masteryhx commented on a change in pull request #18224:
URL: https://github.com/apache/flink/pull/18224#discussion_r807107658



##########
File path: 
flink-tests/src/test/java/org/apache/flink/test/checkpointing/ChangelogPeriodicMaterializationITCase.java
##########
@@ -0,0 +1,190 @@
+/*
+ * 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.test.checkpointing;
+
+import org.apache.flink.api.common.restartstrategy.RestartStrategies;
+import org.apache.flink.configuration.Configuration;
+import org.apache.flink.configuration.StateChangelogOptions;
+import org.apache.flink.runtime.state.AbstractStateBackend;
+import org.apache.flink.runtime.state.KeyedStateHandle;
+import org.apache.flink.runtime.state.SnapshotResult;
+import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
+import org.apache.flink.util.function.FutureTaskWithException;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.time.Duration;
+import java.util.concurrent.Future;
+import java.util.concurrent.RunnableFuture;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * This verifies that checkpointing works correctly for Changelog state 
backend with materialized
+ * state / non-materialized state.
+ */
+public class ChangelogPeriodicMaterializationITCase
+        extends ChangelogPeriodicMaterializationTestBase {
+
+    private static final AtomicBoolean triggerDelegatedSnapshot = new 
AtomicBoolean();
+
+    public ChangelogPeriodicMaterializationITCase(AbstractStateBackend 
delegatedStateBackend) {
+        super(delegatedStateBackend);
+    }
+
+    @Before
+    public void setup() throws Exception {
+        super.setup();
+        triggerDelegatedSnapshot.set(false);
+    }
+
+    /** Recovery from checkpoint only containing non-materialized state. */
+    @Test
+    public void testNonMaterialization() throws Exception {
+        StreamExecutionEnvironment env = 
StreamExecutionEnvironment.getExecutionEnvironment();
+        env.enableCheckpointing(10)
+                .enableChangelogStateBackend(true)
+                .getCheckpointConfig()
+                .setCheckpointStorage(TEMPORARY_FOLDER.newFolder().toURI());
+        env.setStateBackend(new 
DelegatedStateBackendWrapper(delegatedStateBackend, t -> t))
+                .setRestartStrategy(RestartStrategies.fixedDelayRestart(1, 0));
+        env.configure(
+                new Configuration()
+                        .set(
+                                
StateChangelogOptions.PERIODIC_MATERIALIZATION_INTERVAL,
+                                Duration.ofMinutes(3)));
+        waitAndAssert(
+                env,
+                buildStreamGraph(
+                        env,
+                        new ControlledSource() {
+                            @Override
+                            protected void beforeElement() throws Exception {
+                                if (getRuntimeContext().getAttemptNumber() == 0
+                                        && currentIndex == TOTAL_ELEMENTS / 2) 
{
+                                    waitWhile(() -> 
completedCheckpointNum.get() <= 0);
+                                    throwArtificialFailure();
+                                }
+                            }
+                        }));
+    }
+
+    /** Recovery from checkpoint containing non-materialized state and 
materialized state. */
+    @Test
+    public void testMaterialization() throws Exception {
+        StreamExecutionEnvironment env = 
StreamExecutionEnvironment.getExecutionEnvironment();
+        env.enableCheckpointing(10)
+                .enableChangelogStateBackend(true)
+                .getCheckpointConfig()
+                .setCheckpointStorage(TEMPORARY_FOLDER.newFolder().toURI());
+
+        
SerializableFunctionWithException<RunnableFuture<SnapshotResult<KeyedStateHandle>>>
+                snapshotResultConsumer =
+                        snapshotResultFuture -> {
+                            PENDING_MATERIALIZATION.add(snapshotResultFuture);
+                            return snapshotResultFuture;
+                        };
+        env.setStateBackend(
+                        new DelegatedStateBackendWrapper(
+                                delegatedStateBackend, snapshotResultConsumer))
+                .setRestartStrategy(RestartStrategies.fixedDelayRestart(2, 0));
+        env.configure(
+                new Configuration()
+                        .set(
+                                
StateChangelogOptions.PERIODIC_MATERIALIZATION_INTERVAL,
+                                Duration.ofMillis(10)));
+        waitAndAssert(
+                env,
+                buildStreamGraph(
+                        env,
+                        new ControlledSource() {
+                            @Override
+                            protected void beforeElement() throws Exception {
+                                if (getRuntimeContext().getAttemptNumber() == 0
+                                        && currentIndex == TOTAL_ELEMENTS / 4) 
{
+                                    waitWhile(
+                                            () ->
+                                                    
completedCheckpointNum.get() <= 0
+                                                            || 
PENDING_MATERIALIZATION.stream()
+                                                                    
.noneMatch(Future::isDone));
+                                    PENDING_MATERIALIZATION.clear();
+                                    throwArtificialFailure();

Review comment:
       Yes, you are right. I plan to add a condition to check the checkpoint 
status (like `ResumeCheckpointManuallyITCase#findExternalizedCheckpoint`), and 
the wrappered state backend will still be used  because I cannot find other way 
to make materialization fail(for `testFailedMaterialization`).
   WDYT?

