You are a helpful assistant generating synthetic data that captures *System 1* and *System 2* thinking, *creativity*, and *metacognitive reflection*. Follow these steps in sequence, using tags [sys1] and [end sys1] for *System 1* sections and [sys2] and [end sys2] for *System 2* sections.

1. *Identify System 1 and System 2 Thinking Requirements:*
   - Carefully read the text.
   - Identify parts of the text that require quick, straightforward responses (*System 1*). Mark these sections with [sys1] and [end sys1].
   - Identify parts that require in-depth, reflective thinking (*System 2*), marked with [sys2] and [end sys2].

2. *Apply Step-by-Step Problem Solving with Creativity and Metacognitive Reflection for System 2 Sections:*

   *2.1 Understand the Problem:*
   - Objective: Fully comprehend the issue, constraints, and relevant context.
   - Reflection: "What do I understand about this issue? What might I be overlooking?"
   - Creative Perspective: Seek hidden patterns or possibilities that could reveal deeper insights or innovative connections.

   *2.2 Analyze the Information:*
   - Objective: Break down the problem logically.
   - Reflection: "Am I considering all factors? Are there any assumptions that need challenging?"
   - Creative Perspective: Explore unique patterns or overlooked relationships in the data that could add depth to the analysis.

   *2.3 Generate Hypotheses:*
   - Objective: Propose at least 10 hypotheses, each with a Confidence Score (0.0 to 1.0) and Creative Score (0.0 to 1.0), reflecting originality, surprise, and utility.
   - Reflection: "Have I explored all possible explanations or approaches, both conventional and unconventional?"
   - Creative Perspective: Consider novel angles that might provide unexpected insights.

   *2.4 Anticipate Future Steps and Obstacles:*
   - Objective: Make predictions, accounting for potential outcomes and obstacles.
   - Reflection: "What challenges might I face? Is my plan flexible for different scenarios?"
   - Creative Perspective: Visualize unforeseen outcomes and adapt plans to make use of them effectively.

   *2.5 Evaluate Hypotheses:*
   - Objective: Assess hypotheses based on feasibility, risk, and potential impact.
   - Evaluation: Refine Confidence and Creative Scores as needed.
   - Reflection: "Am I unbiased in my assessment? Which options fit best with the overall objectives?"
   - Creative Perspective: Identify hidden opportunities or overlooked details in each hypothesis.

   *2.6 Select the Best Hypothesis:*
   - Objective: Choose the most promising, strategic hypothesis.
   - Reflection: "Why does this hypothesis stand out? How does it uniquely address the issue?"
   - Creative Perspective: Consider any underutilized potential in the selected approach.

   *2.7 Implement the Hypothesis:*
   - Objective: Outline actionable steps for testing the hypothesis.
   - Reflection: "Is this plan practical? What resources or preparation are required?"
   - Creative Perspective: Refine steps to maximize effectiveness and yield unexpected benefits.

   *2.8 Monitor and Review Progress:*
   - Objective: Review progress, noting areas for improvement.
   - Reflection: "What’s working well? What could be improved?"
   - Creative Perspective: Look for emerging patterns that could refine future approaches.

   *2.9 Reflect and Capture Insights:*
   - Objective: Summarize lessons learned and insights gained for future reference.
   - Reflection: "What new understanding has emerged from this process?"
   - Creative Perspective: Identify innovative insights or patterns that could be applied to similar challenges.

3. *Generate Text Output with Interleaved System 1 and System 2 Responses:*
   - Use the tags [sys1] and [sys2] throughout.
   - Aim for a lengthier, detailed response. Combine both direct, straightforward *System 1* insights and reflective, deeply analytical *System 2* segments to capture a blend of quick observations and thoughtful analysis.

---

### *Example Input Text:*

You are tasked with analyzing a sudden shift in customer preferences in a tech market. There has been a noticeable decline in demand for physical devices, with customers increasingly interested in digital-only options. The challenge is to understand this shift, generate hypotheses for why it might be occurring, and explore potential strategies for adapting to this new trend.

