DonalEvans commented on a change in pull request #6880:
URL: https://github.com/apache/geode/pull/6880#discussion_r718943694



##########
File path: 
geode-apis-compatible-with-redis/src/test/java/org/apache/geode/redis/internal/pubsub/PublisherTest.java
##########
@@ -0,0 +1,207 @@
+/*
+ * 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.geode.redis.internal.pubsub;
+
+import static org.apache.geode.redis.internal.netty.Coder.stringToBytes;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+import java.util.Collection;
+import java.util.List;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+import org.junit.Test;
+import org.mockito.ArgumentCaptor;
+
+import org.apache.geode.redis.internal.RegionProvider;
+import org.apache.geode.redis.internal.netty.Client;
+
+public class PublisherTest {
+  private final RegionProvider regionProvider = mock(RegionProvider.class);
+  private final Subscriptions subscriptions = mock(Subscriptions.class);
+  private final ExecutorService executorService = createExecutorService();
+  private final Publisher publisher = new Publisher(regionProvider, 
subscriptions, executorService);
+
+  private ExecutorService createExecutorService() {
+    // This service will do synchronous executioo

Review comment:
       Typo here, should be "execution"

##########
File path: 
geode-apis-compatible-with-redis/src/main/java/org/apache/geode/redis/internal/pubsub/Publisher.java
##########
@@ -0,0 +1,330 @@
+/*
+ * 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.geode.redis.internal.pubsub;
+
+import static 
org.apache.geode.logging.internal.executors.LoggingExecutors.newCachedThreadPool;
+import static org.apache.geode.redis.internal.netty.Coder.bytesToString;
+
+import java.io.DataInput;
+import java.io.DataOutput;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.TimeUnit;
+
+import org.apache.logging.log4j.Logger;
+
+import org.apache.geode.DataSerializer;
+import org.apache.geode.annotations.VisibleForTesting;
+import org.apache.geode.cache.execute.FunctionContext;
+import org.apache.geode.cache.execute.FunctionService;
+import org.apache.geode.cache.execute.ResultCollector;
+import org.apache.geode.distributed.DistributedMember;
+import org.apache.geode.internal.cache.execute.InternalFunction;
+import org.apache.geode.internal.serialization.DataSerializableFixedID;
+import org.apache.geode.internal.serialization.DeserializationContext;
+import org.apache.geode.internal.serialization.KnownVersion;
+import org.apache.geode.internal.serialization.SerializationContext;
+import org.apache.geode.logging.internal.log4j.api.LogService;
+import org.apache.geode.redis.internal.RegionProvider;
+import org.apache.geode.redis.internal.netty.Client;
+
+/**
+ * This class deals with doing a redis pubsub publish operation.
+ * Since publish requests from the same client must have order
+ * preserved, and since publish requests myst be done in a thread
+ * other than the one the request arrived from, this class has an
+ * instance of ClientPublisher for any Client that does a publish.
+ * The ClientPublisher maintains an ordered queue of requests
+ * and is careful to process them in the order they arrived.
+ * It supports batching them which can be a significant win as
+ * soon as a second geode server is added to the cluster.
+ * WARNING: The queue on the ClientPublisher is unbounded
+ * which can cause the server to run out of memory if the
+ * client keeps sending publish requests faster than the server
+ * can process them. It would be nice for this queue to have
+ * a bound but that could cause a hang because of the way
+ * we use Netty.