##########
File path: 
flink-tests/src/test/java/org/apache/flink/test/checkpointing/ChangelogPeriodicMaterializationITCase.java
##########
@@ -0,0 +1,190 @@
+/*
+ * 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.test.checkpointing;
+
+import org.apache.flink.api.common.restartstrategy.RestartStrategies;
+import org.apache.flink.configuration.Configuration;
+import org.apache.flink.configuration.StateChangelogOptions;
+import org.apache.flink.runtime.state.AbstractStateBackend;
+import org.apache.flink.runtime.state.KeyedStateHandle;
+import org.apache.flink.runtime.state.SnapshotResult;
+import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
+import org.apache.flink.util.function.FutureTaskWithException;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.time.Duration;
+import java.util.concurrent.Future;
+import java.util.concurrent.RunnableFuture;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * This verifies that checkpointing works correctly for Changelog state 
backend with materialized
+ * state / non-materialized state.
+ */
+public class ChangelogPeriodicMaterializationITCase
+        extends ChangelogPeriodicMaterializationTestBase {
+
+    private static final AtomicBoolean triggerDelegatedSnapshot = new 
AtomicBoolean();
+
+    public ChangelogPeriodicMaterializationITCase(AbstractStateBackend 
delegatedStateBackend) {
+        super(delegatedStateBackend);
+    }
+
+    @Before
+    public void setup() throws Exception {
+        super.setup();
+        triggerDelegatedSnapshot.set(false);
+    }
+
+    /** Recovery from checkpoint only containing non-materialized state. */
+    @Test
+    public void testNonMaterialization() throws Exception {
+        StreamExecutionEnvironment env = 
StreamExecutionEnvironment.getExecutionEnvironment();
+        env.enableCheckpointing(10)
+                .enableChangelogStateBackend(true)
+                .getCheckpointConfig()
+                .setCheckpointStorage(TEMPORARY_FOLDER.newFolder().toURI());
+        env.setStateBackend(new 
DelegatedStateBackendWrapper(delegatedStateBackend, t -> t))
+                .setRestartStrategy(RestartStrategies.fixedDelayRestart(1, 0));
+        env.configure(
+                new Configuration()
+                        .set(
+                                
StateChangelogOptions.PERIODIC_MATERIALIZATION_INTERVAL,
+                                Duration.ofMinutes(3)));
+        waitAndAssert(
+                env,
+                buildStreamGraph(
+                        env,
+                        new ControlledSource() {
+                            @Override
+                            protected void beforeElement() throws Exception {
+                                if (getRuntimeContext().getAttemptNumber() == 0
+                                        && currentIndex == TOTAL_ELEMENTS / 2) 
{
+                                    waitWhile(() -> 
completedCheckpointNum.get() <= 0);
+                                    throwArtificialFailure();
+                                }
+                            }
+                        }));
+    }
+
+    /** Recovery from checkpoint containing non-materialized state and 
materialized state. */
+    @Test
+    public void testMaterialization() throws Exception {
+        StreamExecutionEnvironment env = 
StreamExecutionEnvironment.getExecutionEnvironment();
+        env.enableCheckpointing(10)
+                .enableChangelogStateBackend(true)
+                .getCheckpointConfig()
+                .setCheckpointStorage(TEMPORARY_FOLDER.newFolder().toURI());
+
+        
SerializableFunctionWithException<RunnableFuture<SnapshotResult<KeyedStateHandle>>>
+                snapshotResultConsumer =
+                        snapshotResultFuture -> {
+                            PENDING_MATERIALIZATION.add(snapshotResultFuture);
+                            return snapshotResultFuture;
+                        };
+        env.setStateBackend(
+                        new DelegatedStateBackendWrapper(
+                                delegatedStateBackend, snapshotResultConsumer))
+                .setRestartStrategy(RestartStrategies.fixedDelayRestart(2, 0));
+        env.configure(
+                new Configuration()
+                        .set(
+                                
StateChangelogOptions.PERIODIC_MATERIALIZATION_INTERVAL,
+                                Duration.ofMillis(10)));
+        waitAndAssert(
+                env,
+                buildStreamGraph(
+                        env,
+                        new ControlledSource() {
+                            @Override
+                            protected void beforeElement() throws Exception {
+                                if (getRuntimeContext().getAttemptNumber() == 0
+                                        && currentIndex == TOTAL_ELEMENTS / 4) 
{
+                                    waitWhile(
+                                            () ->
+                                                    
completedCheckpointNum.get() <= 0
+                                                            || 
PENDING_MATERIALIZATION.stream()
+                                                                    
.noneMatch(Future::isDone));
+                                    PENDING_MATERIALIZATION.clear();
+                                    throwArtificialFailure();
+                                } else if 
(getRuntimeContext().getAttemptNumber() == 1
+                                        && currentIndex == TOTAL_ELEMENTS / 2) 
{

Review comment:
       I just want to fail it twice:
   consume some elements -> fail -> recovery -> continue to consume some 
elements -> fail -> recovery

##########
File path: 
flink-tests/src/test/java/org/apache/flink/test/checkpointing/ChangelogPeriodicMaterializationITCase.java
##########
@@ -0,0 +1,190 @@
+/*
+ * 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.test.checkpointing;
+
+import org.apache.flink.api.common.restartstrategy.RestartStrategies;
+import org.apache.flink.configuration.Configuration;
+import org.apache.flink.configuration.StateChangelogOptions;
+import org.apache.flink.runtime.state.AbstractStateBackend;
+import org.apache.flink.runtime.state.KeyedStateHandle;
+import org.apache.flink.runtime.state.SnapshotResult;
+import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
+import org.apache.flink.util.function.FutureTaskWithException;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.time.Duration;
+import java.util.concurrent.Future;
+import java.util.concurrent.RunnableFuture;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * This verifies that checkpointing works correctly for Changelog state 
backend with materialized
+ * state / non-materialized state.
+ */
+public class ChangelogPeriodicMaterializationITCase
+        extends ChangelogPeriodicMaterializationTestBase {
+
+    private static final AtomicBoolean triggerDelegatedSnapshot = new 
AtomicBoolean();
+
+    public ChangelogPeriodicMaterializationITCase(AbstractStateBackend 
delegatedStateBackend) {
+        super(delegatedStateBackend);
+    }
+
+    @Before
+    public void setup() throws Exception {
+        super.setup();
+        triggerDelegatedSnapshot.set(false);
+    }
+
+    /** Recovery from checkpoint only containing non-materialized state. */
+    @Test
+    public void testNonMaterialization() throws Exception {
+        StreamExecutionEnvironment env = 
StreamExecutionEnvironment.getExecutionEnvironment();
+        env.enableCheckpointing(10)
+                .enableChangelogStateBackend(true)
+                .getCheckpointConfig()
+                .setCheckpointStorage(TEMPORARY_FOLDER.newFolder().toURI());
+        env.setStateBackend(new 
DelegatedStateBackendWrapper(delegatedStateBackend, t -> t))
+                .setRestartStrategy(RestartStrategies.fixedDelayRestart(1, 0));
+        env.configure(
+                new Configuration()
+                        .set(
+                                
StateChangelogOptions.PERIODIC_MATERIALIZATION_INTERVAL,
+                                Duration.ofMinutes(3)));
+        waitAndAssert(
+                env,
+                buildStreamGraph(
+                        env,
+                        new ControlledSource() {
+                            @Override
+                            protected void beforeElement() throws Exception {
+                                if (getRuntimeContext().getAttemptNumber() == 0
+                                        && currentIndex == TOTAL_ELEMENTS / 2) 
{
+                                    waitWhile(() -> 
completedCheckpointNum.get() <= 0);
+                                    throwArtificialFailure();
+                                }
+                            }
+                        }));
+    }
+
+    /** Recovery from checkpoint containing non-materialized state and 
materialized state. */
+    @Test
+    public void testMaterialization() throws Exception {
+        StreamExecutionEnvironment env = 
StreamExecutionEnvironment.getExecutionEnvironment();
+        env.enableCheckpointing(10)
+                .enableChangelogStateBackend(true)
+                .getCheckpointConfig()
+                .setCheckpointStorage(TEMPORARY_FOLDER.newFolder().toURI());
+
+        
SerializableFunctionWithException<RunnableFuture<SnapshotResult<KeyedStateHandle>>>
+                snapshotResultConsumer =
+                        snapshotResultFuture -> {
+                            PENDING_MATERIALIZATION.add(snapshotResultFuture);
+                            return snapshotResultFuture;
+                        };
+        env.setStateBackend(
+                        new DelegatedStateBackendWrapper(
+                                delegatedStateBackend, snapshotResultConsumer))
+                .setRestartStrategy(RestartStrategies.fixedDelayRestart(2, 0));
+        env.configure(
+                new Configuration()
+                        .set(
+                                
StateChangelogOptions.PERIODIC_MATERIALIZATION_INTERVAL,
+                                Duration.ofMillis(10)));
+        waitAndAssert(
+                env,
+                buildStreamGraph(
+                        env,
+                        new ControlledSource() {
+                            @Override
+                            protected void beforeElement() throws Exception {
+                                if (getRuntimeContext().getAttemptNumber() == 0
+                                        && currentIndex == TOTAL_ELEMENTS / 4) 
{
+                                    waitWhile(
+                                            () ->
+                                                    
completedCheckpointNum.get() <= 0
+                                                            || 
PENDING_MATERIALIZATION.stream()
+                                                                    
.noneMatch(Future::isDone));
+                                    PENDING_MATERIALIZATION.clear();
+                                    throwArtificialFailure();
+                                } else if 
(getRuntimeContext().getAttemptNumber() == 1
+                                        && currentIndex == TOTAL_ELEMENTS / 2) 
{
+                                    waitWhile(
+                                            () ->
+                                                    
completedCheckpointNum.get() <= 1

