[FLINK-35025][Runtime/State] Introduce element order for async state …

…processing

flink-runtime/src/main/java/org/apache/flink/runtime/asyncprocessing/AsyncExecutionController.java

@@ -21,7 +21,9 @@
 import org.apache.flink.api.common.operators.MailboxExecutor;
 import org.apache.flink.api.common.state.v2.State;
 import org.apache.flink.core.state.InternalStateFuture;
+import org.apache.flink.util.FlinkRuntimeException;
 import org.apache.flink.util.Preconditions;
+import org.apache.flink.util.function.ThrowingRunnable;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -248,4 +250,23 @@ private void seizeCapacity() {
         setCurrentContext(storedContext);
         inFlightRecordNum.incrementAndGet();
     }
+
+    /**
+     * A helper to request a {@link StateRequestType#SYNC_POINT} and run a callback if it finishes
+     * (once the record is not blocked).
+     *
+     * @param callback the callback to run if it finishes (once the record is not blocked).
+     */
+    public void syncPointRequestWithCallback(ThrowingRunnable<Exception> callback) {
+        handleRequest(null, StateRequestType.SYNC_POINT, null)
+                .thenAccept(
+                        v -> {
+                            try {
+                                callback.run();
+                            } catch (Exception e) {
+                                // TODO: Properly handle the exception and fail the entire job.
+                                throw new FlinkRuntimeException("Unexpected runtime exception", e);
+                            }
+                        });
+    }
 }

flink-runtime/src/main/java/org/apache/flink/runtime/asyncprocessing/StateRequestBuffer.java

@@ -60,7 +60,11 @@ public StateRequestBuffer() {
     }
 
     void enqueueToActive(StateRequest<K, ?, ?> request) {
-        activeQueue.add(request);
+        if (request.getRequestType() == StateRequestType.SYNC_POINT) {
+            request.getFuture().complete(null);
+        } else {
+            activeQueue.add(request);
+        }
     }
 
     void enqueueToBlocking(StateRequest<K, ?, ?> request) {
@@ -83,7 +87,7 @@ RecordContext<K> tryActivateOneByKey(K key) {
         }
 
         StateRequest<K, ?, ?> stateRequest = blockingQueue.get(key).removeFirst();
-        activeQueue.add(stateRequest);
+        enqueueToActive(stateRequest);
         if (blockingQueue.get(key).isEmpty()) {
             blockingQueue.remove(key);
         }

flink-runtime/src/test/java/org/apache/flink/runtime/asyncprocessing/AsyncExecutionControllerTest.java

@@ -300,6 +300,50 @@ void testInFlightRecordControl() {
         }
     }
 
+    @Test
+    public void testSyncPoint() {
+        AtomicInteger counter = new AtomicInteger(0);
+
+        // Test the sync point processing without a key occupied.
+        RecordContext<String> recordContext = aec.buildContext("record", "key");
+        aec.setCurrentContext(recordContext);
+        recordContext.retain();
+        aec.syncPointRequestWithCallback(counter::incrementAndGet);
+        assertThat(counter.get()).isEqualTo(1);
+        assertThat(recordContext.getReferenceCount()).isEqualTo(1);
+        assertThat(aec.stateRequestsBuffer.activeQueueSize()).isEqualTo(0);
+        assertThat(aec.stateRequestsBuffer.blockingQueueSize()).isEqualTo(0);
+        assertThat(aec.keyAccountingUnit.occupiedCount()).isEqualTo(1);
+        recordContext.release();
+        assertThat(aec.keyAccountingUnit.occupiedCount()).isEqualTo(0);
+
+        counter.set(0);
+        // Test the sync point processing with a key occupied.
+        RecordContext<String> recordContext1 = aec.buildContext("record1", "occupied");
+        aec.setCurrentContext(recordContext1);
+        userCode.run();
+
+        RecordContext<String> recordContext2 = aec.buildContext("record2", "occupied");
+        aec.setCurrentContext(recordContext2);
+        aec.syncPointRequestWithCallback(counter::incrementAndGet);
+        recordContext2.retain();
+        assertThat(counter.get()).isEqualTo(0);
+        assertThat(recordContext2.getReferenceCount()).isGreaterThan(1);
+        assertThat(aec.stateRequestsBuffer.activeQueueSize()).isEqualTo(1);
+        assertThat(aec.stateRequestsBuffer.blockingQueueSize()).isEqualTo(1);
+        aec.triggerIfNeeded(true);
+        assertThat(counter.get()).isEqualTo(0);
+        assertThat(recordContext2.getReferenceCount()).isGreaterThan(1);
+        assertThat(aec.stateRequestsBuffer.activeQueueSize()).isEqualTo(1);
+        assertThat(aec.stateRequestsBuffer.blockingQueueSize()).isEqualTo(1);
+        aec.triggerIfNeeded(true);
+        assertThat(counter.get()).isEqualTo(1);
+        assertThat(recordContext2.getReferenceCount()).isEqualTo(1);
+        assertThat(aec.stateRequestsBuffer.activeQueueSize()).isEqualTo(0);
+        assertThat(aec.stateRequestsBuffer.blockingQueueSize()).isEqualTo(0);
+        recordContext2.release();
+    }
+
     private StateExecutor createStateExecutor() {
         TestAsyncStateBackend testAsyncStateBackend = new TestAsyncStateBackend();
         assertThat(testAsyncStateBackend.supportsAsyncKeyedStateBackend()).isTrue();

flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/operators/asyncprocessing/AbstractAsyncStateStreamOperator.java

@@ -32,6 +32,7 @@
 import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
 import org.apache.flink.streaming.runtime.tasks.StreamTask;
 import org.apache.flink.util.function.ThrowingConsumer;
+import org.apache.flink.util.function.ThrowingRunnable;
 
 /**
  * This operator is an abstract class that give the {@link AbstractStreamOperator} the ability to
@@ -65,6 +66,11 @@ public boolean isAsyncStateProcessingEnabled() {
         return true;
     }
 
+    @Override
+    public ElementOrder getElementOrder() {
+        return ElementOrder.RECORD_ORDER;
+    }
+
     @Override
     @SuppressWarnings("unchecked")
     public final <T> void setAsyncKeyedContextElement(
@@ -91,6 +97,12 @@ public final void postProcessElement() {
         currentProcessingContext.release();
     }
 
+    @Override
+    @SuppressWarnings("unchecked")
+    public final void preserveRecordOrderAndProcess(ThrowingRunnable<Exception> processing) {
+        asyncExecutionController.syncPointRequestWithCallback(processing);
+    }
+
     @Override
     @SuppressWarnings("unchecked")
     public final <T> ThrowingConsumer<StreamRecord<T>, Exception> getRecordProcessor(int inputId) {
@@ -99,26 +111,21 @@ public final <T> ThrowingConsumer<StreamRecord<T>, Exception> getRecordProcessor
         if (this instanceof TwoInputStreamOperator) {
             switch (inputId) {
                 case 1:
-                    return record -> {
-                        setAsyncKeyedContextElement(record, (KeySelector<T, ?>) stateKeySelector1);
-                        ((TwoInputStreamOperator) this).processElement1(record);
-                        postProcessElement();
-                    };
+                    return AsyncStateProcessing.<T>makeRecordProcessor(
+                            this,
+                            (KeySelector) stateKeySelector1,
+                            ((TwoInputStreamOperator) this)::processElement1);
                 case 2:
-                    return record -> {
-                        setAsyncKeyedContextElement(record, (KeySelector<T, ?>) stateKeySelector2);
-                        ((TwoInputStreamOperator) this).processElement2(record);
-                        postProcessElement();
-                    };
+                    return AsyncStateProcessing.<T>makeRecordProcessor(
+                            this,
+                            (KeySelector) stateKeySelector2,
+                            ((TwoInputStreamOperator) this)::processElement2);
                 default:
                     break;
             }
         } else if (this instanceof Input && inputId == 1) {
-            return record -> {
-                setAsyncKeyedContextElement(record, (KeySelector<T, ?>) stateKeySelector1);
-                ((Input) this).processElement(record);
-                postProcessElement();
-            };
+            return AsyncStateProcessing.<T>makeRecordProcessor(
+                    this, (KeySelector) stateKeySelector1, ((Input) this)::processElement);
         }
         throw new IllegalArgumentException(
                 String.format(
@@ -130,4 +137,9 @@ public final <T> ThrowingConsumer<StreamRecord<T>, Exception> getRecordProcessor
     AsyncExecutionController<?> getAsyncExecutionController() {
         return asyncExecutionController;
     }
+
+    @VisibleForTesting
+    RecordContext getCurrentProcessingContext() {
+        return currentProcessingContext;
+    }
 }

flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/operators/asyncprocessing/AbstractAsyncStateStreamOperatorV2.java

@@ -29,6 +29,7 @@
 import org.apache.flink.streaming.api.operators.StreamTaskStateInitializer;
 import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
 import org.apache.flink.util.function.ThrowingConsumer;
+import org.apache.flink.util.function.ThrowingRunnable;
 
 /**
  * This operator is an abstract class that give the {@link AbstractStreamOperatorV2} the ability to
@@ -67,6 +68,11 @@ public boolean isAsyncStateProcessingEnabled() {
         return true;
     }
 