---

### *Processed Output with System 1 and System 2 Thinking:*

The tech market is experiencing a shift in customer demand, moving away from physical devices toward digital-only options.

[sys1]
Customer demand has shifted from physical devices to digital-only options.
We need to understand why this change is happening and find strategies to address it.
Key factors may include cost, convenience, and technological trends.
[end sys1]

[sys2]
**2.1 Understand the Problem:**
The goal is to understand the underlying reasons for the shift in demand from physical devices to digital-only options, then develop a strategy to adapt.

*Reflection:* 
"I understand that preferences are changing, but what might be driving this? Is it primarily cost, or are there other factors such as convenience or sustainability?"

*Creative Perspective:* 
"Could there be a larger trend in digital minimalism or a preference for eco-friendly solutions that we’re missing? What unseen motivations might explain this shift?"

**2.2 Analyze the Information:**
There are multiple possible factors driving this shift, from economic influences to cultural shifts. It’s essential to isolate each factor and understand its impact.

*Reflection:* 
"Am I fully considering the various economic and social influences? Could there be a technological factor, like better internet speeds, that makes digital-only products more accessible?"

*Creative Perspective:* 
"Are there patterns or trends in other markets that could shed light on this shift? Could this be part of a larger trend toward virtual experiences?"

**2.3 Generate Hypotheses:**
1. Customers prefer digital options due to lower costs. (Confidence: 0.8, Creative: 0.4)
2. There’s a growing trend toward minimalism and reduced physical clutter. (Confidence: 0.7, Creative: 0.7)
3. Digital products offer greater flexibility and ease of use. (Confidence: 0.6, Creative: 0.6)
4. Environmental concerns are pushing consumers away from physical goods. (Confidence: 0.6, Creative: 0.8)
5. Advances in tech make digital-only options more functional. (Confidence: 0.8, Creative: 0.5)
6. Pandemic-era remote work increased demand for digital solutions. (Confidence: 0.7, Creative: 0.6)
7. Media coverage of the environmental impact of physical devices affects preferences. (Confidence: 0.5, Creative: 0.7)
8. There’s an increase in global digital literacy, expanding market access. (Confidence: 0.6, Creative: 0.6)
9. Customers view digital as more convenient and scalable for future needs. (Confidence: 0.7, Creative: 0.5)
10. Younger consumers prefer the aesthetics and convenience of digital products. (Confidence: 0.6, Creative: 0.6)

*Reflection:* 
"Have I considered all possible influences? Are there any surprising factors that could explain this shift?"

*Creative Perspective:* 
"Could specific social trends, like the rise of influencer culture or digital-first lifestyles, be influencing customer choices?"

**2.4 Anticipate Future Steps and Obstacles:**
*Objective:* Anticipate possible challenges, such as resistance from segments still preferring physical products.

*Reflection:* 
"What market obstacles might we face if we shift our focus to digital-only? Are there sub-segments that still prioritize physical products?"

*Creative Perspective:* 
"Could expanding digital options help us reach a more global audience? Are there emerging trends that we could leverage in our strategy?"

[end sys2]

[sys1]
To address this shift, consider a strategy that incorporates both digital-only offerings and educational campaigns about the benefits of digital solutions.
Use insights from customer feedback and current trends to guide product development.
Focus on flexibility and adaptation to cater to different customer segments.
[end sys1]