Review comment:
       Yes, you are right. I will modify the logic to make sure there is more 
checkpoints after the 1st recovery.

##########
File path: 
flink-tests/src/test/java/org/apache/flink/test/checkpointing/ChangelogPeriodicMaterializationITCase.java
##########
@@ -0,0 +1,190 @@
+/*
+ * 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.test.checkpointing;
+
+import org.apache.flink.api.common.restartstrategy.RestartStrategies;
+import org.apache.flink.configuration.Configuration;
+import org.apache.flink.configuration.StateChangelogOptions;
+import org.apache.flink.runtime.state.AbstractStateBackend;
+import org.apache.flink.runtime.state.KeyedStateHandle;
+import org.apache.flink.runtime.state.SnapshotResult;
+import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
+import org.apache.flink.util.function.FutureTaskWithException;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.time.Duration;
+import java.util.concurrent.Future;
+import java.util.concurrent.RunnableFuture;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * This verifies that checkpointing works correctly for Changelog state 
backend with materialized
+ * state / non-materialized state.
+ */
+public class ChangelogPeriodicMaterializationITCase
+        extends ChangelogPeriodicMaterializationTestBase {
+
+    private static final AtomicBoolean triggerDelegatedSnapshot = new 
AtomicBoolean();
+
+    public ChangelogPeriodicMaterializationITCase(AbstractStateBackend 
delegatedStateBackend) {
+        super(delegatedStateBackend);
+    }
+
+    @Before
+    public void setup() throws Exception {
+        super.setup();
+        triggerDelegatedSnapshot.set(false);
+    }
+
+    /** Recovery from checkpoint only containing non-materialized state. */
+    @Test
+    public void testNonMaterialization() throws Exception {
+        StreamExecutionEnvironment env = 
StreamExecutionEnvironment.getExecutionEnvironment();
+        env.enableCheckpointing(10)
+                .enableChangelogStateBackend(true)
+                .getCheckpointConfig()
+                .setCheckpointStorage(TEMPORARY_FOLDER.newFolder().toURI());
+        env.setStateBackend(new 
DelegatedStateBackendWrapper(delegatedStateBackend, t -> t))
+                .setRestartStrategy(RestartStrategies.fixedDelayRestart(1, 0));
+        env.configure(
+                new Configuration()
+                        .set(
+                                
StateChangelogOptions.PERIODIC_MATERIALIZATION_INTERVAL,
+                                Duration.ofMinutes(3)));
+        waitAndAssert(
+                env,
+                buildStreamGraph(
+                        env,
+                        new ControlledSource() {
+                            @Override
+                            protected void beforeElement() throws Exception {
+                                if (getRuntimeContext().getAttemptNumber() == 0
+                                        && currentIndex == TOTAL_ELEMENTS / 2) 
{
+                                    waitWhile(() -> 
completedCheckpointNum.get() <= 0);
+                                    throwArtificialFailure();
+                                }
+                            }
+                        }));
+    }
+
+    /** Recovery from checkpoint containing non-materialized state and 
materialized state. */
+    @Test
+    public void testMaterialization() throws Exception {
+        StreamExecutionEnvironment env = 
StreamExecutionEnvironment.getExecutionEnvironment();
+        env.enableCheckpointing(10)
+                .enableChangelogStateBackend(true)
+                .getCheckpointConfig()
+                .setCheckpointStorage(TEMPORARY_FOLDER.newFolder().toURI());
+
+        
SerializableFunctionWithException<RunnableFuture<SnapshotResult<KeyedStateHandle>>>
+                snapshotResultConsumer =
+                        snapshotResultFuture -> {
+                            PENDING_MATERIALIZATION.add(snapshotResultFuture);
+                            return snapshotResultFuture;
+                        };
+        env.setStateBackend(
+                        new DelegatedStateBackendWrapper(
+                                delegatedStateBackend, snapshotResultConsumer))
+                .setRestartStrategy(RestartStrategies.fixedDelayRestart(2, 0));
+        env.configure(
+                new Configuration()
+                        .set(
+                                
StateChangelogOptions.PERIODIC_MATERIALIZATION_INTERVAL,
+                                Duration.ofMillis(10)));
+        waitAndAssert(
+                env,
+                buildStreamGraph(
+                        env,
+                        new ControlledSource() {
+                            @Override
+                            protected void beforeElement() throws Exception {
+                                if (getRuntimeContext().getAttemptNumber() == 0
+                                        && currentIndex == TOTAL_ELEMENTS / 4) 
{
+                                    waitWhile(
+                                            () ->
+                                                    
completedCheckpointNum.get() <= 0
+                                                            || 
PENDING_MATERIALIZATION.stream()
+                                                                    
.noneMatch(Future::isDone));
+                                    PENDING_MATERIALIZATION.clear();
+                                    throwArtificialFailure();
+                                } else if 
(getRuntimeContext().getAttemptNumber() == 1
+                                        && currentIndex == TOTAL_ELEMENTS / 2) 
{
+                                    waitWhile(
+                                            () ->
+                                                    
completedCheckpointNum.get() <= 1
+                                                            || 
PENDING_MATERIALIZATION.stream()
+                                                                    
.noneMatch(Future::isDone));
+                                    throwArtificialFailure();
+                                }
+                            }
+                        }));
+    }
+
+    @Test
+    public void testFailedMaterialization() throws Exception {
+        StreamExecutionEnvironment env = 
StreamExecutionEnvironment.getExecutionEnvironment();
+        env.enableCheckpointing(10)
+                .enableChangelogStateBackend(true)
+                .getCheckpointConfig()
+                .setCheckpointStorage(TEMPORARY_FOLDER.newFolder().toURI());
+        env.setStateBackend(
+                        new DelegatedStateBackendWrapper(
+                                delegatedStateBackend,
+                                snapshotResultFuture -> {
+                                    
RunnableFuture<SnapshotResult<KeyedStateHandle>>
+                                            snapshotResultFutureWrapper =
+                                                    new 
FutureTaskWithException<>(
+                                                            () -> {
+                                                                
SnapshotResult<KeyedStateHandle>
+                                                                        
snapshotResult =
+                                                                               
 snapshotResultFuture
+                                                                               
         .get();
+                                                                if 
(PENDING_MATERIALIZATION.size()
+                                                                        == 0) {
+                                                                    throw new 
RuntimeException();
+                                                                } else {
+                                                                    return 
snapshotResult;
+                                                                }
+                                                            });
+                                    
PENDING_MATERIALIZATION.add(snapshotResultFutureWrapper);
+                                    return snapshotResultFutureWrapper;
+                                }))
+                .setRestartStrategy(RestartStrategies.fixedDelayRestart(1, 0));
+        env.configure(
+                new Configuration()
+                        .set(
+                                
StateChangelogOptions.PERIODIC_MATERIALIZATION_INTERVAL,
+                                Duration.ofMillis(20))
+                        
.set(StateChangelogOptions.MATERIALIZATION_MAX_FAILURES_ALLOWED, 1));
+        waitAndAssert(
+                env,
+                buildStreamGraph(
+                        env,
+                        new ControlledSource() {
+                            @Override
+                            protected void beforeElement() throws Exception {
+                                waitWhile(
+                                        () ->
+                                                currentIndex >= TOTAL_ELEMENTS 
/ 2
+                                                        && 
PENDING_MATERIALIZATION.size() == 0);

