StephanEwen commented on a change in pull request #14181:
URL: https://github.com/apache/flink/pull/14181#discussion_r528936334
##########
File path:
flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/tasks/SourceOperatorStreamTask.java
##########
@@ -43,9 +51,11 @@
@Internal
public class SourceOperatorStreamTask<T> extends StreamTask<T,
SourceOperator<T, ?>> {
private AsyncDataOutputToOutput<T> output;
+ private boolean isExternallyInducedSource;
public SourceOperatorStreamTask(Environment env) throws Exception {
super(env);
+ this.isExternallyInducedSource = false;
Review comment:
nit: this is not necessary, false is the default.
##########
File path:
flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/tasks/SourceOperatorStreamTask.java
##########
@@ -66,6 +76,43 @@ public void init() {
operatorChain);
}
+ @Override
+ protected void beforeInvoke() throws Exception {
Review comment:
We are creating `input` and the `inputProcessor` twice now, once in
`init()` and once on `beforeInvoke()`. Can we add this code here to init to
avoid creating this twice? I think creating it twice may have some unexpected
side effects in certain cases.
##########
File path:
flink-core/src/main/java/org/apache/flink/api/connector/source/ExternallyInducedSourceReader.java
##########
@@ -0,0 +1,57 @@
+/*
+ * 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;
+
+import java.util.Optional;
+
+/**
+ * Sources that implement this interface do not trigger checkpoints when
receiving a
+ * trigger message from the checkpoint coordinator, but when their input
data/events
+ * indicate that a checkpoint should be triggered.
+ *
+ * <p>The ExternallyInducedSourceReader tells the Flink runtime that a
checkpoint needs to
+ * be made by returning a checkpointId when shouldTriggerCheckpoint() is
invoked.
+ *
+ * <p>The implementations typically works together with the SplitEnumerator
which informs
+ * the external system to trigger a checkpoint.
+ *
+ * @param <T> The type of records produced by the source.
+ * @param <SplitT> The type of splits handled by the source.
+ */
+@PublicEvolving
+public interface ExternallyInducedSourceReader<T, SplitT extends SourceSplit>
+ extends SourceReader<T, SplitT> {
+
+ /**
+ * A method that informs the Flink runtime whether a checkpoint should
be triggered on
+ * this Source.
+ *
+ * <p>This method is invoked when the previous {@link
#pollNext(ReaderOutput)}
+ * returns {@link
org.apache.flink.core.io.InputStatus#NOTHING_AVAILABLE}, to check
+ * if the source needs to be checkpointed.
+ *
+ * <p>If a CheckpointId is returned, a checkpoint will be triggered on
this source reader.
+ * Otherwise, Flink runtime will continue to process the records.
+ *
+ * @return An optional checkpoint ID that Flink runtime should take a
checkpoint for.
+ */
+ Optional<Long> shouldTriggerCheckpoint();
Review comment:
If we want to switch from polling to notifying, we could change this
method to
```java
void registerCheckpointTrigger(Consumer<Long> trigger);
```
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