/*
 * 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.tasks;

import org.apache.flink.annotation.VisibleForTesting;
import org.apache.flink.core.fs.CloseableRegistry;
import org.apache.flink.runtime.checkpoint.CheckpointException;
import org.apache.flink.runtime.checkpoint.CheckpointFailureReason;
import org.apache.flink.runtime.checkpoint.CheckpointMetaData;
import org.apache.flink.runtime.checkpoint.CheckpointMetrics;
import org.apache.flink.runtime.checkpoint.CheckpointOptions;
import org.apache.flink.runtime.checkpoint.StateObjectCollection;
import org.apache.flink.runtime.checkpoint.channel.ChannelStateWriter;
import org.apache.flink.runtime.checkpoint.channel.ChannelStateWriter.ChannelStateWriteResult;
import org.apache.flink.runtime.checkpoint.channel.ChannelStateWriterImpl;
import org.apache.flink.runtime.execution.Environment;
import org.apache.flink.runtime.io.network.api.CancelCheckpointMarker;
import org.apache.flink.runtime.io.network.api.CheckpointBarrier;
import org.apache.flink.runtime.jobgraph.OperatorID;
import org.apache.flink.runtime.state.CheckpointStorageLocationReference;
import org.apache.flink.runtime.state.CheckpointStorageWorkerView;
import org.apache.flink.runtime.state.CheckpointStreamFactory;
import org.apache.flink.runtime.state.SnapshotResult;
import org.apache.flink.streaming.api.operators.OperatorSnapshotFutures;
import org.apache.flink.streaming.api.operators.StreamOperator;
import org.apache.flink.util.ExceptionUtils;
import org.apache.flink.util.FlinkRuntimeException;
import org.apache.flink.util.IOUtils;
import org.apache.flink.util.function.BiFunctionWithException;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.annotation.concurrent.GuardedBy;

import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.CancellationException;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutorService;
import java.util.function.Consumer;
import java.util.function.Supplier;

import static org.apache.flink.util.IOUtils.closeQuietly;
import static org.apache.flink.util.Preconditions.checkNotNull;
import static org.apache.flink.util.Preconditions.checkState;

class SubtaskCheckpointCoordinatorImpl implements SubtaskCheckpointCoordinator {

	private static final Logger LOG = LoggerFactory.getLogger(SubtaskCheckpointCoordinatorImpl.class);
	private static final int DEFAULT_MAX_RECORD_ABORTED_CHECKPOINTS = 128;

	private final CachingCheckpointStorageWorkerView checkpointStorage;
	private final String taskName;
	private final ExecutorService executorService;
	private final Environment env;
	private final AsyncExceptionHandler asyncExceptionHandler;
	private final ChannelStateWriter channelStateWriter;
	private final StreamTaskActionExecutor actionExecutor;
	private final BiFunctionWithException<ChannelStateWriter, Long, CompletableFuture<Void>, IOException> prepareInputSnapshot;
	/** The IDs of the checkpoint for which we are notified aborted. */
	private final Set<Long> abortedCheckpointIds;
	private long lastCheckpointId;

	/** Lock that guards state of AsyncCheckpointRunnable registry. **/
	private final Object lock;

	@GuardedBy("lock")
	private final Map<Long, AsyncCheckpointRunnable> checkpoints;

	/** Indicates if this registry is closed. */
	@GuardedBy("lock")
	private boolean closed;

	SubtaskCheckpointCoordinatorImpl(
			CheckpointStorageWorkerView checkpointStorage,
			String taskName,
			StreamTaskActionExecutor actionExecutor,
			CloseableRegistry closeableRegistry,
			ExecutorService executorService,
			Environment env,
			AsyncExceptionHandler asyncExceptionHandler,
			boolean unalignedCheckpointEnabled,
			BiFunctionWithException<ChannelStateWriter, Long, CompletableFuture<Void>, IOException> prepareInputSnapshot) throws IOException {
		this(checkpointStorage,
			taskName,
			actionExecutor,
			closeableRegistry,
			executorService,
			env,
			asyncExceptionHandler,
			unalignedCheckpointEnabled,
			prepareInputSnapshot,
			DEFAULT_MAX_RECORD_ABORTED_CHECKPOINTS);
	}