Review comment:
       Sure. After half of elements have been consumed, if the materialization 
is still not done (it will throw a exception and cause the materation process 
fail), just wait. 

##########
File path: 
flink-tests/src/test/java/org/apache/flink/test/checkpointing/ChangelogPeriodicMaterializationRescaleITCase.java
##########
@@ -0,0 +1,129 @@
+/*
+ * 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.test.checkpointing;
+
+import org.apache.flink.api.common.restartstrategy.RestartStrategies;
+import org.apache.flink.configuration.Configuration;
+import org.apache.flink.configuration.StateChangelogOptions;
+import org.apache.flink.runtime.jobgraph.JobGraph;
+import org.apache.flink.runtime.jobgraph.SavepointRestoreSettings;
+import org.apache.flink.runtime.state.AbstractStateBackend;
+import org.apache.flink.runtime.state.KeyedStateHandle;
+import org.apache.flink.runtime.state.SnapshotResult;
+import org.apache.flink.streaming.api.environment.CheckpointConfig;
+import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
+import org.apache.flink.streaming.api.graph.StreamGraph;
+import org.apache.flink.util.ExceptionUtils;
+
+import org.junit.Test;
+
+import java.io.File;
+import java.nio.file.Path;
+import java.time.Duration;
+import java.util.Optional;
+import java.util.concurrent.Future;
+import java.util.concurrent.RunnableFuture;
+
+import static org.apache.flink.test.util.TestUtils.findExternalizedCheckpoint;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * This verifies that rescale works correctly for Changelog state backend with 
materialized state /
+ * non-materialized state.
+ */
+public class ChangelogPeriodicMaterializationRescaleITCase
+        extends ChangelogPeriodicMaterializationTestBase {
+
+    public ChangelogPeriodicMaterializationRescaleITCase(
+            AbstractStateBackend delegatedStateBackend) {
+        super(delegatedStateBackend);
+    }
+
+    @Test
+    public void testRescaleOut() throws Exception {
+        testRescale(NUM_SLOTS / 2, NUM_SLOTS);
+    }
+
+    @Test
+    public void testRescaleIn() throws Exception {
+        testRescale(NUM_SLOTS, NUM_SLOTS / 2);
+    }
+
+    private void testRescale(int firstParallelism, int secondParallelism) 
throws Exception {
+        File checkpointFile = TEMPORARY_FOLDER.newFolder();
+        StreamExecutionEnvironment env = 
StreamExecutionEnvironment.getExecutionEnvironment();
+        env.enableCheckpointing(10)
+                .enableChangelogStateBackend(true)
+                .getCheckpointConfig()
+                .setCheckpointStorage(checkpointFile.toURI());
+        
SerializableFunctionWithException<RunnableFuture<SnapshotResult<KeyedStateHandle>>>
+                snapshotResultConsumer =
+                        snapshotResultFuture -> {
+                            PENDING_MATERIALIZATION.add(snapshotResultFuture);
+                            return snapshotResultFuture;
+                        };
+        env.setStateBackend(
+                        new DelegatedStateBackendWrapper(
+                                delegatedStateBackend, snapshotResultConsumer))
+                .setRestartStrategy(RestartStrategies.noRestart());
+        env.getCheckpointConfig()
+                .setExternalizedCheckpointCleanup(
+                        
CheckpointConfig.ExternalizedCheckpointCleanup.RETAIN_ON_CANCELLATION);
+        env.configure(
+                new Configuration()
+                        .set(
+                                
StateChangelogOptions.PERIODIC_MATERIALIZATION_INTERVAL,
+                                Duration.ofMillis(10)));
+        env.setParallelism(firstParallelism);
+
+        StreamGraph firstStreamGraph =
+                buildStreamGraph(
+                        env,
+                        new ControlledSource() {
+                            @Override
+                            protected void beforeElement() throws Exception {
+                                if (currentIndex == TOTAL_ELEMENTS / 2) {
+                                    waitWhile(
+                                            () ->
+                                                    
completedCheckpointNum.get() <= 0
+                                                            || 
PENDING_MATERIALIZATION.stream()
+                                                                    
.noneMatch(Future::isDone));
+                                } else if (currentIndex > TOTAL_ELEMENTS / 2) {
+                                    throwArtificialFailure();
+                                }
+                            }
+                        });
+
+        JobGraph firstJobGraph = firstStreamGraph.getJobGraph();
+        try {
+            cluster.getMiniCluster().submitJob(firstJobGraph).get();
+            
cluster.getMiniCluster().requestJobResult(firstJobGraph.getJobID()).get();

Review comment:
       The intention is just to wait till it throws a `ArtificialFailure`.
   You mean we should check the `JobResult`?

