|
|
@@ -0,0 +1,161 @@
|
|
|
+/**
|
|
|
+ * 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.contrib.bkjournal;
|
|
|
+
|
|
|
+import java.io.IOException;
|
|
|
+import java.net.InetAddress;
|
|
|
+
|
|
|
+import org.apache.commons.logging.Log;
|
|
|
+import org.apache.commons.logging.LogFactory;
|
|
|
+import org.apache.zookeeper.CreateMode;
|
|
|
+import org.apache.zookeeper.KeeperException;
|
|
|
+import org.apache.zookeeper.ZooKeeper;
|
|
|
+import org.apache.zookeeper.KeeperException.NodeExistsException;
|
|
|
+import org.apache.zookeeper.ZooDefs.Ids;
|
|
|
+import org.apache.zookeeper.data.Stat;
|
|
|
+
|
|
|
+/**
|
|
|
+ * Distributed write permission lock, using ZooKeeper. Read the version number
|
|
|
+ * and return the current inprogress node path available in CurrentInprogress
|
|
|
+ * path. If it exist, caller can treat that some other client already operating
|
|
|
+ * on it. Then caller can take action. If there is no inprogress node exist,
|
|
|
+ * then caller can treat that there is no client operating on it. Later same
|
|
|
+ * caller should update the his newly created inprogress node path. At this
|
|
|
+ * point, if some other activities done on this node, version number might
|
|
|
+ * change, so update will fail. So, this read, update api will ensure that there
|
|
|
+ * is only node can continue further after checking with CurrentInprogress.
|
|
|
+ */
|
|
|
+
|
|
|
+class CurrentInprogress {
|
|
|
+ private static final String CONTENT_DELIMITER = ",";
|
|
|
+
|
|
|
+ static final Log LOG = LogFactory.getLog(CurrentInprogress.class);
|
|
|
+
|
|
|
+ private final ZooKeeper zkc;
|
|
|
+ private final String currentInprogressNode;
|
|
|
+ private volatile int versionNumberForPermission = -1;
|
|
|
+ private static final int CURRENT_INPROGRESS_LAYOUT_VERSION = -1;
|
|
|
+ private final String hostName = InetAddress.getLocalHost().toString();
|
|
|
+
|
|
|
+ CurrentInprogress(ZooKeeper zkc, String lockpath) throws IOException {
|
|
|
+ this.currentInprogressNode = lockpath;
|
|
|
+ this.zkc = zkc;
|
|
|
+ try {
|
|
|
+ Stat isCurrentInprogressNodeExists = zkc.exists(lockpath, false);
|
|
|
+ if (isCurrentInprogressNodeExists == null) {
|
|
|
+ try {
|
|
|
+ zkc.create(lockpath, null, Ids.OPEN_ACL_UNSAFE,
|
|
|
+ CreateMode.PERSISTENT);
|
|
|
+ } catch (NodeExistsException e) {
|
|
|
+ // Node might created by other process at the same time. Ignore it.
|
|
|
+ if (LOG.isDebugEnabled()) {
|
|
|
+ LOG.debug(lockpath + " already created by other process.", e);
|
|
|
+ }
|
|
|
+ }
|
|
|
+ }
|
|
|
+ } catch (Exception e) {
|
|
|
+ throw new IOException("Exception accessing Zookeeper", e);
|
|
|
+ }
|
|
|
+ }
|
|
|
+
|
|
|
+ /**
|
|
|
+ * Update the path with prepending version number and hostname
|
|
|
+ *
|
|
|
+ * @param path
|
|
|
+ * - to be updated in zookeeper
|
|
|
+ * @throws IOException
|
|
|
+ */
|
|
|
+ void update(String path) throws IOException {
|
|
|
+ String content = CURRENT_INPROGRESS_LAYOUT_VERSION
|
|
|
+ + CONTENT_DELIMITER + hostName + CONTENT_DELIMITER + path;
|
|
|
+ try {
|
|
|
+ zkc.setData(this.currentInprogressNode, content.getBytes(),
|
|
|
+ this.versionNumberForPermission);
|
|
|
+ } catch (KeeperException e) {
|
|
|
+ throw new IOException("Exception when setting the data "
|
|
|
+ + "[layout version number,hostname,inprogressNode path]= [" + content
|
|
|
+ + "] to CurrentInprogress. ", e);
|
|
|
+ } catch (InterruptedException e) {
|
|
|
+ throw new IOException("Interrupted while setting the data "
|
|
|
+ + "[layout version number,hostname,inprogressNode path]= [" + content
|
|
|
+ + "] to CurrentInprogress", e);
|
|
|
+ }
|
|
|
+ LOG.info("Updated data[layout version number,hostname,inprogressNode path]"
|
|
|
+ + "= [" + content + "] to CurrentInprogress");
|
|
|
+ }
|
|
|
+
|
|
|
+ /**
|
|
|
+ * Read the CurrentInprogress node data from Zookeeper and also get the znode
|
|
|
+ * version number. Return the 3rd field from the data. i.e saved path with
|
|
|
+ * #update api
|
|
|
+ *
|
|
|
+ * @return available inprogress node path. returns null if not available.
