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https://issues.apache.org/jira/browse/FLINK-10461?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16667360#comment-16667360
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ASF GitHub Bot commented on FLINK-10461:
----------------------------------------
azagrebin commented on a change in pull request #6777: [FLINK-10461] [State
Backends, Checkpointing] Speed up download files when restore from DFS
URL: https://github.com/apache/flink/pull/6777#discussion_r228970266
##########
File path:
flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDbStateDataTransfer.java
##########
@@ -0,0 +1,149 @@
+/*
+ * 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.contrib.streaming.state;
+
+import org.apache.flink.core.fs.CloseableRegistry;
+import org.apache.flink.core.fs.FSDataInputStream;
+import org.apache.flink.core.fs.FSDataOutputStream;
+import org.apache.flink.core.fs.FileSystem;
+import org.apache.flink.core.fs.Path;
+import org.apache.flink.runtime.concurrent.FutureUtils;
+import org.apache.flink.runtime.state.IncrementalKeyedStateHandle;
+import org.apache.flink.runtime.state.StateHandleID;
+import org.apache.flink.runtime.state.StreamStateHandle;
+
+import java.io.Closeable;
+import java.io.IOException;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+/**
+ * Data transfer utils for RocksDbKeyedStateBackend.
+ */
+public class RocksDbStateDataTransfer {
+
+ public static void transferAllStateDataToDirectory(
+ IncrementalKeyedStateHandle restoreStateHandle,
+ Path dest,
+ int resotreThreadNum,
+ CloseableRegistry closeableRegistry) throws Exception {
+
+ final Map<StateHandleID, StreamStateHandle> sstFiles =
+ restoreStateHandle.getSharedState();
+ final Map<StateHandleID, StreamStateHandle> miscFiles =
+ restoreStateHandle.getPrivateState();
+
+ transferAllDataFromStateHandles(sstFiles, dest,
resotreThreadNum, closeableRegistry);
+ transferAllDataFromStateHandles(miscFiles, dest,
resotreThreadNum, closeableRegistry);
+ }
+
+ /**
+ * Copies all the files from the given stream state handles to the
given path, renaming the files w.r.t. their
+ * {@link StateHandleID}.
+ */
+ private static void transferAllDataFromStateHandles(
+ Map<StateHandleID, StreamStateHandle> stateHandleMap,
+ Path restoreInstancePath,
+ int resotreThreadNum,
+ CloseableRegistry closeableRegistry
+ ) throws Exception {
+
+ final ExecutorService executorService =
Executors.newFixedThreadPool(resotreThreadNum);
+ List<CompletableFuture<Void>> futures = new LinkedList<>();
+ List<Closeable> closeables = new LinkedList<>();
+
+ try {
+ closeables.add(() -> executorService.shutdownNow());
Review comment:
I think the tasks should be first properly canceled and then
`executorService` should shutdown.
`executorService.shutdownNow` also calls `future.cancel` which is
interrupting the task thread.
At the moment `while (true)` in `copyStateDataHandleData` does not support
explicit cancelation.
I suggest to create an `running = AtomicBoolean(true)` in the beginning then
`while (true)` can be `while(running.get())`. This will allow to cancel all
tasks at once and shutdown `executorService` in one `closeable`:
`closeables.add(() -> { running.set(false); executorService.shutdownNow());
};`
List of `closeables` is not needed then.
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> Speed up download file procedure when restore
> ----------------------------------------------
>
> Key: FLINK-10461
> URL: https://issues.apache.org/jira/browse/FLINK-10461
> Project: Flink
> Issue Type: Improvement
> Components: State Backends, Checkpointing
> Reporter: Congxian Qiu
> Assignee: Congxian Qiu
> Priority: Major
> Labels: pull-request-available
>
> In the current master branch, the restore will download file from DFS, the
> download procedure are single-thread, this could speed up by using
> multi-thread for downloading states from DFS.
>
> In my company, the states will come to some terabytes, so the restore
> procedure will become a litter slow, after a bit digging, I find download
> states from DFS using single thread, this could using multi-thread for speed
> up.
> I test the time used for download states from DFS with ~2 terabytes states.
> With single thread it used 640+s, and 130+s when using 5 threads for download.
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