+ */
+public class Publisher {
+  private static final Logger logger = LogService.getLogger();
+
+  private final ExecutorService executor;
+  private final RegionProvider regionProvider;
+  private final Subscriptions subscriptions;
+  private final Map<Client, ClientPublisher> clientPublishers = new 
ConcurrentHashMap<>();
+
+  public Publisher(RegionProvider regionProvider, Subscriptions subscriptions) 
{
+    this.executor = createExecutorService();
+    this.regionProvider = regionProvider;
+    this.subscriptions = subscriptions;
+    registerPublishFunction();
+  }
+
+  @VisibleForTesting
+  Publisher(RegionProvider regionProvider, Subscriptions subscriptions, 
ExecutorService executor) {
+    this.executor = executor;
+    this.regionProvider = regionProvider;
+    this.subscriptions = subscriptions;
+    // no need to register function in unit tests
+  }
+
+  public void publish(Client client, byte[] channel, byte[] message) {
+    ClientPublisher clientPublisher =
+        clientPublishers.computeIfAbsent(client, key -> new ClientPublisher());
+    clientPublisher.publish(channel, message);
+  }
+
+  public void disconnect(Client client) {
+    clientPublishers.remove(client);
+  }
+
+  public void close() {
+    executor.shutdown();
+    try {
+      if (!executor.awaitTermination(1, TimeUnit.MINUTES)) {
+        logger.warn("Timed out waiting for queued publish requests to be 
sent.");
+      }
+    } catch (InterruptedException e) {
+      Thread.currentThread().interrupt();
+    }
+  }
+
+  @VisibleForTesting
+  int getClientCount() {
+    return clientPublishers.size();
+  }
+
+
+  private static ExecutorService createExecutorService() {
+    return newCachedThreadPool("GeodeRedisServer-Publish-", true);
+  }
+
+  private void registerPublishFunction() {
+    FunctionService.registerFunction(new PublishFunction(this));
+  }
+
+  @SuppressWarnings("unchecked")
+  private void internalPublish(List<PublishRequest> batch) {
+    Set<DistributedMember> remoteMembers = 
regionProvider.getRemoteRegionMembers();
+    try {
+      ResultCollector<?, ?> resultCollector = null;
+      try {
+        if (!remoteMembers.isEmpty()) {
+          // send function to remotes
+          resultCollector = FunctionService
+              .onMembers(remoteMembers)
+              .setArguments(batch)
+              .execute(PublishFunction.ID);
+        }
+      } finally {
+        // execute it locally
+        publishBatchToLocalSubscribers(batch);
+        if (resultCollector != null) {
+          // block until remote execute completes
+          resultCollector.getResult();
+        }
+      }
+    } catch (Exception e) {
+      // the onMembers contract is for execute to throw an exception
+      // if one of the members goes down.
+      if (logger.isDebugEnabled()) {
+        logger.debug(
+            "Exception executing publish function on batch {}. If a server 
departed during the publish then an exception is expected.",
+            batch, e);
+      }
+    }
+  }
+
+  private void publishBatchToLocalSubscribers(List<PublishRequest> batch) {
+    batch.forEach(request -> 
subscriptions.forEachSubscription(request.getChannel(),
+        (subscriptionName, channelToMatch, client, subscription) -> 
subscription.publishMessage(
+            channelToMatch != null, subscriptionName,
+            client, request.getChannel(), request.getMessage())));
+  }
+
+  public static class PublishRequest implements DataSerializableFixedID {
+    // note final can not be used because of DataSerializableFixedID
+    private byte[] channel;
+    private byte[] message;
+
+    public PublishRequest(byte[] channel, byte[] message) {
+      this.channel = channel;
+      this.message = message;
+    }
+
+    @SuppressWarnings("unused")
+    public PublishRequest() {
+      // needed for DataSerializableFixedID
+    }
+
+    public byte[] getChannel() {
+      return channel;
+    }
+
+    public byte[] getMessage() {
+      return message;
+    }
+
+    @Override
+    public int getDSFID() {
+      return PUBLISH_REQUEST;
+    }
+
+    @Override
+    public void toData(DataOutput out, SerializationContext context) throws 
IOException {
+      DataSerializer.writeByteArray(getChannel(), out);
+      DataSerializer.writeByteArray(getMessage(), out);
+    }
+
+    @Override
+    public void fromData(DataInput in, DeserializationContext context)
+        throws IOException, ClassNotFoundException {
+      channel = DataSerializer.readByteArray(in);
+      message = DataSerializer.readByteArray(in);
+    }
+
+    @Override
+    public KnownVersion[] getSerializationVersions() {
+      return null;
+    }
+
+    @Override
+    public String toString() {
+      return "PublishRequest{" +
+          "channel=" + bytesToString(channel) +
+          ", message=" + bytesToString(message) +
+          '}';
+    }
+  }
+
+  /**
+   * Manages all the publish requests from a particular client.