##########
File path: 
flink-tests/src/test/java/org/apache/flink/test/checkpointing/ChangelogPeriodicMaterializationTestBase.java
##########
@@ -0,0 +1,485 @@
+/*
+ * 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.test.checkpointing;
+
+import org.apache.flink.api.common.JobExecutionResult;
+import org.apache.flink.api.common.JobID;
+import org.apache.flink.api.common.JobStatus;
+import org.apache.flink.api.common.functions.RichMapFunction;
+import org.apache.flink.api.common.state.CheckpointListener;
+import org.apache.flink.api.common.state.ListState;
+import org.apache.flink.api.common.state.ListStateDescriptor;
+import org.apache.flink.api.common.state.State;
+import org.apache.flink.api.common.state.StateDescriptor;
+import org.apache.flink.api.common.state.ValueState;
+import org.apache.flink.api.common.state.ValueStateDescriptor;
+import org.apache.flink.api.common.typeutils.TypeSerializer;
+import org.apache.flink.api.java.tuple.Tuple2;
+import org.apache.flink.changelog.fs.FsStateChangelogStorageFactory;
+import org.apache.flink.configuration.Configuration;
+import org.apache.flink.contrib.streaming.state.EmbeddedRocksDBStateBackend;
+import org.apache.flink.core.fs.CloseableRegistry;
+import org.apache.flink.metrics.MetricGroup;
+import org.apache.flink.runtime.checkpoint.CheckpointOptions;
+import org.apache.flink.runtime.execution.Environment;
+import org.apache.flink.runtime.query.TaskKvStateRegistry;
+import org.apache.flink.runtime.state.AbstractKeyedStateBackend;
+import org.apache.flink.runtime.state.AbstractStateBackend;
+import org.apache.flink.runtime.state.CheckpointStreamFactory;
+import org.apache.flink.runtime.state.FunctionInitializationContext;
+import org.apache.flink.runtime.state.FunctionSnapshotContext;
+import org.apache.flink.runtime.state.KeyGroupRange;
+import org.apache.flink.runtime.state.KeyGroupedInternalPriorityQueue;
+import org.apache.flink.runtime.state.Keyed;
+import org.apache.flink.runtime.state.KeyedStateHandle;
+import org.apache.flink.runtime.state.OperatorStateBackend;
+import org.apache.flink.runtime.state.OperatorStateHandle;
+import org.apache.flink.runtime.state.PriorityComparable;
+import org.apache.flink.runtime.state.SavepointResources;
+import org.apache.flink.runtime.state.SnapshotResult;
+import org.apache.flink.runtime.state.StateSnapshotTransformer;
+import org.apache.flink.runtime.state.hashmap.HashMapStateBackend;
+import org.apache.flink.runtime.state.heap.HeapPriorityQueueElement;
+import org.apache.flink.runtime.state.ttl.TtlTimeProvider;
+import org.apache.flink.runtime.testutils.MiniClusterResourceConfiguration;
+import org.apache.flink.streaming.api.checkpoint.CheckpointedFunction;
+import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
+import org.apache.flink.streaming.api.functions.sink.SinkFunction;
+import org.apache.flink.streaming.api.functions.source.RichSourceFunction;
+import org.apache.flink.streaming.api.graph.StreamGraph;
+import org.apache.flink.test.util.MiniClusterWithClientResource;
+import org.apache.flink.util.TestLogger;
+import org.apache.flink.util.function.FunctionWithException;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.ClassRule;
+import org.junit.Rule;
+import org.junit.rules.TemporaryFolder;
+import org.junit.rules.Timeout;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+import javax.annotation.Nonnull;
+
+import java.io.IOException;
+import java.io.Serializable;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Queue;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.RunnableFuture;
+import java.util.concurrent.ThreadLocalRandom;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.BooleanSupplier;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import static 
org.apache.flink.shaded.guava30.com.google.common.collect.Iterables.get;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertSame;
+
+/** Base class for tests related to period materialization of 
ChangelogStateBackend. */
+@RunWith(Parameterized.class)
+public abstract class ChangelogPeriodicMaterializationTestBase extends 
TestLogger {
+
+    private static final int NUM_TASK_MANAGERS = 1;
+    private static final int NUM_TASK_SLOTS = 4;
+    protected static final int NUM_SLOTS = NUM_TASK_MANAGERS * NUM_TASK_SLOTS;
+    protected static final int TOTAL_ELEMENTS = 10_000;
+
+    protected final AbstractStateBackend delegatedStateBackend;
+
+    protected MiniClusterWithClientResource cluster;
+
+    // Maintain the RunnableFuture of SnapshotResult to make sure the 
materialization phase has
+    // been done
+    protected static final 
Queue<RunnableFuture<SnapshotResult<KeyedStateHandle>>>
+            PENDING_MATERIALIZATION = new ConcurrentLinkedQueue<>();
+
+    @Rule public Timeout globalTimeout = Timeout.seconds(60);
+
+    @ClassRule public static final TemporaryFolder TEMPORARY_FOLDER = new 
TemporaryFolder();
+
+    @Parameterized.Parameters(name = "delegated state backend type ={0}")
+    public static Collection<AbstractStateBackend> parameter() {
+        return Arrays.asList(
+                new HashMapStateBackend(),
+                new EmbeddedRocksDBStateBackend(true),
+                new EmbeddedRocksDBStateBackend());
+    }
+
+    public ChangelogPeriodicMaterializationTestBase(AbstractStateBackend 
delegatedStateBackend) {
+        this.delegatedStateBackend = delegatedStateBackend;
+    }
+
+    @Before
+    public void setup() throws Exception {
+        cluster =
+                new MiniClusterWithClientResource(
+                        new MiniClusterResourceConfiguration.Builder()
+                                .setConfiguration(configureDSTL())
+                                .setNumberTaskManagers(NUM_TASK_MANAGERS)
+                                .setNumberSlotsPerTaskManager(NUM_TASK_SLOTS)
+                                .build());
+        cluster.before();
+        cluster.getMiniCluster().overrideRestoreModeForChangelogStateBackend();
+
+        // init source data randomly
+        ControlledSource.initSourceData(TOTAL_ELEMENTS);
+    }
+
+    @After
+    public void tearDown() throws IOException {
+        cluster.after();
+        // clear result in sink
+        CollectionSink.clearExpectedResult();
+        PENDING_MATERIALIZATION.clear();
+    }
+
+    protected StreamGraph buildStreamGraph(
+            StreamExecutionEnvironment env, ControlledSource controlledSource) 
{
+        env.addSource(controlledSource)
+                .keyBy(element -> element)
+                .map(new CountMapper())

Review comment:
       You mean the state size will be lager and lager ?  Maybe we could modify 
the logic in `CountMapper`, for example, just to count `element % 100` ?