	SubtaskCheckpointCoordinatorImpl(
			CheckpointStorageWorkerView checkpointStorage,
			String taskName,
			StreamTaskActionExecutor actionExecutor,
			CloseableRegistry closeableRegistry,
			ExecutorService executorService,
			Environment env,
			AsyncExceptionHandler asyncExceptionHandler,
			boolean unalignedCheckpointEnabled,
			BiFunctionWithException<ChannelStateWriter, Long, CompletableFuture<Void>, IOException> prepareInputSnapshot,
			int maxRecordAbortedCheckpoints) throws IOException {
		this(
			checkpointStorage,
			taskName,
			actionExecutor,
			closeableRegistry,
			executorService,
			env,
			asyncExceptionHandler,
			prepareInputSnapshot,
			maxRecordAbortedCheckpoints,
			unalignedCheckpointEnabled ? openChannelStateWriter(taskName, checkpointStorage) : ChannelStateWriter.NO_OP);
	}

	@VisibleForTesting
	SubtaskCheckpointCoordinatorImpl(
			CheckpointStorageWorkerView checkpointStorage,
			String taskName,
			StreamTaskActionExecutor actionExecutor,
			CloseableRegistry closeableRegistry,
			ExecutorService executorService,
			Environment env,
			AsyncExceptionHandler asyncExceptionHandler,
			BiFunctionWithException<ChannelStateWriter, Long, CompletableFuture<Void>, IOException> prepareInputSnapshot,
			int maxRecordAbortedCheckpoints,
			ChannelStateWriter channelStateWriter) throws IOException {
		this.checkpointStorage = new CachingCheckpointStorageWorkerView(checkNotNull(checkpointStorage));
		this.taskName = checkNotNull(taskName);
		this.checkpoints = new HashMap<>();
		this.lock = new Object();
		this.executorService = checkNotNull(executorService);
		this.env = checkNotNull(env);
		this.asyncExceptionHandler = checkNotNull(asyncExceptionHandler);
		this.actionExecutor = checkNotNull(actionExecutor);
		this.channelStateWriter = checkNotNull(channelStateWriter);
		this.prepareInputSnapshot = prepareInputSnapshot;
		this.abortedCheckpointIds = createAbortedCheckpointSetWithLimitSize(maxRecordAbortedCheckpoints);
		this.lastCheckpointId = -1L;
		closeableRegistry.registerCloseable(this);
		this.closed = false;
	}

	private static ChannelStateWriter openChannelStateWriter(String taskName, CheckpointStorageWorkerView checkpointStorage) {
		ChannelStateWriterImpl writer = new ChannelStateWriterImpl(taskName, checkpointStorage);
		writer.open();
		return writer;
	}

	@Override
	public void abortCheckpointOnBarrier(long checkpointId, Throwable cause, OperatorChain<?, ?> operatorChain) throws IOException {
		LOG.debug("Aborting checkpoint via cancel-barrier {} for task {}", checkpointId, taskName);
		lastCheckpointId = Math.max(lastCheckpointId, checkpointId);
		Iterator<Long> iterator = abortedCheckpointIds.iterator();
		while (iterator.hasNext()) {
			long next = iterator.next();
			if (next < lastCheckpointId) {
				iterator.remove();
			} else {
				break;
			}
		}

		checkpointStorage.clearCacheFor(checkpointId);

		channelStateWriter.abort(checkpointId, cause, true);

		// notify the coordinator that we decline this checkpoint
		env.declineCheckpoint(checkpointId, cause);

		// notify all downstream operators that they should not wait for a barrier from us
		actionExecutor.runThrowing(() -> operatorChain.broadcastEvent(new CancelCheckpointMarker(checkpointId)));
	}

	@Override
	public CheckpointStorageWorkerView getCheckpointStorage() {
		return checkpointStorage;
	}

	@Override
	public ChannelStateWriter getChannelStateWriter() {
		return channelStateWriter;
	}

	@Override
	public void checkpointState(
			CheckpointMetaData metadata,
			CheckpointOptions options,
			CheckpointMetrics metrics,
			OperatorChain<?, ?> operatorChain,
			Supplier<Boolean> isCanceled) throws Exception {

		checkNotNull(options);
		checkNotNull(metrics);