+   * The order of these requests is maintained, and they will be
+   * delivered to subscribers in that order.
+   * Since the delivery to subscribers can be slower than the rate
+   * at which publish requests arrive, this publisher supports
+   * batching so allow multiple requests to be sent with a single
+   * function call.
+   */
+  private class ClientPublisher {
+    /**
+     * The queue of incoming publish requests from a particular client.
+     */
+    private final BlockingQueue<PublishRequest> requests = new 
LinkedBlockingQueue<>();
+    private static final int MAX_BATCH_SIZE = 256;
+    /**
+     * Requests are removed from the "requests" queue and put into this batch.
+     * The batch will contain up to MAX_BATCH_SIZE requests but could contain
+     * any number less than that. All the requests added to this batch will be
+     * sent to subscribers before an attempt is made to fill it again.
+     */
+    private final List<PublishRequest> batch = new ArrayList<>(MAX_BATCH_SIZE);
+    /**
+     * True if an executor thread is currently working on our queue.
+     * Any use of this field must be protected by synchronization.
+     * Note that currently only a single executor thread will be working on
+     * a given ClientPublisher.
+     */
+    private boolean active;
+
+    public void publish(byte[] channel, byte[] message) {
+      // Only one thread for a given Client will call this method
+      // and this is the only place that adds to the queue.
+      // But one of the executor threads can be concurrently
+      // removing items from the queue.
+      requests.add(new PublishRequest(channel, message));
+      fillBatchIfNeeded();
+    }
+
+    private synchronized void fillBatchIfNeeded() {
+      // if active then the executor is already working on our batch
+      if (!active) {
+        // This should only happen when our queue is empty,
+        // and we add a request to it.
+        fillBatch();
+      }
+    }
+
+    private synchronized void fillBatch() {
+      batch.clear();
+      if (requests.drainTo(batch, MAX_BATCH_SIZE) > 0) {
+        active = true;
+        publishBatch();
+      } else {
+        active = false;
+      }
+    }
+
+    private void publishBatch() {
+      executor.execute(() -> {
+        try {
+          internalPublish(batch);
+        } finally {
+          fillBatch();

Review comment:
       In situations with high publish throughput from one client, is it 
possible that these recursive calls to `fillBatch()` might cause a stack 
overflow?

##########
File path: 
geode-apis-compatible-with-redis/src/main/java/org/apache/geode/redis/internal/pubsub/Publisher.java
##########
@@ -0,0 +1,330 @@
+/*
+ * 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.geode.redis.internal.pubsub;
+
+import static 
org.apache.geode.logging.internal.executors.LoggingExecutors.newCachedThreadPool;
+import static org.apache.geode.redis.internal.netty.Coder.bytesToString;
+
+import java.io.DataInput;
+import java.io.DataOutput;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.TimeUnit;
+
+import org.apache.logging.log4j.Logger;
+
+import org.apache.geode.DataSerializer;
+import org.apache.geode.annotations.VisibleForTesting;
+import org.apache.geode.cache.execute.FunctionContext;
+import org.apache.geode.cache.execute.FunctionService;
+import org.apache.geode.cache.execute.ResultCollector;
+import org.apache.geode.distributed.DistributedMember;
+import org.apache.geode.internal.cache.execute.InternalFunction;
+import org.apache.geode.internal.serialization.DataSerializableFixedID;
+import org.apache.geode.internal.serialization.DeserializationContext;
+import org.apache.geode.internal.serialization.KnownVersion;
+import org.apache.geode.internal.serialization.SerializationContext;
+import org.apache.geode.logging.internal.log4j.api.LogService;
+import org.apache.geode.redis.internal.RegionProvider;
+import org.apache.geode.redis.internal.netty.Client;
+
+/**
+ * This class deals with doing a redis pubsub publish operation.
+ * Since publish requests from the same client must have order
+ * preserved, and since publish requests myst be done in a thread
+ * other than the one the request arrived from, this class has an
+ * instance of ClientPublisher for any Client that does a publish.
+ * The ClientPublisher maintains an ordered queue of requests
+ * and is careful to process them in the order they arrived.
