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From uce <...@git.apache.org>
Subject [GitHub] flink pull request: [FLINK-2354] Add job graph and checkpoint reco...
Date Mon, 05 Oct 2015 14:47:43 GMT
Github user uce commented on a diff in the pull request:

    https://github.com/apache/flink/pull/1153#discussion_r41152148
  
    --- Diff: flink-runtime/src/main/java/org/apache/flink/runtime/jobmanager/ZooKeeperSubmittedJobGraphs.java
---
    @@ -0,0 +1,356 @@
    +/*
    + * 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.flink.runtime.jobmanager;
    +
    +import org.apache.curator.framework.CuratorFramework;
    +import org.apache.curator.framework.recipes.cache.PathChildrenCache;
    +import org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent;
    +import org.apache.curator.framework.recipes.cache.PathChildrenCacheListener;
    +import org.apache.curator.utils.ZKPaths;
    +import org.apache.flink.api.common.JobID;
    +import org.apache.flink.runtime.state.StateHandle;
    +import org.apache.flink.runtime.state.StateHandleProvider;
    +import org.apache.flink.runtime.zookeeper.ZooKeeperStateHandle;
    +import org.apache.flink.runtime.zookeeper.ZooKeeperStateHandleStore;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +
    +import java.util.ArrayList;
    +import java.util.Collections;
    +import java.util.ConcurrentModificationException;
    +import java.util.HashSet;
    +import java.util.List;
    +import java.util.Set;
    +
    +import static com.google.common.base.Preconditions.checkNotNull;
    +import static com.google.common.base.Preconditions.checkState;
    +
    +/**
    + * {@link SubmittedJobGraph} instances for JobManagers running in {@link RecoveryMode#ZOOKEEPER}.
    + *
    + * <p>Each job graph creates ZNode:
    + * <pre>
    + * +----O /flink/jobgraphs/&lt;job-id&gt; 1 [persistent]
    + * .
    + * .
    + * .
    + * +----O /flink/jobgraphs/&lt;job-id&gt; N [persistent]
    + * </pre>
    + *
    + * <p>The root path is watched to detect concurrent modifications in corner situations
where
    + * multiple instances operate concurrently. The job manager acts as a {@link SubmittedJobGraphListener}
    + * to react to such situations.
    + */
    +public class ZooKeeperSubmittedJobGraphs implements SubmittedJobGraphs {
    +
    +	private static final Logger LOG = LoggerFactory.getLogger(ZooKeeperSubmittedJobGraphs.class);
    +
    +	/** Lock to synchronize with the {@link SubmittedJobGraphListener}. */
    +	private final Object cacheLock = new Object();
    +
    +	/** Client (not a namespace facade) */
    +	private final CuratorFramework client;
    +
    +	/** The set of IDs of all added job graphs. */
    +	private final Set<JobID> addedJobGraphs = new HashSet<>();
    +
    +	/** Completed checkpoints in ZooKeeper */
    +	private final ZooKeeperStateHandleStore<SubmittedJobGraph> jobGraphsInZooKeeper;
    +
    +	/**
    +	 * Cache to monitor all children. This is used to detect races with other instances
working
    +	 * on the same state.
    +	 */
    +	private final PathChildrenCache pathCache;
    +
    +	/** The external listener to be notified on races. */
    +	private SubmittedJobGraphListener jobGraphListener;
    +
    +	/** Flag indicating whether this instance is running. */
    +	private boolean isRunning;
    +
    +	public ZooKeeperSubmittedJobGraphs(
    +			CuratorFramework client,
    +			String currentJobsPath,
    +			StateHandleProvider<SubmittedJobGraph> stateHandleProvider) throws Exception
{
    +
    +		checkNotNull(client, "Curator client");
    +		checkNotNull(currentJobsPath, "Current jobs path");
    +		checkNotNull(stateHandleProvider, "State handle provider");
    +
    +		// Keep a reference to the original client and not the namespace facade. The namespace
    +		// facade cannot be closed.
    +		this.client = client;
    +
    +		// Ensure that the job graphs path exists
    +		client.newNamespaceAwareEnsurePath(currentJobsPath)
    +				.ensure(client.getZookeeperClient());
    +
    +		// All operations will have the path as root
    +		client = client.usingNamespace(client.getNamespace() + currentJobsPath);
    +
    +		this.jobGraphsInZooKeeper = new ZooKeeperStateHandleStore<>(client, stateHandleProvider);
    +
    +		this.pathCache = new PathChildrenCache(client, "/", false);
    +		pathCache.getListenable().addListener(new SubmittedJobGraphsPathCacheListener());
    +	}
    +
    +	@Override
    +	public void start(SubmittedJobGraphListener jobGraphListener) throws Exception {
    +		synchronized (cacheLock) {
    +			if (!isRunning) {
    +				this.jobGraphListener = jobGraphListener;
    +
    +				pathCache.start();
    +
    +				isRunning = true;
    +			}
    +		}
    +	}
    +
    +	@Override
    +	public void stop() throws Exception {
    +		synchronized (cacheLock) {
    +			if (isRunning) {
    +				jobGraphListener = null;
    +
    +				pathCache.close();
    +
    +				client.close();
    +
    +				isRunning = false;
    +			}
    +		}
    +	}
