Github user tillrohrmann commented on a diff in the pull request:
https://github.com/apache/flink/pull/1153#discussion_r41126510
--- 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/<job-id> 1 [persistent]
+ * .
+ * .
+ * .
+ * +----O /flink/jobgraphs/<job-id> 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");
--- End diff --
`this.client = checkNotNull(....)`.
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