| /** |
| * 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.hcatalog.hbase.snapshot; |
| |
| import java.io.IOException; |
| import java.nio.charset.Charset; |
| |
| import org.apache.hcatalog.hbase.snapshot.lock.LockListener; |
| import org.apache.hcatalog.hbase.snapshot.lock.WriteLock; |
| import org.apache.zookeeper.KeeperException; |
| import org.apache.zookeeper.ZooDefs.Ids; |
| import org.apache.zookeeper.ZooKeeper; |
| import org.apache.zookeeper.data.Stat; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| |
| /** |
| * This class generates revision id's for transactions. |
| */ |
| class IDGenerator implements LockListener { |
| |
| private ZooKeeper zookeeper; |
| private String zNodeDataLoc; |
| private String zNodeLockBasePath; |
| private long id; |
| private static final Logger LOG = LoggerFactory.getLogger(IDGenerator.class); |
| |
| IDGenerator(ZooKeeper zookeeper, String tableName, String idGenNode) |
| throws IOException { |
| this.zookeeper = zookeeper; |
| this.zNodeDataLoc = idGenNode; |
| this.zNodeLockBasePath = PathUtil.getLockManagementNode(idGenNode); |
| } |
| |
| /** |
| * This method obtains a revision id for a transaction. |
| * |
| * @return revision ID |
| * @throws IOException |
| */ |
| public long obtainID() throws IOException { |
| WriteLock wLock = new WriteLock(zookeeper, zNodeLockBasePath, Ids.OPEN_ACL_UNSAFE); |
| wLock.setLockListener(this); |
| try { |
| boolean lockGrabbed = wLock.lock(); |
| if (lockGrabbed == false) { |
| //TO DO : Let this request queue up and try obtaining lock. |
| throw new IOException("Unable to obtain lock to obtain id."); |
| } else { |
| id = incrementAndReadCounter(); |
| } |
| } catch (KeeperException e) { |
| LOG.warn("Exception while obtaining lock for ID.", e); |
| throw new IOException("Exception while obtaining lock for ID.", e); |
| } catch (InterruptedException e) { |
| LOG.warn("Exception while obtaining lock for ID.", e); |
| throw new IOException("Exception while obtaining lock for ID.", e); |
| } finally { |
| wLock.unlock(); |
| } |
| return id; |
| } |
| |
| /** |
| * This method reads the latest revision ID that has been used. The ID |
| * returned by this method cannot be used for transaction. |
| * @return revision ID |
| * @throws IOException |
| */ |
| public long readID() throws IOException { |
| long curId; |
| try { |
| Stat stat = new Stat(); |
| byte[] data = zookeeper.getData(this.zNodeDataLoc, false, stat); |
| curId = Long.parseLong(new String(data, Charset.forName("UTF-8"))); |
| } catch (KeeperException e) { |
| LOG.warn("Exception while reading current revision id.", e); |
| throw new IOException("Exception while reading current revision id.", e); |
| } catch (InterruptedException e) { |
| LOG.warn("Exception while reading current revision id.", e); |
| throw new IOException("Exception while reading current revision id.", e); |
| } |
| |
| return curId; |
| } |
| |
| |
| private long incrementAndReadCounter() throws IOException { |
| |
| long curId, usedId; |
| try { |
| Stat stat = new Stat(); |
| byte[] data = zookeeper.getData(this.zNodeDataLoc, false, stat); |
| usedId = Long.parseLong((new String(data, Charset.forName("UTF-8")))); |
| curId = usedId + 1; |
| String lastUsedID = String.valueOf(curId); |
| zookeeper.setData(this.zNodeDataLoc, lastUsedID.getBytes(Charset.forName("UTF-8")), -1); |
| |
| } catch (KeeperException e) { |
| LOG.warn("Exception while incrementing revision id.", e); |
| throw new IOException("Exception while incrementing revision id. ", e); |
| } catch (InterruptedException e) { |
| LOG.warn("Exception while incrementing revision id.", e); |
| throw new IOException("Exception while incrementing revision id. ", e); |
| } |
| |
| return curId; |
| } |
| |
| /* |
| * @see org.apache.hcatalog.hbase.snapshot.lock.LockListener#lockAcquired() |
| */ |
| @Override |
| public void lockAcquired() { |
| |
| |
| } |
| |
| /* |
| * @see org.apache.hcatalog.hbase.snapshot.lock.LockListener#lockReleased() |
| */ |
| @Override |
| public void lockReleased() { |
| |
| } |
| |
| |
| } |