+    @Override
+    public ElementOrder getElementOrder() {
+        return ElementOrder.RECORD_ORDER;
+    }
+
     @Override
     @SuppressWarnings("unchecked")
     public final <T> void setAsyncKeyedContextElement(
@@ -93,6 +99,12 @@ public final void postProcessElement() {
         currentProcessingContext.release();
     }
 
+    @Override
+    @SuppressWarnings("unchecked")
+    public final void preserveRecordOrderAndProcess(ThrowingRunnable<Exception> processing) {
+        asyncExecutionController.syncPointRequestWithCallback(processing);
+    }
+
     @Override
     public final <T> ThrowingConsumer<StreamRecord<T>, Exception> getRecordProcessor(int inputId) {
         // The real logic should be in First/SecondInputOfTwoInput#getRecordProcessor.
@@ -105,4 +117,9 @@ public final <T> ThrowingConsumer<StreamRecord<T>, Exception> getRecordProcessor
     AsyncExecutionController<?> getAsyncExecutionController() {
         return asyncExecutionController;
     }
+
+    @VisibleForTesting
+    RecordContext getCurrentProcessingContext() {
+        return currentProcessingContext;
+    }
 }

flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/operators/asyncprocessing/AsyncStateProcessing.java

@@ -56,10 +56,23 @@ static <T> ThrowingConsumer<StreamRecord<T>, Exception> makeRecordProcessor(
             AsyncStateProcessingOperator asyncOperator,
             KeySelector<T, ?> keySelector,
             ThrowingConsumer<StreamRecord<T>, Exception> processor) {
-        return (record) -> {
-            asyncOperator.setAsyncKeyedContextElement(record, keySelector);
-            processor.accept(record);
-            asyncOperator.postProcessElement();
-        };
+        switch (asyncOperator.getElementOrder()) {
+            case RECORD_ORDER:
+                return (record) -> {
+                    asyncOperator.setAsyncKeyedContextElement(record, keySelector);
+                    asyncOperator.preserveRecordOrderAndProcess(() -> processor.accept(record));
+                    asyncOperator.postProcessElement();
+                };
+            case FIRST_STATE_ORDER:
+                return (record) -> {
+                    asyncOperator.setAsyncKeyedContextElement(record, keySelector);
+                    processor.accept(record);
+                    asyncOperator.postProcessElement();
+                };
+            default:
+                throw new UnsupportedOperationException(
+                        "Unknown element order for async processing:"
+                                + asyncOperator.getElementOrder());
+        }
     }
 }

flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/operators/asyncprocessing/AsyncStateProcessingOperator.java

@@ -21,6 +21,7 @@
 import org.apache.flink.annotation.Internal;
 import org.apache.flink.api.java.functions.KeySelector;
 import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
+import org.apache.flink.util.function.ThrowingRunnable;
 
 /**
  * A more detailed interface based on {@link AsyncStateProcessing}, which gives the essential
@@ -29,6 +30,9 @@
 @Internal
 public interface AsyncStateProcessingOperator extends AsyncStateProcessing {
 
+    /** Get the {@link ElementOrder} of this operator. */
+    ElementOrder getElementOrder();
+
     /**
      * Set key context for async state processing.
      *
@@ -41,4 +45,12 @@ <T> void setAsyncKeyedContextElement(StreamRecord<T> record, KeySelector<T, ?> k
 
     /** A callback that will be triggered after an element finishes {@code processElement}. */
     void postProcessElement();
+
+    /**
+     * Check the order of same-key record, and then process the record. Mainly used when the {@link
+     * #getElementOrder()} returns {@link ElementOrder#RECORD_ORDER}.
+     *
+     * @param processing the record processing logic.
+     */
+    void preserveRecordOrderAndProcess(ThrowingRunnable<Exception> processing);
 }

flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/operators/asyncprocessing/ElementOrder.java

@@ -0,0 +1,42 @@
+/*
+ * 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.streaming.runtime.operators.asyncprocessing;
+
+import org.apache.flink.annotation.Internal;
+
+/**
+ * This enum defines the element order of being processed. Only the elements with the same key
+ * should be considered here. We should keep this internal and away from API module for now, until
+ * we could see the concrete need for {@link #FIRST_STATE_ORDER} from average users.
+ */
+@Internal
+public enum ElementOrder {
+    /**
+     * Treat the record processing as a whole, meaning that any {@code processElement} call for the
+     * elements with same key should follow the order of record arrival AND no parallel run is
+     * allowed.
+     */
+    RECORD_ORDER,
+
+    /**
+     * The {@code processElement} call will be invoked on record arrival, but may be blocked at the
+     * first state accessing if there is a preceding same-key record under processing.
+     */
+    FIRST_STATE_ORDER,
+}