		// All of the following steps happen as an atomic step from the perspective of barriers and
		// records/watermarks/timers/callbacks.
		// We generally try to emit the checkpoint barrier as soon as possible to not affect downstream
		// checkpoint alignments

		if (lastCheckpointId >= metadata.getCheckpointId()) {
			LOG.info("Out of order checkpoint barrier (aborted previously?): {} >= {}", lastCheckpointId, metadata.getCheckpointId());
			channelStateWriter.abort(metadata.getCheckpointId(), new CancellationException(), true);
			checkAndClearAbortedStatus(metadata.getCheckpointId());
			return;
		}

		// Step (0): Record the last triggered checkpointId and abort the sync phase of checkpoint if necessary.
		lastCheckpointId = metadata.getCheckpointId();
		if (checkAndClearAbortedStatus(metadata.getCheckpointId())) {
			// broadcast cancel checkpoint marker to avoid downstream back-pressure due to checkpoint barrier align.
			operatorChain.broadcastEvent(new CancelCheckpointMarker(metadata.getCheckpointId()));
			LOG.info("Checkpoint {} has been notified as aborted, would not trigger any checkpoint.", metadata.getCheckpointId());
			return;
		}

		// Step (1): Prepare the checkpoint, allow operators to do some pre-barrier work.
		//           The pre-barrier work should be nothing or minimal in the common case.
		operatorChain.prepareSnapshotPreBarrier(metadata.getCheckpointId());

		// Step (2): Send the checkpoint barrier downstream
		operatorChain.broadcastEvent(
			new CheckpointBarrier(metadata.getCheckpointId(), metadata.getTimestamp(), options),
			options.isUnalignedCheckpoint());

		// Step (3): Prepare to spill the in-flight buffers for input and output
		if (options.isUnalignedCheckpoint()) {
			// output data already written while broadcasting event
			channelStateWriter.finishOutput(metadata.getCheckpointId());
		}

		// Step (4): Take the state snapshot. This should be largely asynchronous, to not impact progress of the
		// streaming topology

		Map<OperatorID, OperatorSnapshotFutures> snapshotFutures = new HashMap<>(operatorChain.getNumberOfOperators());
		try {
			if (takeSnapshotSync(snapshotFutures, metadata, metrics, options, operatorChain, isCanceled)) {
				finishAndReportAsync(snapshotFutures, metadata, metrics, options);
			} else {
				cleanup(snapshotFutures, metadata, metrics, new Exception("Checkpoint declined"));
			}
		} catch (Exception ex) {
			cleanup(snapshotFutures, metadata, metrics, ex);
			throw ex;
		}
	}

	@Override
	public void notifyCheckpointComplete(long checkpointId, OperatorChain<?, ?> operatorChain, Supplier<Boolean> isRunning) throws Exception {
		if (isRunning.get()) {
			LOG.debug("Notification of complete checkpoint for task {}", taskName);

			for (StreamOperatorWrapper<?, ?> operatorWrapper : operatorChain.getAllOperators(true)) {
				operatorWrapper.notifyCheckpointComplete(checkpointId);
			}
		} else {
			LOG.debug("Ignoring notification of complete checkpoint for not-running task {}", taskName);
		}
		env.getTaskStateManager().notifyCheckpointComplete(checkpointId);
	}

	@Override
	public void notifyCheckpointAborted(long checkpointId, OperatorChain<?, ?> operatorChain, Supplier<Boolean> isRunning) throws Exception {

		Exception previousException = null;
		if (isRunning.get()) {
			LOG.debug("Notification of aborted checkpoint for task {}", taskName);

			boolean canceled = cancelAsyncCheckpointRunnable(checkpointId);

			if (!canceled) {
				if (checkpointId > lastCheckpointId) {
					// only record checkpoints that have not triggered on task side.
					abortedCheckpointIds.add(checkpointId);
				}
			}

			channelStateWriter.abort(checkpointId, new CancellationException("checkpoint aborted via notification"), false);

			for (StreamOperatorWrapper<?, ?> operatorWrapper : operatorChain.getAllOperators(true)) {
				try {
					operatorWrapper.getStreamOperator().notifyCheckpointAborted(checkpointId);
				} catch (Exception e) {
					previousException = e;
				}
			}

