[GitHub] rdhabalia commented on a change in pull request #620: added new entrypoint for reader to websocket proxy

[gi...@git.apache.org]

rdhabalia commented on a change in pull request #620: added new entrypoint for reader to websocket proxy
URL: https://github.com/apache/incubator-pulsar/pull/620#discussion_r133058980
 
 

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 File path: pulsar-websocket/src/main/java/org/apache/pulsar/websocket/ReaderHandler.java
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+/**
+ * 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.pulsar.websocket;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.time.ZoneId;
+import java.time.format.DateTimeFormatter;
+import java.util.Base64;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLongFieldUpdater;
+import java.util.concurrent.atomic.LongAdder;
+
+import javax.servlet.http.HttpServletRequest;
+
+import static org.apache.commons.lang3.StringUtils.isNotBlank;
+
+import org.apache.pulsar.client.api.ReaderConfiguration;
+import org.apache.pulsar.client.api.SubscriptionType;
+import org.apache.pulsar.client.impl.MessageIdImpl;
+import org.apache.pulsar.client.impl.ReaderImpl;
+import org.apache.pulsar.client.api.Consumer;
+import org.apache.pulsar.client.api.MessageId;
+import org.apache.pulsar.client.api.Reader;
+import org.apache.pulsar.common.naming.DestinationName;
+import org.apache.pulsar.common.util.ObjectMapperFactory;
+import org.apache.pulsar.websocket.data.ConsumerMessage;
+import org.eclipse.jetty.websocket.api.Session;
+import org.eclipse.jetty.websocket.api.WriteCallback;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.google.common.base.Splitter;
+
+/**
+ *
+ * WebSocket end-point url handler to handle incoming receive.
+ * <p>
+ * <b>receive:</b> socket-proxy keeps pushing messages to client by writing into session.<br/>
+ * </P>
+ *
+ */
+public class ReaderHandler extends AbstractWebSocketHandler {
+    private String subscription;
+    private final ReaderConfiguration conf;
+    private Reader reader;
+
+    private final int maxPendingMessages;
+    private final AtomicInteger pendingMessages = new AtomicInteger();
+    
+    private final LongAdder numMsgsDelivered;
+    private final LongAdder numBytesDelivered;
+    private volatile long msgDeliveredCounter = 0;
+    private static final AtomicLongFieldUpdater<ReaderHandler> MSG_DELIVERED_COUNTER_UPDATER =
+            AtomicLongFieldUpdater.newUpdater(ReaderHandler.class, "msgDeliveredCounter");
+
+    public ReaderHandler(WebSocketService service, HttpServletRequest request) {
+        super(service, request);
+        this.subscription = "";
+        this.conf = getReaderConfiguration();
+        this.maxPendingMessages = (conf.getReceiverQueueSize() == 0) ? 1 : conf.getReceiverQueueSize();
+        this.numMsgsDelivered = new LongAdder();
+        this.numBytesDelivered = new LongAdder();        
+    }
+
+    @Override
+    protected void createClient(Session session) {
+
+        try {
+            this.reader = service.getPulsarClient().createReader(topic, getMessageId(), conf);
+            this.subscription = ((ReaderImpl)this.reader).getConsumer().getSubscription(); 
+            this.service.addReader(this);
+            receiveMessage();
+        } catch (Exception e) {
+            log.warn("[{}] Failed in creating subscription {} on topic {}", session.getRemoteAddress(), subscription,
+                    topic, e);
+            close(WebSocketError.FailedToSubscribe, e.getMessage());
+        }
+    }
+
+	private void receiveMessage() {
+        if (log.isDebugEnabled()) {
+            log.debug("[{}] [{}] [{}] Receive next message", getSession().getRemoteAddress(), topic, subscription);
+        }
+
+        reader.readNextAsync().thenAccept(msg -> {
+            if (log.isDebugEnabled()) {
+                log.debug("[{}] [{}] [{}] Got message {}", getSession().getRemoteAddress(), topic, subscription,
+                        msg.getMessageId());
+            }
+
+            ConsumerMessage dm = new ConsumerMessage();
+            dm.messageId = Base64.getEncoder().encodeToString(msg.getMessageId().toByteArray());
+            dm.payload = Base64.getEncoder().encodeToString(msg.getData());
+            dm.properties = msg.getProperties();
+            dm.publishTime = DATE_FORMAT.format(Instant.ofEpochMilli(msg.getPublishTime()));
+            if (msg.hasKey()) {
+                dm.key = msg.getKey();
+            }
+            final long msgSize = msg.getData().length;
+
+            try {
+                getSession().getRemote()
+                        .sendString(ObjectMapperFactory.getThreadLocal().writeValueAsString(dm), new WriteCallback() {
+                            @Override
+                            public void writeFailed(Throwable th) {
+                                log.warn("[{}/{}] Failed to deliver msg to {} {}", reader.getTopic(), subscription,
+                                        getRemote().getInetSocketAddress().toString(), th.getMessage());
+                                pendingMessages.decrementAndGet();
+                                // schedule receive as one of the delivery failed
+                                service.getExecutor().execute(() -> receiveMessage());
+                            }
+
+                            @Override
+                            public void writeSuccess() {
+                                if (log.isDebugEnabled()) {
+                                    log.debug("[{}/{}] message is delivered successfully to {} ", reader.getTopic(),
+                                            subscription, getRemote().getInetSocketAddress().toString());
+                                }
+                                updateDeliverMsgStat(msgSize);
+                                pendingMessages.getAndDecrement();
+                            }
+                        });
+            } catch (JsonProcessingException e) {
+                close(WebSocketError.FailedToSerializeToJSON);
+            }
+
+            int pending = pendingMessages.incrementAndGet();
+            if (pending < maxPendingMessages) {
+                // Start next read in a separate thread to avoid recursion
+                service.getExecutor().execute(() -> receiveMessage());
+            } else {
+                // Resume delivery
+                receiveMessage();
 
 Review comment:
   Should't we stop delivery if `pending` reached to `maxPendingMessages` else it will keep sending messages to the client ? 
   Should we do the similar like [ConsumerHandler](https://github.com/apache/incubator-pulsar/blob/master/pulsar-websocket/src/main/java/org/apache/pulsar/websocket/ConsumerHandler.java#L166), after reaching `maxPendingMessages`, proxy-reader will send more message when it receives a new `readNext` request from client, same way consumer receives `ack-request`.? If that seems feasible solution then we can document the semantic into websocket-reader-doc as well.
   
   
   
 
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