add(BigInteger.ONE); return nextId.toString(Character.MAX_RADIX).getBytes(); } }); return new String(nid); } catch (Exception e1) { Logger.getLogger(CreateTable.class).error("Failed to assign tableId to " + tableName, e1); throw new ThriftTableOperationException(tableId, tableName, TableOperation.CREATE, TableOperationExceptionType.OTHER, e1.getMessage()); } } static final Lock tableNameLock = new ReentrantLock(); static final Lock idLock = new ReentrantLock(); private static final Logger log = Logger.getLogger(Utils.class); public static long reserveTable(String tableId, long tid, boolean writeLock, boolean tableMustExist, TableOperation op) throws Exception { if (getLock(tableId, tid, writeLock).tryLock()) { if (tableMustExist) { Instance instance = HdfsZooInstance.getInstance(); IZooReaderWriter zk = ZooReaderWriter.getRetryingInstance(); if (!zk.exists(ZooUtil.getRoot(instance) + Constants.ZTABLES + "/" + tableId)) throw new ThriftTableOperationException(tableId, "", op, TableOperationExceptionType.NOTFOUND, "Table does not exists"); } log.info("table " + tableId + " (" + Long.toHexString(tid) + ") locked for " + (writeLock ? "write" : "read") + " operation: " + op); return 0; } else return 100; } public static void unreserveTable(String tableId, long tid, boolean writeLock) throws Exception { getLock(tableId, tid, writeLock).unlock(); log.info("table " + tableId + " (" + Long.toHexString(tid) + ") unlocked for " + (writeLock ? "write" : "read")); } public static long reserveHdfsDirectory(String directory, long tid) throws KeeperException, InterruptedException { Instance instance = HdfsZooInstance.getInstance(); String resvPath = ZooUtil.getRoot(instance) + Constants.ZHDFS_RESERVATIONS + "/" + new String(Base64.encodeBase64(directory.getBytes())); IZooReaderWriter zk = ZooReaderWriter.getRetryingInstance(); if (ZooReservation.attempt(zk, resvPath, String.format("%016x", tid), "")) { return 0; } else return 50; } public static void unreserveHdfsDirectory(String directory, long tid) throws KeeperException, InterruptedException { Instance instance = HdfsZooInstance.getInstance(); String resvPath = ZooUtil.getRoot(instance) + Constants.ZHDFS_RESERVATIONS + "/" + new String(Base64.encodeBase64(directory.getBytes())); ZooReservation.release(ZooReaderWriter.getRetryingInstance(), resvPath, String.format("%016x", tid)); } private static Lock getLock(String tableId, long tid, boolean writeLock) throws Exception { byte[] lockData = String.format("%016x", tid).getBytes(); ZooQueueLock qlock = new ZooQueueLock( ZooUtil.getRoot(HdfsZooInstance.getInstance()) + Constants.ZTABLE_LOCKS + "/" + tableId, false); Lock lock = DistributedReadWriteLock.recoverLock(qlock, lockData); if (lock == null) { DistributedReadWriteLock locker = new DistributedReadWriteLock(qlock, lockData); if (writeLock) lock = locker.writeLock(); else lock = locker.readLock(); } return lock; } public static Lock getReadLock(String tableId, long tid) throws Exception { return Utils.getLock(tableId, tid, false); } }