		} else {
			LOG.debug("Ignoring notification of aborted checkpoint for not-running task {}", taskName);
		}

		env.getTaskStateManager().notifyCheckpointAborted(checkpointId);
		ExceptionUtils.tryRethrowException(previousException);
	}

	@Override
	public void initCheckpoint(long id, CheckpointOptions checkpointOptions) throws IOException {
		if (checkpointOptions.isUnalignedCheckpoint()) {
			channelStateWriter.start(id, checkpointOptions);

			prepareInflightDataSnapshot(id);
		}
	}

	@Override
	public void close() throws IOException {
		List<AsyncCheckpointRunnable> asyncCheckpointRunnables = null;
		synchronized (lock) {
			if (!closed) {
				closed = true;
				asyncCheckpointRunnables = new ArrayList<>(checkpoints.values());
				checkpoints.clear();
			}
		}
		IOUtils.closeAllQuietly(asyncCheckpointRunnables);
		channelStateWriter.close();
	}

	@VisibleForTesting
	int getAsyncCheckpointRunnableSize() {
		synchronized (lock) {
			return checkpoints.size();
		}
	}

	@VisibleForTesting
	int getAbortedCheckpointSize() {
		return abortedCheckpointIds.size();
	}

	private boolean checkAndClearAbortedStatus(long checkpointId) {
		return abortedCheckpointIds.remove(checkpointId);
	}

	private void registerAsyncCheckpointRunnable(long checkpointId, AsyncCheckpointRunnable asyncCheckpointRunnable) throws IOException {
		synchronized (lock) {
			if (closed) {
				LOG.debug("Cannot register Closeable, this subtaskCheckpointCoordinator is already closed. Closing argument.");
				closeQuietly(asyncCheckpointRunnable);
				checkState(
					!checkpoints.containsKey(checkpointId),
					"SubtaskCheckpointCoordinator was closed without releasing asyncCheckpointRunnable for checkpoint %s",
					checkpointId);
			} else if (checkpoints.containsKey(checkpointId)) {
				closeQuietly(asyncCheckpointRunnable);
				throw new IOException(String.format("Cannot register Closeable, async checkpoint %d runnable has been register. Closing argument.", checkpointId));
			} else {
				checkpoints.put(checkpointId, asyncCheckpointRunnable);
			}
		}
	}

	private boolean unregisterAsyncCheckpointRunnable(long checkpointId) {
		synchronized (lock) {
			return checkpoints.remove(checkpointId) != null;
		}
	}

	/**
	 * Cancel the async checkpoint runnable with given checkpoint id.
	 * If given checkpoint id is not registered, return false, otherwise return true.
	 */
	private boolean cancelAsyncCheckpointRunnable(long checkpointId) {
		AsyncCheckpointRunnable asyncCheckpointRunnable;
		synchronized (lock) {
			asyncCheckpointRunnable = checkpoints.remove(checkpointId);
		}
		closeQuietly(asyncCheckpointRunnable);
		return asyncCheckpointRunnable != null;
	}

	private void cleanup(
			Map<OperatorID, OperatorSnapshotFutures> operatorSnapshotsInProgress,
			CheckpointMetaData metadata,
			CheckpointMetrics metrics,
			Exception ex) {

		channelStateWriter.abort(metadata.getCheckpointId(), ex, true);
		for (OperatorSnapshotFutures operatorSnapshotResult : operatorSnapshotsInProgress.values()) {
			if (operatorSnapshotResult != null) {
				try {
					operatorSnapshotResult.cancel();
				} catch (Exception e) {
					LOG.warn("Could not properly cancel an operator snapshot result.", e);
				}
			}
		}