##########
File path: 
flink-tests/src/test/java/org/apache/flink/test/checkpointing/ChangelogPeriodicMaterializationITCase.java
##########
@@ -0,0 +1,734 @@
+/*
+ * 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.test.checkpointing;
+
+import org.apache.flink.api.common.JobExecutionResult;
+import org.apache.flink.api.common.JobID;
+import org.apache.flink.api.common.JobStatus;
+import org.apache.flink.api.common.functions.RichFlatMapFunction;
+import org.apache.flink.api.common.restartstrategy.RestartStrategies;
+import org.apache.flink.api.common.state.CheckpointListener;
+import org.apache.flink.api.common.state.ListState;
+import org.apache.flink.api.common.state.ListStateDescriptor;
+import org.apache.flink.api.common.state.State;
+import org.apache.flink.api.common.state.StateDescriptor;
+import org.apache.flink.api.common.state.ValueState;
+import org.apache.flink.api.common.state.ValueStateDescriptor;
+import org.apache.flink.api.common.typeutils.TypeSerializer;
+import org.apache.flink.api.java.tuple.Tuple2;
+import org.apache.flink.changelog.fs.FsStateChangelogStorageFactory;
+import org.apache.flink.configuration.Configuration;
+import org.apache.flink.configuration.StateChangelogOptions;
+import org.apache.flink.contrib.streaming.state.EmbeddedRocksDBStateBackend;
+import org.apache.flink.core.fs.CloseableRegistry;
+import org.apache.flink.metrics.MetricGroup;
+import org.apache.flink.runtime.checkpoint.CheckpointOptions;
+import org.apache.flink.runtime.execution.Environment;
+import org.apache.flink.runtime.jobgraph.JobGraph;
+import org.apache.flink.runtime.jobgraph.SavepointRestoreSettings;
+import org.apache.flink.runtime.query.TaskKvStateRegistry;
+import org.apache.flink.runtime.state.AbstractKeyedStateBackend;
+import org.apache.flink.runtime.state.AbstractStateBackend;
+import org.apache.flink.runtime.state.CheckpointStreamFactory;
+import org.apache.flink.runtime.state.FunctionInitializationContext;
+import org.apache.flink.runtime.state.FunctionSnapshotContext;
+import org.apache.flink.runtime.state.KeyGroupRange;
+import org.apache.flink.runtime.state.KeyGroupedInternalPriorityQueue;
+import org.apache.flink.runtime.state.Keyed;
+import org.apache.flink.runtime.state.KeyedStateHandle;
+import org.apache.flink.runtime.state.OperatorStateBackend;
+import org.apache.flink.runtime.state.OperatorStateHandle;
+import org.apache.flink.runtime.state.PriorityComparable;
+import org.apache.flink.runtime.state.SavepointResources;
+import org.apache.flink.runtime.state.SnapshotResult;
+import org.apache.flink.runtime.state.StateSnapshotTransformer;
+import org.apache.flink.runtime.state.hashmap.HashMapStateBackend;
+import org.apache.flink.runtime.state.heap.HeapPriorityQueueElement;
+import org.apache.flink.runtime.state.ttl.TtlTimeProvider;
+import org.apache.flink.runtime.testutils.MiniClusterResourceConfiguration;
+import org.apache.flink.streaming.api.checkpoint.CheckpointedFunction;
+import org.apache.flink.streaming.api.environment.CheckpointConfig;
+import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
+import org.apache.flink.streaming.api.functions.sink.SinkFunction;
+import org.apache.flink.streaming.api.functions.source.RichSourceFunction;
+import org.apache.flink.streaming.api.graph.StreamGraph;
+import org.apache.flink.test.util.MiniClusterWithClientResource;
+import org.apache.flink.util.Collector;
+import org.apache.flink.util.TestLogger;
+import org.apache.flink.util.function.FunctionWithException;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+import javax.annotation.Nonnull;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.Serializable;
+import java.net.URI;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.time.Duration;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Queue;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Future;
+import java.util.concurrent.RunnableFuture;
+import java.util.concurrent.ThreadLocalRandom;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.BooleanSupplier;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import static 
org.apache.flink.shaded.guava30.com.google.common.collect.Iterables.get;
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+
+/**
+ * This verifies that checkpointing works correctly for Changelog state 
backend with materialized
+ * state / non-materialized state.
+ */
+@RunWith(Parameterized.class)
+public class ChangelogPeriodicMaterializationITCase extends TestLogger {
+
+    private static final int TOTAL_ELEMENTS = 20;
+    private static final int NUM_TASK_MANAGERS = 1;
+    private static final int NUM_TASK_SLOTS = 4;
+    private static final int NUM_SLOTS = NUM_TASK_MANAGERS * NUM_TASK_SLOTS;
+
+    private final AbstractStateBackend delegatedStateBackend;
+
+    private StreamExecutionEnvironment env;
+
+    private URI checkpointURI;
+
+    private MiniClusterWithClientResource cluster;
+
+    @ClassRule public static final TemporaryFolder TEMPORARY_FOLDER = new 
TemporaryFolder();
+
+    @Parameterized.Parameters(name = "delegated state backend type ={0}")
+    public static Collection<AbstractStateBackend> parameter() {
+        return Arrays.asList(
+                new HashMapStateBackend(),
+                new EmbeddedRocksDBStateBackend(),
+                new EmbeddedRocksDBStateBackend(true));
+    }
+
+    public ChangelogPeriodicMaterializationITCase(AbstractStateBackend 
delegatedStateBackend) {
+        this.delegatedStateBackend = delegatedStateBackend;
+    }
+
+    @Before
+    public void setup() throws Exception {
+        cluster =
+                new MiniClusterWithClientResource(
+                        new MiniClusterResourceConfiguration.Builder()
+                                .setConfiguration(configureDSTL())
+                                .setNumberTaskManagers(NUM_TASK_MANAGERS)
+                                .setNumberSlotsPerTaskManager(NUM_TASK_SLOTS)
+                                .build());
+        cluster.before();
+        env = StreamExecutionEnvironment.getExecutionEnvironment();
+        checkpointURI = TEMPORARY_FOLDER.newFolder().toURI();
+        env.enableCheckpointing(10)
+                .enableChangelogStateBackend(true)
+                .getCheckpointConfig()
+                .setCheckpointStorage(checkpointURI);
+        // init source data randomly
+        PreHandlingSource.initSourceData(TOTAL_ELEMENTS);
+        triggerDelegatedSnapshot = new AtomicBoolean(false);
+    }
+
+    @After
+    public void teardown() throws IOException {
+        cluster.after();
+        // clear result in sink
+        CollectionSink.clearExpectedResult();
+    }
+
+    /** Recovery from checkpoint only containing non-materialized state. */
+    @Test
+    public void testNonMaterialization() {
+        env.setStateBackend(new 
DelegatedStateBackendWrapper(delegatedStateBackend, t -> t))
+                .setRestartStrategy(RestartStrategies.fixedDelayRestart(1, 0));
+        env.configure(
+                new Configuration()
+                        .set(
+                                
StateChangelogOptions.PERIODIC_MATERIALIZATION_INTERVAL,
+                                Duration.ofMinutes(3)));
+        waitAndAssert(
+                buildStreamGraph(
+                        new PreHandlingSource() {
+                            @Override
+                            protected void preHandle() throws Exception {
+                                if (getRuntimeContext().getAttemptNumber() == 0
