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https://issues.apache.org/jira/browse/FLINK-10461?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16667359#comment-16667359
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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_r228970609
##########
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());
+
closeableRegistry.registerCloseable(((LinkedList<Closeable>)
closeables).getLast());
+
+ for (Map.Entry<StateHandleID, StreamStateHandle> entry
: stateHandleMap.entrySet()) {
+ StateHandleID stateHandleID = entry.getKey();
+ StreamStateHandle remoteFileHandle =
entry.getValue();
+
+ if (resotreThreadNum > 1) {
+ CompletableFuture<Void> future =
CompletableFuture.runAsync(() -> {
+ try {
+
copyStateDataHandleData(new Path(restoreInstancePath,
stateHandleID.toString()), remoteFileHandle, closeableRegistry);
+ } catch (IOException e) {
Review comment:
the exception handling can go inside `copyStateDataHandleData`.
`new Path(restoreInstancePath, stateHandleID.toString())` can be a variable
to reduce the line length.
I would create a list of `Runnable`'s:
```
Path path = new Path(restoreInstancePath, stateHandleID.toString());
runnables.add( -> copyStateDataHandleData(path, remoteFileHandle,
closeableRegistry));
```
and then have separate code for `resotreThreadNum > 1` and `resotreThreadNum
== 1`.
`executorService` currently is not used for `resotreThreadNum == 1` but
created.
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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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