+ * It supports batching them which can be a significant win as
+ * soon as a second geode server is added to the cluster.
+ * WARNING: The queue on the ClientPublisher is unbounded
+ * which can cause the server to run out of memory if the
+ * client keeps sending publish requests faster than the server
+ * can process them. It would be nice for this queue to have
+ * a bound but that could cause a hang because of the way
+ * we use Netty.
+ */
+public class Publisher {
+  private static final Logger logger = LogService.getLogger();
+
+  private final ExecutorService executor;
+  private final RegionProvider regionProvider;
+  private final Subscriptions subscriptions;
+  private final Map<Client, ClientPublisher> clientPublishers = new 
ConcurrentHashMap<>();
+
+  public Publisher(RegionProvider regionProvider, Subscriptions subscriptions) 
{
+    this.executor = createExecutorService();
+    this.regionProvider = regionProvider;
+    this.subscriptions = subscriptions;
+    registerPublishFunction();
+  }
+
+  @VisibleForTesting
+  Publisher(RegionProvider regionProvider, Subscriptions subscriptions, 
ExecutorService executor) {
+    this.executor = executor;
+    this.regionProvider = regionProvider;
+    this.subscriptions = subscriptions;
+    // no need to register function in unit tests
+  }
+
+  public void publish(Client client, byte[] channel, byte[] message) {
+    ClientPublisher clientPublisher =
+        clientPublishers.computeIfAbsent(client, key -> new ClientPublisher());
+    clientPublisher.publish(channel, message);
+  }
+
+  public void disconnect(Client client) {
+    clientPublishers.remove(client);
+  }
+
+  public void close() {
+    executor.shutdown();
+    try {
+      if (!executor.awaitTermination(1, TimeUnit.MINUTES)) {
+        logger.warn("Timed out waiting for queued publish requests to be 
sent.");
+      }
+    } catch (InterruptedException e) {
+      Thread.currentThread().interrupt();
+    }
+  }
+
+  @VisibleForTesting
+  int getClientCount() {
+    return clientPublishers.size();
+  }
+
+
+  private static ExecutorService createExecutorService() {
+    return newCachedThreadPool("GeodeRedisServer-Publish-", true);
+  }
+
+  private void registerPublishFunction() {
+    FunctionService.registerFunction(new PublishFunction(this));
+  }
+
+  @SuppressWarnings("unchecked")
+  private void internalPublish(List<PublishRequest> batch) {
+    Set<DistributedMember> remoteMembers = 
regionProvider.getRemoteRegionMembers();
+    try {
+      ResultCollector<?, ?> resultCollector = null;
+      try {
+        if (!remoteMembers.isEmpty()) {
+          // send function to remotes
+          resultCollector = FunctionService
+              .onMembers(remoteMembers)
+              .setArguments(batch)
+              .execute(PublishFunction.ID);
+        }
+      } finally {
+        // execute it locally
+        publishBatchToLocalSubscribers(batch);
+        if (resultCollector != null) {
+          // block until remote execute completes
+          resultCollector.getResult();
+        }
+      }
+    } catch (Exception e) {
+      // the onMembers contract is for execute to throw an exception
+      // if one of the members goes down.
