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https://issues.apache.org/jira/browse/FLINK-2976?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15045233#comment-15045233
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ASF GitHub Bot commented on FLINK-2976:
---------------------------------------
Github user tillrohrmann commented on a diff in the pull request:
https://github.com/apache/flink/pull/1434#discussion_r46845520
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/checkpoint/HeapStateStore.java
---
@@ -0,0 +1,84 @@
+/*
+ * 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.checkpoint;
+
+import java.io.Serializable;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+/**
+ * Java heap backed {@link StateStore}.
+ *
+ * @param <T> Type of state
+ */
+class HeapStateStore<T extends Serializable> implements StateStore<T> {
+
+ private final Map<String, T> stateMap = new HashMap<>();
+
+ private final AtomicInteger idCounter = new AtomicInteger();
+
+ @Override
+ public String putState(T state) throws Exception {
+ checkNotNull(state, "State");
+
+ String key = "jobmanager://savepoints/" +
idCounter.incrementAndGet();
--- End diff --
Why do we use an `AtomicInteger` here? Does this mean that `putState` will
be accessed concurrently? If this is the case, then `stateMap.put` is
problematic, since a `HashMap` is not thread safe.
> Save and load checkpoints manually
> ----------------------------------
>
> Key: FLINK-2976
> URL: https://issues.apache.org/jira/browse/FLINK-2976
> Project: Flink
> Issue Type: Improvement
> Components: Distributed Runtime
> Affects Versions: 0.10.0
> Reporter: Ufuk Celebi
> Fix For: 1.0.0
>
>
> Currently, all checkpointed state is bound to a job. After the job finishes
> all state is lost. In case of an HA cluster, jobs can live longer than the
> cluster, but they still suffer from the same issue when they finish.
> Multiple users have requested the feature to manually save a checkpoint in
> order to resume from it at a later point. This is especially important for
> production environments. As an example, consider upgrading your existing
> production Flink program. Currently, you loose all the state of your program.
> With the proposed mechanism, it will be possible to save a checkpoint, stop
> and update your program, and then continue your program with the checkpoint.
> The required operations can be simple:
> saveCheckpoint(JobID) => checkpointID: long
> loadCheckpoint(JobID, long) => void
> For the initial version, I would apply the following restriction:
> - The topology needs to stay the same (JobGraph parallelism, etc.)
> A user can configure this behaviour via the environment like the
> checkpointing interval. Furthermore, the user can trigger the save operation
> via the command line at arbitrary times and load a checkpoint when submitting
> a job, e.g.
> bin/flink checkpoint <JobID> => checkpointID: long
> and
> bin/flink run --loadCheckpoint JobID [latest saved checkpoint]
> bin/flink run --loadCheckpoint (JobID,long) [specific saved checkpoint]
> As far as I can tell, the required mechanisms are similar to the ones
> implemented for JobManager high availability. We need to make sure to persist
> the CompletedCheckpoint instances as a pointer to the checkpoint state and to
> *not* remove saved checkpoint state.
> On the client side, we need to give the job and its vertices the same IDs to
> allow mapping the checkpoint state.
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