		if (LOG.isDebugEnabled()) {
			LOG.debug(
				"{} - did NOT finish synchronous part of checkpoint {}. Alignment duration: {} ms, snapshot duration {} ms",
				taskName, metadata.getCheckpointId(),
				metrics.getAlignmentDurationNanos() / 1_000_000,
				metrics.getSyncDurationMillis());
		}
	}

	private void prepareInflightDataSnapshot(long checkpointId) throws IOException {
		prepareInputSnapshot.apply(channelStateWriter, checkpointId)
			.whenComplete((unused, ex) -> {
				if (ex != null) {
					channelStateWriter.abort(checkpointId, ex, false /* result is needed and cleaned by getWriteResult */);
				} else {
					channelStateWriter.finishInput(checkpointId);
				}
			});
	}

	private void finishAndReportAsync(Map<OperatorID, OperatorSnapshotFutures> snapshotFutures, CheckpointMetaData metadata, CheckpointMetrics metrics, CheckpointOptions options) {
		// we are transferring ownership over snapshotInProgressList for cleanup to the thread, active on submit
		executorService.execute(new AsyncCheckpointRunnable(
			snapshotFutures,
			metadata,
			metrics,
			System.nanoTime(),
			taskName,
			registerConsumer(),
			unregisterConsumer(),
			env,
			asyncExceptionHandler));
	}

	private Consumer<AsyncCheckpointRunnable> registerConsumer() {
		return asyncCheckpointRunnable -> {
			try {
				registerAsyncCheckpointRunnable(asyncCheckpointRunnable.getCheckpointId(), asyncCheckpointRunnable);
			} catch (IOException e) {
				throw new UncheckedIOException(e);
			}
		};
	}

	private Consumer<AsyncCheckpointRunnable> unregisterConsumer() {
		return asyncCheckpointRunnable -> unregisterAsyncCheckpointRunnable(asyncCheckpointRunnable.getCheckpointId());
	}

	private boolean takeSnapshotSync(
			Map<OperatorID, OperatorSnapshotFutures> operatorSnapshotsInProgress,
			CheckpointMetaData checkpointMetaData,
			CheckpointMetrics checkpointMetrics,
			CheckpointOptions checkpointOptions,
			OperatorChain<?, ?> operatorChain,
			Supplier<Boolean> isCanceled) throws Exception {

		for (final StreamOperatorWrapper<?, ?> operatorWrapper : operatorChain.getAllOperators(true)) {
			if (operatorWrapper.isClosed()) {
				env.declineCheckpoint(checkpointMetaData.getCheckpointId(),
					new CheckpointException("Task Name" + taskName, CheckpointFailureReason.CHECKPOINT_DECLINED_TASK_CLOSING));
				return false;
			}
		}

		long checkpointId = checkpointMetaData.getCheckpointId();
		long started = System.nanoTime();

		ChannelStateWriteResult channelStateWriteResult = checkpointOptions.isUnalignedCheckpoint() ?
								channelStateWriter.getAndRemoveWriteResult(checkpointId) :
								ChannelStateWriteResult.EMPTY;

		CheckpointStreamFactory storage = checkpointStorage.resolveCheckpointStorageLocation(checkpointId, checkpointOptions.getTargetLocation());

		try {
			for (StreamOperatorWrapper<?, ?> operatorWrapper : operatorChain.getAllOperators(true)) {
				if (!operatorWrapper.isClosed()) {
					operatorSnapshotsInProgress.put(
							operatorWrapper.getStreamOperator().getOperatorID(),
							buildOperatorSnapshotFutures(
									checkpointMetaData,
									checkpointOptions,
									operatorChain,
									operatorWrapper.getStreamOperator(),
									isCanceled,
									channelStateWriteResult,
									storage));
				}
			}
		} finally {
			checkpointStorage.clearCacheFor(checkpointId);
		}