|
|
|
+ * @throws IOException
|
|
|
+ */
|
|
|
+ String read() throws IOException {
|
|
|
+ Stat stat = new Stat();
|
|
|
+ byte[] data = null;
|
|
|
+ try {
|
|
|
+ data = zkc.getData(this.currentInprogressNode, false, stat);
|
|
|
+ } catch (KeeperException e) {
|
|
|
+ throw new IOException("Exception while reading the data from "
|
|
|
+ + currentInprogressNode, e);
|
|
|
+ } catch (InterruptedException e) {
|
|
|
+ throw new IOException("Interrupted while reading data from "
|
|
|
+ + currentInprogressNode, e);
|
|
|
+ }
|
|
|
+ this.versionNumberForPermission = stat.getVersion();
|
|
|
+ if (data != null) {
|
|
|
+ String stringData = new String(data);
|
|
|
+ LOG.info("Read data[layout version number,hostname,inprogressNode path]"
|
|
|
+ + "= [" + stringData + "] from CurrentInprogress");
|
|
|
+ String[] contents = stringData.split(CONTENT_DELIMITER);
|
|
|
+ assert contents.length == 3 : "As per the current data format, "
|
|
|
+ + "CurrentInprogress node data should contain 3 fields. "
|
|
|
+ + "i.e layout version number,hostname,inprogressNode path";
|
|
|
+ String layoutVersion = contents[0];
|
|
|
+ if (Long.valueOf(layoutVersion) > CURRENT_INPROGRESS_LAYOUT_VERSION) {
|
|
|
+ throw new IOException(
|
|
|
+ "Supported layout version of CurrentInprogress node is : "
|
|
|
+ + CURRENT_INPROGRESS_LAYOUT_VERSION
|
|
|
+ + " . Layout version of CurrentInprogress node in ZK is : "
|
|
|
+ + layoutVersion);
|
|
|
+ }
|
|
|
+ String inprogressNodePath = contents[2];
|
|
|
+ return inprogressNodePath;
|
|
|
+ } else {
|
|
|
+ LOG.info("No data available in CurrentInprogress");
|
|
|
+ }
|
|
|
+ return null;
|
|
|
+ }
|
|
|
+
|
|
|
+ /** Clear the CurrentInprogress node data */
|
|
|
+ void clear() throws IOException {
|
|
|
+ try {
|
|
|
+ zkc.setData(this.currentInprogressNode, null, versionNumberForPermission);
|
|
|
+ } catch (KeeperException e) {
|
|
|
+ throw new IOException(
|
|
|
+ "Exception when setting the data to CurrentInprogress node", e);
|
|
|
+ } catch (InterruptedException e) {
|
|
|
+ throw new IOException(
|
|
|
+ "Interrupted when setting the data to CurrentInprogress node", e);
|
|
|
+ }
|
|
|
+ LOG.info("Cleared the data from CurrentInprogress");
|
|
|
+ }
|
|
|
+
|
|
|
+}
|
Uma Maheswara Rao G