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Subject [GitHub] ivmaykov commented on a change in pull request #753: ZOOKEEPER-3204: Reconfig tests are constantly failing on 3.5 after applying Java 11 fix
Date Wed, 06 Feb 2019 16:10:09 GMT
ivmaykov commented on a change in pull request #753: ZOOKEEPER-3204: Reconfig tests are constantly
failing on 3.5 after applying Java 11 fix
URL: https://github.com/apache/zookeeper/pull/753#discussion_r254336981
 
 

 ##########
 File path: zookeeper-server/src/main/java/org/apache/zookeeper/server/NettyServerCnxn.java
 ##########
 @@ -307,19 +281,126 @@ private boolean checkFourLetterWord(final Channel channel,
         }
     }
 
-    public void receiveMessage(ChannelBuffer message) {
+    /**
+     * Process incoming message. This should only be called from the event
+     * loop thread.
+     * @param buf the message bytes to process.
+     */
+    void processMessage(ByteBuf buf) {
+        assert channel.eventLoop().inEventLoop();
+        if (LOG.isDebugEnabled()) {
+            LOG.debug("0x{} queuedBuffer: {}",
+                    Long.toHexString(sessionId),
+                    queuedBuffer);
+        }
+
+        if (LOG.isTraceEnabled()) {
+            LOG.trace("0x{} buf {}",
+                    Long.toHexString(sessionId),
+                    ByteBufUtil.hexDump(buf));
+        }
+
+        if (throttled.get()) {
+            LOG.debug("Received message while throttled");
+            // we are throttled, so we need to queue
+            if (queuedBuffer == null) {
+                LOG.debug("allocating queue");
+                queuedBuffer = channel.alloc().buffer(buf.readableBytes());
+            }
+            queuedBuffer.writeBytes(buf);
+            if (LOG.isTraceEnabled()) {
+                LOG.trace("0x{} queuedBuffer {}",
+                        Long.toHexString(sessionId),
+                        ByteBufUtil.hexDump(queuedBuffer));
+            }
+        } else {
+            LOG.debug("not throttled");
+            if (queuedBuffer != null) {
+                queuedBuffer.writeBytes(buf);
+                processQueuedBuffer();
+            } else {
+                receiveMessage(buf);
+                // Have to check !closingChannel, because an error in
+                // receiveMessage() could have led to close() being called.
+                if (!closingChannel && buf.isReadable()) {
+                    if (LOG.isTraceEnabled()) {
+                        LOG.trace("Before copy {}", buf);
+                    }
+                    if (queuedBuffer == null) {
+                        queuedBuffer = channel.alloc().buffer(buf.readableBytes());
+                    }
+                    queuedBuffer.writeBytes(buf);
+                    if (LOG.isTraceEnabled()) {
+                        LOG.trace("Copy is {}", queuedBuffer);
+                        LOG.trace("0x{} queuedBuffer {}",
+                                Long.toHexString(sessionId),
+                                ByteBufUtil.hexDump(queuedBuffer));
+                    }
+                }
+            }
+        }
+    }
+
+    /**
+     * Try to process previously queued message. This should only be called
+     * from the event loop thread.
+     */
+    void processQueuedBuffer() {
+        assert channel.eventLoop().inEventLoop();
+        if (queuedBuffer != null) {
+            if (LOG.isTraceEnabled()) {
+                LOG.trace("processing queue 0x{} queuedBuffer {}",
+                        Long.toHexString(sessionId),
+                        ByteBufUtil.hexDump(queuedBuffer));
+            }
+            receiveMessage(queuedBuffer);
+            if (closingChannel) {
+                // close() could have been called if receiveMessage() failed
+                LOG.debug("Processed queue - channel closed, dropping remaining bytes");
+            } else if (!queuedBuffer.isReadable()) {
+                LOG.debug("Processed queue - no bytes remaining");
+                releaseQueuedBuffer();
+            } else {
+                LOG.debug("Processed queue - bytes remaining");
 
 Review comment:
   I don't think this will cause an OOM in most cases, as most client requests will not send
a lot of data, and once all of the incoming data is consumed the buffer will be freed. I guess
if there are many clients, and each is writing a lot of data to a znode, it could increase
memory usage. But I think the most data that can be stored in a znode is 1MB, so assuming
even 10k concurrent clients each writing 1MB that is 10GB of memory. It's a lot, but this
is a pretty extreme case and modern servers can easily have hundreds of GB.

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