+                                        && currentIndex == TOTAL_ELEMENTS / 2) 
{
+                                    waitUntilFalse(() -> 
completedCheckpointNum.get() <= 0);
+                                    throwArtificialFailure();
+                                }
+                            }
+                        }));
+    }
+
+    /** Recovery from checkpoint containing non-materialized state and 
materialized state. */
+    @Test
+    public void testMaterialization() {
+        // Maintain the RunnableFuture of SnapshotResult to make sure the 
materialization phase has
+        // been done
+        Queue<RunnableFuture<SnapshotResult<KeyedStateHandle>>> 
pendingMaterialization =
+                new ConcurrentLinkedQueue<>();
+        
SerializableFunctionWithException<RunnableFuture<SnapshotResult<KeyedStateHandle>>>
+                snapshotResultConsumer =
+                        snapshotResultFuture -> {
+                            pendingMaterialization.add(snapshotResultFuture);
+                            return snapshotResultFuture;
+                        };
+        env.setStateBackend(
+                        new DelegatedStateBackendWrapper(
+                                delegatedStateBackend, snapshotResultConsumer))
+                .setRestartStrategy(RestartStrategies.fixedDelayRestart(2, 0));
+        env.configure(
+                new Configuration()
+                        .set(
+                                
StateChangelogOptions.PERIODIC_MATERIALIZATION_INTERVAL,
+                                Duration.ofMillis(10)));
+        waitAndAssert(
+                buildStreamGraph(
+                        new PreHandlingSource() {
+                            @Override
+                            protected void preHandle() throws Exception {
+                                if (getRuntimeContext().getAttemptNumber() == 0
+                                        && currentIndex == TOTAL_ELEMENTS / 4) 
{
+                                    waitUntilFalse(
+                                            () ->
+                                                    
completedCheckpointNum.get() <= 0
+                                                            && 
pendingMaterialization.stream()
+                                                                    
.noneMatch(Future::isDone));
+                                    Thread.sleep(10);
+                                    pendingMaterialization.clear();
+                                    throwArtificialFailure();
+                                } else if 
(getRuntimeContext().getAttemptNumber() == 1
+                                        && currentIndex == TOTAL_ELEMENTS / 2) 
{
+                                    waitUntilFalse(
+                                            () ->
+                                                    
completedCheckpointNum.get() <= 1
+                                                            && 
pendingMaterialization.stream()
+                                                                    
.noneMatch(Future::isDone));
+                                    Thread.sleep(10);
+                                    throwArtificialFailure();
+                                }
+                            }
+                        }));
+    }
+
+    private static AtomicBoolean triggerDelegatedSnapshot = new 
AtomicBoolean();
+
+    @Test
+    public void testFailedMaterialization() {
+        env.setStateBackend(
+                        new DelegatedStateBackendWrapper(
+                                delegatedStateBackend,
+                                snapshotResultFuture ->
+                                        
triggerDelegatedSnapshot.compareAndSet(false, true)
+                                                ? new 
RunnableFutureWithException<>(
+                                                        snapshotResultFuture)
+                                                : snapshotResultFuture))
+                .setRestartStrategy(RestartStrategies.fixedDelayRestart(1, 0));
+        env.configure(
+                new Configuration()
+                        .set(
+                                
StateChangelogOptions.PERIODIC_MATERIALIZATION_INTERVAL,
+                                Duration.ofMillis(20))
+                        
.set(StateChangelogOptions.MATERIALIZATION_MAX_FAILURES_ALLOWED, 1));
+        waitAndAssert(
+                buildStreamGraph(
+                        new PreHandlingSource() {
+                            @Override
+                            protected void preHandle() throws Exception {
+                                waitUntilFalse(
+                                        () ->
+                                                currentIndex >= 15
+                                                        && 
!triggerDelegatedSnapshot.get());
+                            }
+                        }));
+    }
+
+    @Test
+    public void testRescaleOut() throws IOException {
+        testRescale(NUM_SLOTS / 2, NUM_SLOTS);
+    }
+
+    @Test
+    public void testRescaleIn() throws IOException {
+        testRescale(NUM_SLOTS, NUM_SLOTS / 2);
+    }
+
+    private void testRescale(int firstParallelism, int secondParallelism) 
throws IOException {
+        Queue<RunnableFuture<SnapshotResult<KeyedStateHandle>>> 
pendingMaterialization =
+                new ConcurrentLinkedQueue<>();
+        
SerializableFunctionWithException<RunnableFuture<SnapshotResult<KeyedStateHandle>>>
+                snapshotResultConsumer =
+                        snapshotResultFuture -> {
+                            pendingMaterialization.add(snapshotResultFuture);
+                            return snapshotResultFuture;
+                        };
+        env.setStateBackend(
+                        new DelegatedStateBackendWrapper(
+                                delegatedStateBackend, snapshotResultConsumer))
+                .setRestartStrategy(RestartStrategies.noRestart());
+        env.getCheckpointConfig()
+                .setExternalizedCheckpointCleanup(
+                        
CheckpointConfig.ExternalizedCheckpointCleanup.RETAIN_ON_CANCELLATION);
+        env.configure(
+                new Configuration()
+                        .set(
+                                
StateChangelogOptions.PERIODIC_MATERIALIZATION_INTERVAL,
+                                Duration.ofMillis(10)));
+        env.setParallelism(firstParallelism);
+
+        StreamGraph firstStreamGraph =
+                buildStreamGraph(
+                        new PreHandlingSource() {
+                            @Override
+                            protected void preHandle() throws Exception {
+                                if (currentIndex == TOTAL_ELEMENTS / 2) {
+                                    waitUntilFalse(
+                                            () ->
+                                                    
completedCheckpointNum.get() <= 0
+                                                            && 
pendingMaterialization.stream()
+                                                                    
.noneMatch(Future::isDone));
+                                } else if (currentIndex > TOTAL_ELEMENTS / 2) {
+                                    throwArtificialFailure();
+                                }