    +
    +	@Override
    +	public List<SubmittedJobGraph> recoverJobGraphs() throws Exception {
    +		synchronized (cacheLock) {
    +			verifyIsRunning();
    +
    +			List<ZooKeeperStateHandle<SubmittedJobGraph>> submitted;
    +
    +			while (true) {
    +				try {
    +					submitted = jobGraphsInZooKeeper.getAll();
    +					break;
    +				}
    +				catch (ConcurrentModificationException e) {
    +					LOG.warn("Concurrent modification while reading from ZooKeeper. Retrying.");
    +				}
    +			}
    +
    +			if (submitted.size() != 0) {
    +				List<SubmittedJobGraph> jobGraphs = new ArrayList<>(submitted.size());
    +
    +				for (ZooKeeperStateHandle<SubmittedJobGraph> jobStateHandle : submitted) {
    +					SubmittedJobGraph jobGraph = jobStateHandle
    +							.getStateHandle()
    +							.getState(ClassLoader.getSystemClassLoader());
    +
    +					addedJobGraphs.add(jobGraph.getJobId());
    +
    +					jobGraphs.add(jobGraph);
    +				}
    +
    +				LOG.info("Recovered {} job graphs: {}.", jobGraphs.size(), jobGraphs);
    +				return jobGraphs;
    +			}
    +			else {
    +				LOG.info("No job graph to recover.");
    +				return Collections.emptyList();
    +			}
    +		}
    +	}
    +
    +	@Override
    +	public SubmittedJobGraph recoverJobGraph(JobID jobId) throws Exception {
    +		checkNotNull(jobId, "Job ID");
    +		String path = getPathForJob(jobId);
    +
    +		synchronized (cacheLock) {
    +			verifyIsRunning();
    +
    +			StateHandle<SubmittedJobGraph> jobStateHandle = jobGraphsInZooKeeper.get(path);
    +
    +			SubmittedJobGraph jobGraph = jobStateHandle
    +					.getState(ClassLoader.getSystemClassLoader());
    +
    +			addedJobGraphs.add(jobGraph.getJobId());
    +
    +			LOG.info("Recovered {}.", jobGraph);
    +			return jobGraph;
    +		}
    +	}
    +
    +	@Override
    +	public void putJobGraph(SubmittedJobGraph jobGraph) throws Exception {
    +		checkNotNull(jobGraph, "Job graph");
    +		String path = getPathForJob(jobGraph.getJobId());
    +
    +		synchronized (cacheLock) {
    +			verifyIsRunning();
    +
    +			int currentVersion = jobGraphsInZooKeeper.exists(path);
    +
    +			if (currentVersion == -1) {
    +				jobGraphsInZooKeeper.add(path, jobGraph);
    +				LOG.info("Added {} to ZooKeeper.", jobGraph);
    +			}
    +			else if (addedJobGraphs.contains(jobGraph.getJobId())) {
    +				jobGraphsInZooKeeper.replace(path, currentVersion, jobGraph);
    +				LOG.info("Updated {} in ZooKeeper.", jobGraph);
    +			}
    +			else {
    +				throw new IllegalStateException("Oh, no. Trying to update a graph you didn't " +
    +						"#getAllSubmittedJobGraphs() or #putJobGraph() yourself before.");
    +			}
    +
    +			addedJobGraphs.add(jobGraph.getJobId());
    +		}
    +	}
    +
    +	@Override
    +	public void removeJobGraph(JobID jobId) throws Exception {
    +		checkNotNull(jobId, "Job ID");
    +		String path = getPathForJob(jobId);
    +
    +		synchronized (cacheLock) {
    +			if (addedJobGraphs.contains(jobId)) {
    +				jobGraphsInZooKeeper.discard(path);
    +
    +				addedJobGraphs.remove(jobId);
    +				LOG.info("Removed job graph {} from ZooKeeper.", jobId);
    +			}
    +		}
    +	}
    +
    +	/**
    +	 * Monitors ZooKeeper for changes.
    +	 *
    +	 * <p>Detects modifications from other job managers in corner situations. The
event
    +	 * notifications fire for changes from this job manager as well.
    +	 */
    +	private final class SubmittedJobGraphsPathCacheListener implements PathChildrenCacheListener
{
    +
    +		@Override
    +		public void childEvent(CuratorFramework client, PathChildrenCacheEvent event)
    +				throws Exception {
    +
    +			if (LOG.isDebugEnabled()) {
    +				if (event.getData() != null) {
    +					LOG.debug("Received {} event (path: {})", event.getType(), event.getData().getPath());
    +				}
    +				else {
    +					LOG.debug("Received {} event", event.getType());
    +				}
    +			}
    +
    +			synchronized (cacheLock) {
    +				switch (event.getType()) {
    +					case CHILD_ADDED:
    +						try {
    +							JobID jobId = fromEvent(event);
    +							if (jobGraphListener != null && !addedJobGraphs.contains(jobId)) {
    +								try {
    +									// Whoa! This has been added by someone else. Or we were fast
    +									// to remove it (false positive).
    +									jobGraphListener.onAddedJobGraph(jobId);
    +								}
    +								catch (Throwable t) {
    +									LOG.error("Error in callback", t);
    +								}
    +							}
    +						}
    +						catch (Exception e) {
    +							LOG.error("Error in SubmittedJobGraphsPathCacheListener", e);
    +						}
    +
    +						break;
    +
    +					case CHILD_UPDATED:
    +						// TODO What to do if someone overwrites one of our job graphs? And how
    +						// to tell whose it is? Is the update-time check enough to prevent these
    +						// problematic situations.
    --- End diff --
    
    +1


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