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Posted to issues@flink.apache.org by "JunRuiLee (via GitHub)" <gi...@apache.org> on 2024/02/29 11:53:03 UTC
[PR] [FLINK-33984][runtime] Support batch snapshot for OperatorCoordinator. [flink]
JunRuiLee opened a new pull request, #24415:
URL: https://github.com/apache/flink/pull/24415
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## What is the purpose of the change
Support batch snapshot for OperatorCoordinator.
## Brief change log
Support batch snapshot for OperatorCoordinator.
## Verifying this change
This change added tests and can be verified by SourceCoordinatorTest#testBatchSnapshotCoordinatorAndRestore and SplitAssignmentTrackerTest#testSnapshotStateAndRestoreState
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): (yes / **no**)
- The public API, i.e., is any changed class annotated with `@Public(Evolving)`: (**yes** / no)
- The serializers: (yes / **no** / don't know)
- The runtime per-record code paths (performance sensitive): (yes / **no** / don't know)
- Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (yes / **no** / don't know)
- The S3 file system connector: (yes / **no** / don't know)
## Documentation
- Does this pull request introduce a new feature? (**yes** / no)
- If yes, how is the feature documented? (not applicable / docs / JavaDocs / **not documented**)
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Re: [PR] [FLINK-33984][runtime] Support batch snapshot for OperatorCoordinator. [flink]
Posted by "flinkbot (via GitHub)" <gi...@apache.org>.
flinkbot commented on PR #24415:
URL: https://github.com/apache/flink/pull/24415#issuecomment-1970983347
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## CI report:
* 4c870a5a541f7151f18e8b869d1a7e5e2bef961b UNKNOWN
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Re: [PR] [FLINK-33984][runtime] Support batch snapshot for OperatorCoordinator. [flink]
Posted by "zhuzhurk (via GitHub)" <gi...@apache.org>.
zhuzhurk commented on code in PR #24415:
URL: https://github.com/apache/flink/pull/24415#discussion_r1538868578
##########
flink-core/src/main/java/org/apache/flink/api/connector/source/SupportsBatchSnapshot.java:
##########
@@ -0,0 +1,30 @@
+/*
+ * 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.api.connector.source;
+
+import org.apache.flink.annotation.PublicEvolving;
+
+/**
+ * An identifier interface for {@link SplitEnumerator}, which is used to support taking snapshot in
+ * no-checkpoint/batch scenarios (for example to support job recovery in batch jobs). Once a {@link
+ * SplitEnumerator} implements this interface, its {@link SplitEnumerator#snapshotState} method
+ * needs to accept -1 (NO_CHECKPOINT) as the argument.
+ */
+@PublicEvolving
+public interface SupportsBatchSnapshot {}
Review Comment:
-> A decorative interface {@link SplitEnumerator}. Implementing it means the split enumerator {@link SplitEnumerator#snapshotState} method supports taking snapshot in batch processing scenarios. In such scenarios, the checkpointId will always be -1.
I think `-1` does not mean `no-checkpoint` in this case.
##########
flink-runtime/src/main/java/org/apache/flink/runtime/operators/coordination/OperatorCoordinatorHolder.java:
##########
@@ -437,9 +437,8 @@ private void setupSubtaskGateway(final SubtaskAccess sta) {
final SubtaskGatewayImpl gateway =
new SubtaskGatewayImpl(sta, mainThreadExecutor, unconfirmedEvents);
- // When concurrent execution attempts is supported, the checkpoint must have been disabled.
- // Thus, we don't need to maintain subtaskGatewayMap
- if (!context.isConcurrentExecutionAttemptsSupported()) {
+ // We don't need to maintain subtaskGatewayMap when checkpoint coordinator is null.
+ if (context.getCheckpointCoordinator() != null) {
subtaskGatewayMap.put(gateway.getSubtask(), gateway);
Review Comment:
The comments of the field `subtaskGatewayMap` is not updated.
##########
flink-runtime/src/main/java/org/apache/flink/runtime/operators/coordination/RecreateOnResetOperatorCoordinator.java:
##########
@@ -160,6 +160,17 @@ public void resetToCheckpoint(final long checkpointId, @Nullable final byte[] ch
});
}
+ @Override
+ public boolean supportsBatchSnapshot() {
+ try {
+ return getInternalCoordinator().supportsBatchSnapshot();
+ } catch (Exception e) {
+ String msg = "Could not get internal coordinator";
+ LOG.error(msg, e);
+ throw new RuntimeException(msg, e);
+ }
Review Comment:
`getInternalCoordinator()` can be heavy and block the main thread.
Given that this method should not trigger any actions on the coordinator, maybe we can directly check `coordinator.internalCoordinator` that it is not null and invoke `internalCoordinator.supportsBatchSnapshot()`.