+      if (logger.isDebugEnabled()) {
+        logger.debug(
+            "Exception executing publish function on batch {}. If a server 
departed during the publish then an exception is expected.",
+            batch, e);
+      }
+    }
+  }
+
+  private void publishBatchToLocalSubscribers(List<PublishRequest> batch) {
+    batch.forEach(request -> 
subscriptions.forEachSubscription(request.getChannel(),
+        (subscriptionName, channelToMatch, client, subscription) -> 
subscription.publishMessage(
+            channelToMatch != null, subscriptionName,
+            client, request.getChannel(), request.getMessage())));
+  }
+
+  public static class PublishRequest implements DataSerializableFixedID {
+    // note final can not be used because of DataSerializableFixedID
+    private byte[] channel;
+    private byte[] message;
+
+    public PublishRequest(byte[] channel, byte[] message) {
+      this.channel = channel;
+      this.message = message;
+    }
+
+    @SuppressWarnings("unused")
+    public PublishRequest() {
+      // needed for DataSerializableFixedID
+    }
+
+    public byte[] getChannel() {
+      return channel;
+    }
+
+    public byte[] getMessage() {
+      return message;
+    }
+
+    @Override
+    public int getDSFID() {
+      return PUBLISH_REQUEST;
+    }
+
+    @Override
+    public void toData(DataOutput out, SerializationContext context) throws 
IOException {
+      DataSerializer.writeByteArray(getChannel(), out);
+      DataSerializer.writeByteArray(getMessage(), out);
+    }
+
+    @Override
+    public void fromData(DataInput in, DeserializationContext context)
+        throws IOException, ClassNotFoundException {
+      channel = DataSerializer.readByteArray(in);
+      message = DataSerializer.readByteArray(in);
+    }
+
+    @Override
+    public KnownVersion[] getSerializationVersions() {
+      return null;
+    }
+
+    @Override
+    public String toString() {
+      return "PublishRequest{" +
+          "channel=" + bytesToString(channel) +
+          ", message=" + bytesToString(message) +
+          '}';
+    }
+  }
+
+  /**
+   * Manages all the publish requests from a particular client.
+   * The order of these requests is maintained, and they will be
+   * delivered to subscribers in that order.
+   * Since the delivery to subscribers can be slower than the rate
+   * at which publish requests arrive, this publisher supports
+   * batching so allow multiple requests to be sent with a single

Review comment:
       Typo here, I think, should "so allow" be "to allow"?

##########
File path: 
geode-apis-compatible-with-redis/src/main/java/org/apache/geode/redis/internal/pubsub/Publisher.java
##########
@@ -0,0 +1,330 @@
+/*
+ * 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.geode.redis.internal.pubsub;
+
+import static 
org.apache.geode.logging.internal.executors.LoggingExecutors.newCachedThreadPool;
+import static org.apache.geode.redis.internal.netty.Coder.bytesToString;
+
+import java.io.DataInput;
+import java.io.DataOutput;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.TimeUnit;
+
+import org.apache.logging.log4j.Logger;
+
+import org.apache.geode.DataSerializer;
+import org.apache.geode.annotations.VisibleForTesting;
+import org.apache.geode.cache.execute.FunctionContext;
+import org.apache.geode.cache.execute.FunctionService;
+import org.apache.geode.cache.execute.ResultCollector;
+import org.apache.geode.distributed.DistributedMember;
+import org.apache.geode.internal.cache.execute.InternalFunction;
+import org.apache.geode.internal.serialization.DataSerializableFixedID;
+import org.apache.geode.internal.serialization.DeserializationContext;
+import org.apache.geode.internal.serialization.KnownVersion;
+import org.apache.geode.internal.serialization.SerializationContext;
+import org.apache.geode.logging.internal.log4j.api.LogService;
+import org.apache.geode.redis.internal.RegionProvider;
+import org.apache.geode.redis.internal.netty.Client;
+
+/**
+ * This class deals with doing a redis pubsub publish operation.
+ * Since publish requests from the same client must have order
+ * preserved, and since publish requests myst be done in a thread
+ * other than the one the request arrived from, this class has an
+ * instance of ClientPublisher for any Client that does a publish.
+ * The ClientPublisher maintains an ordered queue of requests
+ * and is careful to process them in the order they arrived.
+ * It supports batching them which can be a significant win as
+ * soon as a second geode server is added to the cluster.
+ * WARNING: The queue on the ClientPublisher is unbounded
+ * which can cause the server to run out of memory if the
+ * client keeps sending publish requests faster than the server
+ * can process them. It would be nice for this queue to have
+ * a bound but that could cause a hang because of the way
+ * we use Netty.