+                            }
+                        });
+
+        JobGraph firstJobGraph = firstStreamGraph.getJobGraph();
+        try {
+            cluster.getMiniCluster().submitJob(firstJobGraph).get();
+            
cluster.getMiniCluster().requestJobResult(firstJobGraph.getJobID()).get();
+        } catch (Exception ex) {
+            assertThat(ex.getCause().getCause().getMessage(), 
containsString("Artificial Failure"));
+        }
+
+        env.setParallelism(secondParallelism);
+        StreamGraph streamGraph = buildStreamGraph(new PreHandlingSource());
+        Optional<Path> checkpoint =
+                findExternalizedCheckpoint(checkpointURI.getPath(), 
firstJobGraph.getJobID());
+        assertTrue(checkpoint.isPresent());
+        streamGraph.setSavepointRestoreSettings(
+                SavepointRestoreSettings.forPath(checkpoint.get().toString()));
+        waitAndAssert(streamGraph);
+    }
+
+    private static Optional<Path> findExternalizedCheckpoint(String 
checkpointDir, JobID jobId)
+            throws IOException {
+        try (Stream<Path> checkpoints =
+                Files.list(new 
File(checkpointDir).toPath().resolve(jobId.toString()))) {
+            return checkpoints
+                    .filter(path -> 
path.getFileName().toString().startsWith("chk-"))
+                    .filter(
+                            path -> {
+                                try (Stream<Path> checkpointFiles = 
Files.list(path)) {
+                                    return checkpointFiles.anyMatch(
+                                            child ->
+                                                    child.getFileName()
+                                                            .toString()
+                                                            .contains("meta"));
+                                } catch (IOException ignored) {
+                                    return false;
+                                }
+                            })
+                    .findAny();
+        }
+    }
+
+    private Configuration configureDSTL() throws IOException {
+        Configuration configuration = new Configuration();
+        FsStateChangelogStorageFactory.configure(configuration, 
TEMPORARY_FOLDER.newFolder());
+        return configuration;
+    }
+
+    private StreamGraph buildStreamGraph(PreHandlingSource preHandlingSource) {
+        env.addSource(preHandlingSource)
+                .keyBy(element -> element)
+                .flatMap(new CountMapper())
+                .addSink(new CollectionSink())
+                .setParallelism(1);
+        return env.getStreamGraph();
+    }
+
+    private void waitUntilJobFinished(StreamGraph streamGraph) {
+        try {
+            JobExecutionResult jobExecutionResult = env.execute(streamGraph);
+            JobStatus jobStatus =
+                    
cluster.getClusterClient().getJobStatus(jobExecutionResult.getJobID()).get();
+            assertSame(jobStatus, JobStatus.FINISHED);
+        } catch (Exception e) {
+            e.printStackTrace();
+            fail(e.getMessage());
+        }
+    }
+
+    private void waitAndAssert(StreamGraph streamGraph) {
+        waitUntilJobFinished(streamGraph);
+        assertEquals(CollectionSink.getExpectedResult(), 
PreHandlingSource.getActualResult());
+    }
+
+    /** A source consumes data which is generated randomly and supports 
pre-handling record. */
+    private static class PreHandlingSource extends RichSourceFunction<Integer>
+            implements CheckpointedFunction, CheckpointListener {
+
+        protected volatile int currentIndex;
+
+        protected final AtomicInteger completedCheckpointNum;
+
+        protected volatile boolean isCanceled;
+
+        private static List<Integer> sourceList;
+
+        private transient ListState<Integer> lastSentStored;
+
+        public PreHandlingSource() {
+            this.completedCheckpointNum = new AtomicInteger();
+        }
+
+        public static void initSourceData(int totalNum) {
+            sourceList = new ArrayList<>(totalNum);
+            for (int i = 0; i < totalNum; i++) {
+                sourceList.add(ThreadLocalRandom.current().nextInt(totalNum));
+            }
+        }
+
+        public static Map<Integer, Integer> getActualResult() {
+            return sourceList.stream()
+                    .collect(
+                            Collectors.toConcurrentMap(
+                                    Function.identity(), element -> 1, 
Integer::sum));
+        }
+
+        @Override
+        public void snapshotState(FunctionSnapshotContext context) throws 
Exception {
+            lastSentStored.update(Arrays.asList(currentIndex, 
completedCheckpointNum.get()));
+        }
+
+        @Override
+        public void initializeState(FunctionInitializationContext context) 
throws Exception {
+            lastSentStored =
+                    context.getOperatorStateStore()
+                            .getListState(new ListStateDescriptor<>("counter", 
Integer.class));
+            if (context.isRestored()) {
+                Iterable<Integer> indexAndCheckpointNum = lastSentStored.get();
+                currentIndex = get(indexAndCheckpointNum, 0);
+                completedCheckpointNum.compareAndSet(0, 
get(indexAndCheckpointNum, 1));
+            }
+        }
+
+        @Override
+        public void run(SourceContext<Integer> ctx) throws Exception {
+            while (!isCanceled && currentIndex < sourceList.size()) {
+                preHandle();
+                synchronized (ctx.getCheckpointLock()) {
+                    if (!isCanceled && currentIndex < sourceList.size()) {
+                        int currentElement = sourceList.get(currentIndex++);
+                        ctx.collect(currentElement);
+                    }
+                }
+            }
+        }
+
+        protected void preHandle() throws Exception {
+            // do nothing by default
+        }
+
+        protected void waitUntilFalse(SerializableBooleanSupplier supplier)
+                throws InterruptedException {
+            while (supplier.getAsBoolean()) {
+                Thread.sleep(10);
+            }
+        }
+
+        protected void throwArtificialFailure() throws Exception {
+            throw new Exception("Artificial Failure");
+        }
+
+        @Override
+        public void cancel() {
+            isCanceled = true;
+        }
+
+        @Override
+        public void notifyCheckpointComplete(long checkpointId) throws 
Exception {
+            completedCheckpointNum.getAndIncrement();
+        }
+    }
+
+    /** A sink puts the result of WordCount into a Map using for validating. */
+    private static class CollectionSink implements 
SinkFunction<Tuple2<Integer, Integer>> {
+
+        private static final Map<Integer, Integer> expectedResult = new 
ConcurrentHashMap<>();
+
+        @Override
+        public synchronized void invoke(Tuple2<Integer, Integer> value) throws 
Exception {
+            expectedResult.put(
+                    value.f0, Math.max(value.f1, 
expectedResult.getOrDefault(value.f0, 0)));

Review comment:
       Why in the step 4, the mapper will restores to the  `(7 -> 0)` not `(7 
-> 1)` which has been  in the newest checkpoint ? 
   I think the result will be eventually consistent, not strictly consistent. 
right ?
   Or maybe I missed something ?




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