##########
flink-runtime/src/main/java/org/apache/flink/runtime/source/coordinator/SourceCoordinatorSerdeUtils.java:
##########
@@ -53,4 +62,62 @@ static byte[] readBytes(DataInputStream in, int size) throws IOException {
in.readFully(bytes);
return bytes;
}
+
+ /** Serialize the assignment by checkpoint ids. */
+ static <SplitT> byte[] writeAssignments(
+ Map<Integer, LinkedHashSet<SplitT>> assignments,
+ SimpleVersionedSerializer<SplitT> splitSerializer)
+ throws IOException {
+ try (ByteArrayOutputStream baos = new ByteArrayOutputStream();
+ DataOutputStream out = new DataOutputViewStreamWrapper(baos)) {
+ // SplitSerializer version.
Review Comment:
useless comment
##########
flink-runtime/src/main/java/org/apache/flink/runtime/source/coordinator/SplitAssignmentTracker.java:
##########
@@ -65,6 +69,33 @@ public void onCheckpoint(long checkpointId) throws Exception {
uncheckpointedAssignments = new HashMap<>();
}
+ /**
+ * Take a snapshot of the split assignments.
+ *
+ * @param checkpointId the id of the ongoing checkpoint
+ */
+ public byte[] snapshotState(
+ long checkpointId, SimpleVersionedSerializer<SplitT> splitSerializer) throws Exception {
+ checkState(checkpointId == NO_CHECKPOINT);
+ return SourceCoordinatorSerdeUtils.writeAssignments(
+ uncheckpointedAssignments, splitSerializer);
+ }
+
+ /**
+ * Restore the state of the SplitAssignmentTracker.
+ *
+ * @param splitSerializer The serializer of the splits.
+ * @param assignmentData The state of the SplitAssignmentTracker.
+ * @throws Exception when the state deserialization fails.
+ */
+ public void restoreState(
+ SimpleVersionedSerializer<SplitT> splitSerializer, byte[] assignmentData)
+ throws Exception {
+ // Read the split assignments by checkpoint id.
Review Comment:
The comment is outdated.
##########
flink-runtime/src/main/java/org/apache/flink/runtime/source/coordinator/SourceCoordinatorSerdeUtils.java:
##########
@@ -53,4 +62,62 @@ static byte[] readBytes(DataInputStream in, int size) throws IOException {
in.readFully(bytes);
return bytes;
}
+
+ /** Serialize the assignment by checkpoint ids. */
Review Comment:
The comment is outdated.
##########
flink-runtime/src/main/java/org/apache/flink/runtime/operators/coordination/OperatorCoordinator.java:
##########
@@ -234,6 +234,16 @@ default void notifyCheckpointAborted(long checkpointId) {}
*/
void executionAttemptReady(int subtask, int attemptNumber, SubtaskGateway gateway);
+ /**
+ * Whether the operator coordinator supports taking snapshot in no-checkpoint/batch scenarios.
+ * If it returns true, it's {@link OperatorCoordinator#checkpointCoordinator} and {@link
+ * OperatorCoordinator#resetToCheckpoint} methods need to accept {@link
+ * OperatorCoordinator#NO_CHECKPOINT} as the value of checkpoint id. Otherwise, returns false.
+ */
+ default boolean supportsBatchSnapshot() {
Review Comment:
-> Whether the operator coordinator supports taking snapshot in no-checkpoint/batch scenarios. If it returns true, the {@link OperatorCoordinator#checkpointCoordinator} and {@link OperatorCoordinator#resetToCheckpoint} methods supports taking snapshot and restoring from a snapshot in batch processing scenarios. In such scenarios, the checkpointId will always be -1.
##########
flink-runtime/src/main/java/org/apache/flink/runtime/operators/coordination/OperatorCoordinatorHolder.java:
##########
@@ -314,7 +314,8 @@ private void checkpointCoordinatorInternal(
(success, failure) -> {
if (failure != null) {
result.completeExceptionally(failure);
- } else if (closeGateways(checkpointId)) {
+ } else if (checkpointId == OperatorCoordinator.NO_CHECKPOINT
Review Comment:
It's a bit weird to say `NO_CHECKPOINT` and the description of it is not right in batch scenarios. I prefer to introduce a new const `OperatorCoordinator.BATCH_CHECKPOINT_ID` which is also -1.
##########
flink-runtime/src/test/java/org/apache/flink/runtime/operators/coordination/OperatorCoordinatorHolderTest.java:
##########
@@ -574,8 +574,7 @@ public boolean hasFinishedTasks() {
},
IteratorChain::new,
false),
- new CheckpointStatsTracker(
- 1, new WatermarkStrategyTest.DummyMetricGroup(), jobId)));
+ new CheckpointStatsTracker(1, new UnregisteredMetricsGroup(), jobId)));
Review Comment:
This change looks good to me. Just wondering what would happen without this change?