+ */
+public class Publisher {
+  private static final Logger logger = LogService.getLogger();
+
+  private final ExecutorService executor;
+  private final RegionProvider regionProvider;
+  private final Subscriptions subscriptions;
+  private final Map<Client, ClientPublisher> clientPublishers = new 
ConcurrentHashMap<>();
+
+  public Publisher(RegionProvider regionProvider, Subscriptions subscriptions) 
{
+    this.executor = createExecutorService();
+    this.regionProvider = regionProvider;
+    this.subscriptions = subscriptions;
+    registerPublishFunction();
+  }
+
+  @VisibleForTesting
+  Publisher(RegionProvider regionProvider, Subscriptions subscriptions, 
ExecutorService executor) {
+    this.executor = executor;
+    this.regionProvider = regionProvider;
+    this.subscriptions = subscriptions;
+    // no need to register function in unit tests
+  }
+
+  public void publish(Client client, byte[] channel, byte[] message) {
+    ClientPublisher clientPublisher =
+        clientPublishers.computeIfAbsent(client, key -> new ClientPublisher());
+    clientPublisher.publish(channel, message);
+  }
+
+  public void disconnect(Client client) {
+    clientPublishers.remove(client);
+  }
+
+  public void close() {
+    executor.shutdown();
+    try {
+      if (!executor.awaitTermination(1, TimeUnit.MINUTES)) {
+        logger.warn("Timed out waiting for queued publish requests to be 
sent.");
+      }
+    } catch (InterruptedException e) {
+      Thread.currentThread().interrupt();
+    }
+  }
+
+  @VisibleForTesting
+  int getClientCount() {
+    return clientPublishers.size();
+  }
+
+
+  private static ExecutorService createExecutorService() {
+    return newCachedThreadPool("GeodeRedisServer-Publish-", true);
+  }
+
+  private void registerPublishFunction() {
+    FunctionService.registerFunction(new PublishFunction(this));
+  }
+
+  @SuppressWarnings("unchecked")
+  private void internalPublish(List<PublishRequest> batch) {
+    Set<DistributedMember> remoteMembers = 
regionProvider.getRemoteRegionMembers();
+    try {
+      ResultCollector<?, ?> resultCollector = null;
+      try {
+        if (!remoteMembers.isEmpty()) {
+          // send function to remotes
+          resultCollector = FunctionService
+              .onMembers(remoteMembers)
+              .setArguments(batch)
+              .execute(PublishFunction.ID);
+        }
+      } finally {
+        // execute it locally
+        publishBatchToLocalSubscribers(batch);
+        if (resultCollector != null) {
+          // block until remote execute completes
+          resultCollector.getResult();
+        }
+      }
+    } catch (Exception e) {
+      // the onMembers contract is for execute to throw an exception
+      // if one of the members goes down.
+      if (logger.isDebugEnabled()) {
+        logger.debug(
+            "Exception executing publish function on batch {}. If a server 
departed during the publish then an exception is expected.",
+            batch, e);
+      }
+    }
+  }
+
+  private void publishBatchToLocalSubscribers(List<PublishRequest> batch) {
+    batch.forEach(request -> 
subscriptions.forEachSubscription(request.getChannel(),
+        (subscriptionName, channelToMatch, client, subscription) -> 
subscription.publishMessage(
+            channelToMatch != null, subscriptionName,
+            client, request.getChannel(), request.getMessage())));
+  }
+
+  public static class PublishRequest implements DataSerializableFixedID {
+    // note final can not be used because of DataSerializableFixedID
+    private byte[] channel;
+    private byte[] message;
+
+    public PublishRequest(byte[] channel, byte[] message) {
+      this.channel = channel;
+      this.message = message;
+    }
+
+    @SuppressWarnings("unused")
+    public PublishRequest() {
+      // needed for DataSerializableFixedID
+    }
+
+    public byte[] getChannel() {
+      return channel;
+    }
+
+    public byte[] getMessage() {
+      return message;
+    }
+
+    @Override
+    public int getDSFID() {
+      return PUBLISH_REQUEST;
+    }
+
+    @Override
+    public void toData(DataOutput out, SerializationContext context) throws 
IOException {
+      DataSerializer.writeByteArray(getChannel(), out);
+      DataSerializer.writeByteArray(getMessage(), out);
+    }
+
+    @Override
+    public void fromData(DataInput in, DeserializationContext context)
+        throws IOException, ClassNotFoundException {

Review comment:
       `ClassNotFoundException` is never thrown from this method.




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