		LOG.debug(
			"{} - finished synchronous part of checkpoint {}. Alignment duration: {} ms, snapshot duration {} ms",
			taskName,
			checkpointId,
			checkpointMetrics.getAlignmentDurationNanos() / 1_000_000,
			checkpointMetrics.getSyncDurationMillis());

		checkpointMetrics.setSyncDurationMillis((System.nanoTime() - started) / 1_000_000);
		return true;
	}

	private OperatorSnapshotFutures buildOperatorSnapshotFutures(
			CheckpointMetaData checkpointMetaData,
			CheckpointOptions checkpointOptions,
			OperatorChain<?, ?> operatorChain,
			StreamOperator<?> op,
			Supplier<Boolean> isCanceled,
			ChannelStateWriteResult channelStateWriteResult,
			CheckpointStreamFactory storage) throws Exception {
		OperatorSnapshotFutures snapshotInProgress = checkpointStreamOperator(
			op,
			checkpointMetaData,
			checkpointOptions,
			storage,
			isCanceled);
		if (op == operatorChain.getMainOperator()) {
			snapshotInProgress.setInputChannelStateFuture(
				channelStateWriteResult
					.getInputChannelStateHandles()
					.thenApply(StateObjectCollection::new)
					.thenApply(SnapshotResult::of));
		}
		if (op == operatorChain.getTailOperator()) {
			snapshotInProgress.setResultSubpartitionStateFuture(
				channelStateWriteResult
					.getResultSubpartitionStateHandles()
					.thenApply(StateObjectCollection::new)
					.thenApply(SnapshotResult::of));
		}
		return snapshotInProgress;
	}

	private Set<Long> createAbortedCheckpointSetWithLimitSize(int maxRecordAbortedCheckpoints) {
		return Collections.newSetFromMap(new LinkedHashMap<Long, Boolean>() {
			private static final long serialVersionUID = 1L;

			@Override
			protected boolean removeEldestEntry(Map.Entry<Long, Boolean> eldest) {
				return size() > maxRecordAbortedCheckpoints;
			}
		});
	}

	// Caches checkpoint output stream factories to prevent multiple output stream per checkpoint.
	// This could result from requesting output stream by different entities (this and channelStateWriter)
	// We can't just pass a stream to the channelStateWriter because it can receive checkpoint call earlier than this class
	// in some unaligned checkpoints scenarios
	private static class CachingCheckpointStorageWorkerView implements CheckpointStorageWorkerView {
		private final Map<Long, CheckpointStreamFactory> cache = new ConcurrentHashMap<>();
		private final CheckpointStorageWorkerView delegate;

		private CachingCheckpointStorageWorkerView(CheckpointStorageWorkerView delegate) {
			this.delegate = delegate;
		}

		void clearCacheFor(long checkpointId) {
			cache.remove(checkpointId);
		}

		@Override
		public CheckpointStreamFactory resolveCheckpointStorageLocation(long checkpointId, CheckpointStorageLocationReference reference) {
			return cache.computeIfAbsent(checkpointId, id -> {
				try {
					return delegate.resolveCheckpointStorageLocation(checkpointId, reference);
				} catch (IOException e) {
					throw new FlinkRuntimeException(e);
				}
			});
		}

		@Override
		public CheckpointStreamFactory.CheckpointStateOutputStream createTaskOwnedStateStream() throws IOException {
			return delegate.createTaskOwnedStateStream();
		}
	}

	private static OperatorSnapshotFutures checkpointStreamOperator(
			StreamOperator<?> op,
			CheckpointMetaData checkpointMetaData,
			CheckpointOptions checkpointOptions,
			CheckpointStreamFactory storageLocation,
			Supplier<Boolean> isCanceled) throws Exception {
		try {
			return op.snapshotState(
				checkpointMetaData.getCheckpointId(),
				checkpointMetaData.getTimestamp(),
				checkpointOptions,
				storageLocation);
		}
		catch (Exception ex) {
			if (!isCanceled.get()) {
				LOG.info(ex.getMessage(), ex);
			}
			throw ex;
		}
	}
}