##########
flink-runtime/src/main/java/org/apache/flink/runtime/operators/coordination/SubtaskGatewayImpl.java:
##########
@@ -185,11 +185,6 @@ void markForCheckpoint(long checkpointId) {
if (checkpointId > latestAttemptedCheckpointId) {
currentMarkedCheckpointIds.add(checkpointId);
latestAttemptedCheckpointId = checkpointId;
- } else {
Review Comment:
Maybe `else if (checkpointId != BATCH_CHECKPOINT_ID)`
##########
flink-runtime/src/main/java/org/apache/flink/runtime/source/coordinator/SourceCoordinatorSerdeUtils.java:
##########
@@ -53,4 +62,62 @@ static byte[] readBytes(DataInputStream in, int size) throws IOException {
in.readFully(bytes);
return bytes;
}
+
+ /** Serialize the assignment by checkpoint ids. */
+ static <SplitT> byte[] writeAssignments(
Review Comment:
I prefer to name the two methods as `serializeAssignments` and `deserializeAssignments`.
##########
flink-runtime/src/main/java/org/apache/flink/runtime/source/coordinator/SplitAssignmentTracker.java:
##########
@@ -65,6 +69,33 @@ public void onCheckpoint(long checkpointId) throws Exception {
uncheckpointedAssignments = new HashMap<>();
}
+ /**
+ * Take a snapshot of the split assignments.
+ *
+ * @param checkpointId the id of the ongoing checkpoint
+ */
+ public byte[] snapshotState(
+ long checkpointId, SimpleVersionedSerializer<SplitT> splitSerializer) throws Exception {
+ checkState(checkpointId == NO_CHECKPOINT);
Review Comment:
Looks to me the `checkpointId` param is not needed.
##########
flink-runtime/src/test/java/org/apache/flink/runtime/source/coordinator/SplitAssignmentTrackerTest.java:
##########
@@ -108,15 +105,15 @@ public void testOnCheckpointComplete() throws Exception {
// Complete the first checkpoint.
tracker.onCheckpointComplete(checkpointId1);
- assertNull(tracker.assignmentsByCheckpointId(checkpointId1));
+ assertThat(tracker.assignmentsByCheckpointId(checkpointId1)).isNull();
verifyAssignment(
Arrays.asList("3"), tracker.assignmentsByCheckpointId(checkpointId2).get(0));
verifyAssignment(
Arrays.asList("4", "5"), tracker.assignmentsByCheckpointId(checkpointId2).get(1));
}
@Test
- public void testGetAndRemoveUncheckpointedAssignment() throws Exception {
+ void testGetAndRemoveUncheckpointedAssignment() throws Exception {
Review Comment:
There is one more test case below which is not fixed.
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Re: [PR] [FLINK-33984][runtime] Support batch snapshot for OperatorCoordinator. [flink]
Posted by "JunRuiLee (via GitHub)" <gi...@apache.org>.
JunRuiLee commented on PR #24415:
URL: https://github.com/apache/flink/pull/24415#issuecomment-2024510405
@zhuzhurk Thanks for your reviews, I've updated this pr accordingly, PTAL.
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Re: [PR] [FLINK-33984][runtime] Support batch snapshot for OperatorCoordinator. [flink]
Posted by "zhuzhurk (via GitHub)" <gi...@apache.org>.
zhuzhurk closed pull request #24415: [FLINK-33984][runtime] Support batch snapshot for OperatorCoordinator.
URL: https://github.com/apache/flink/pull/24415
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Re: [PR] [FLINK-33984][runtime] Support batch snapshot for OperatorCoordinator. [flink]
Posted by "JunRuiLee (via GitHub)" <gi...@apache.org>.
JunRuiLee commented on code in PR #24415:
URL: https://github.com/apache/flink/pull/24415#discussion_r1542392137
##########
flink-runtime/src/test/java/org/apache/flink/runtime/operators/coordination/OperatorCoordinatorHolderTest.java:
##########
@@ -574,8 +574,7 @@ public boolean hasFinishedTasks() {
},
IteratorChain::new,
false),
- new CheckpointStatsTracker(
- 1, new WatermarkStrategyTest.DummyMetricGroup(), jobId)));
+ new CheckpointStatsTracker(1, new UnregisteredMetricsGroup(), jobId)));
Review Comment:
This change was mistakenly included in the wrong commit; it should be part of commit 54ccfc4f. I will update it before merging.
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