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POHuge amount of packet drops and latency faced in netty
 

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  1. POHuge amount of packet drops and latency faced in netty
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    <p>I am using netty 3.5.11 with Jdk 1.7 on Ubuntu to receive a large amount of updates of stocks rates at a very high frequency. The message format being sent is JSON. The data is subscribed from topic on a redis server. There is a Subscriber for each symbol. The channel object is passed to multiple Subscribers and on receiving the data it is written to the client.</p> <p>Now the amount of data received is around 25,000 records in 2 minutes. Each record size is on an average around 500 bytes long.</p> <p>During test runs around 7500/8000 records were dropped because the channel was not writable. How do i avoid this. ?</p> <p>I also noticed that the latency increases systematically leading to updates being received after a long period. This happened when i I used Bufferedwritehandler to avoid packet drops.</p> <p>Here are the options that i set on bootstrap.</p> <pre><code>executionHandler = new ExecutionHandler( new OrderedMemoryAwareThreadPoolExecutor(Runtime.getRuntime().availableProcessors() * 2, 1000000, 10000000, 100, TimeUnit.MILLISECONDS)); serverBootStrap.setPipelineFactory(new ChannelPipelineFactory() { @Override public ChannelPipeline getPipeline() throws Exception { return Channels.pipeline(new PortUnificationServerHandler(getConfiguration(), executionHandler)); } }); serverBootStrap.setOption("child.tcpNoDelay", true); serverBootStrap.setOption("tcpNoDelay", true); serverBootStrap.setOption("child.keepAlive", true); serverBootStrap.setOption("child.reuseAddress", true); //setting buffer size can improve I/O serverBootStrap.setOption("child.sendBufferSize", 16777216); serverBootStrap.setOption("receiveBufferSize", 16777216);//1048576); // better to have an receive buffer predictor serverBootStrap.setOption("receiveBufferSizePredictorFactory", new AdaptiveReceiveBufferSizePredictorFactory(1024, 1024 * 16, 16777216));//1048576)); //if the server is sending 1000 messages per sec, optimum write buffer water marks will //prevent unnecessary throttling, Check NioSocketChannelConfig doc serverBootStrap.setOption("backlog", 1000); serverBootStrap.setOption("sendBufferSize", 16777216);//1048576); serverBootStrap.setOption("writeBufferLowWaterMark", 1024 * 1024 * 25); serverBootStrap.setOption("writeBufferHighWaterMark", 1024 * 1024 * 50); </code></pre> <p>The pipeline and handlers class</p> <pre><code>public class PortUnificationServerHandler extends FrameDecoder </code></pre> <p>{</p> <pre><code>private AppConfiguration appConfiguration; private final ExecutionHandler executionHandler; public PortUnificationServerHandler(AppConfiguration pAppConfiguration, ExecutionHandler pExecutionHandler) { appConfiguration = pAppConfiguration; this.executionHandler = pExecutionHandler; } @Override protected Object decode(ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer) throws Exception { String lRequest = buffer.toString(CharsetUtil.UTF_8); if (ConnectionServiceHelper.isValidJSON(lRequest)) { ObjectMapper lObjectMapper = new ObjectMapper(); StringReader lStringReader = new StringReader(lRequest); JsonNode lNode = lObjectMapper.readTree(lStringReader); if (lNode.get(Constants.REQUEST_TYPE).asText().trim().equalsIgnoreCase(Constants.LOGIN_REQUEST)) { JsonNode lDataNode1 = lNode.get(Constants.REQUEST_DATA); LoginRequest lLogin = lObjectMapper.treeToValue(lDataNode1, LoginRequest.class); if (lLogin.getCompress() != null) { if (lLogin.getCompress().trim().equalsIgnoreCase(Constants.COMPRESS_FLAG_TRUE)) { enableJSON(ctx); enableGzip(ctx); ctx.getPipeline().remove(this); } else { enableJSON(ctx); ctx.getPipeline().remove(this); } } else { enableJSON(ctx); ctx.getPipeline().remove(this); } } } // Forward the current read buffer as is to the new handlers. return buffer.readBytes(buffer.readableBytes()); } private void enableJSON(ChannelHandlerContext ctx) { ChannelPipeline pipeline = ctx.getPipeline(); boolean lHandlerExists = pipeline.getContext("bufferedwriter") != null; if (!lHandlerExists) { pipeline.addFirst("bufferedwriter", new MyBufferedWriteHandler()); // 80960 } boolean lHandlerExists = pipeline.getContext("framer") != null; if (!lHandlerExists) { pipeline.addLast("framer", new DelimiterBasedFrameDecoder(65535, new ChannelBuffer[] { ChannelBuffers.wrappedBuffer( new byte[] { '\n' }) })); } lHandlerExists = pipeline.getContext("decoder") != null; if (!lHandlerExists) { pipeline.addLast("decoder", new StringDecoder(CharsetUtil.UTF_8)); } lHandlerExists = pipeline.getContext("encoder") != null; if (!lHandlerExists) { pipeline.addLast("encoder", new StringEncoder(CharsetUtil.UTF_8)); } lHandlerExists = pipeline.getContext("executor") != null; if (!lHandlerExists) { pipeline.addLast("executor", executionHandler); } lHandlerExists = pipeline.getContext("handler") != null; if (!lHandlerExists) { pipeline.addLast("handler", new ConnectionServiceUpStreamHandler(appConfiguration)); } lHandlerExists = pipeline.getContext("unite") != null; if (!lHandlerExists) { pipeline.addLast("unite", new PortUnificationServerHandler(appConfiguration, executionHandler)); } } private void enableGzip(ChannelHandlerContext ctx) { ChannelPipeline pipeline = ctx.getPipeline(); //pipeline.remove("decoder"); //pipeline.addLast("decoder", new MyStringDecoder(CharsetUtil.UTF_8, true)); //pipeline.addLast("compress", new CompressionHandler(80, "gzipdeflater")); boolean lHandlerExists = pipeline.getContext("encoder") != null; if (lHandlerExists) { pipeline.remove("encoder"); } lHandlerExists = pipeline.getContext("gzipdeflater") != null; if (!lHandlerExists) { pipeline.addBefore("executor", "gzipdeflater", new ZlibEncoder(ZlibWrapper.GZIP)); } lHandlerExists = pipeline.getContext("lengthprepender") != null; if (!lHandlerExists) { pipeline.addAfter("gzipdeflater", "lengthprepender", new LengthFieldPrepender(4)); } } </code></pre> <p>}</p> <p>The BufferedWriterHandler</p> <pre><code> public class MyBufferedWriteHandler extends BufferedWriteHandler </code></pre> <p>{</p> <pre><code>private final AtomicLong bufferSize = new AtomicLong(); final Logger logger = LoggerFactory.getLogger(getClass()); public MyBufferedWriteHandler() { // Enable consolidation by default. super(true); } @Override public void writeRequested(ChannelHandlerContext ctx, MessageEvent e) throws Exception { ChannelBuffer data = (ChannelBuffer) e.getMessage(); if (e.getChannel().isWritable()) { long newBufferSize = bufferSize.get(); // Flush the queue if it gets larger than 8KiB. if (newBufferSize &gt; 0) { flush(); bufferSize.set(0); } ctx.sendDownstream(e); } else { logger.warn( "Buffering data for : " + e.getChannel().getRemoteAddress() ); super.writeRequested(ctx, e); bufferSize.addAndGet(data.readableBytes()); } } @Override public void channelInterestChanged(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception { if (e.getChannel().isWritable()) { flush(); } } </code></pre> <p>The function used in the Subscriber class to write data</p> <pre><code> public void writeToClient(Channel pClientChannel, String pMessage) throws IOException { String lMessage = pMessage; if (pClientChannel.isWritable()) { lMessage += Constants.RESPONSE_DELIMITER; pClientChannel.write(lMessage); } else { logger.warn(DroppedCounter++ + " droppped : " + pMessage); } } </code></pre> <p>I have implemented some of the suggestions that i read on stackoverflow and other sites. But i have not been successfull in resolving this issue.</p> <p>Kindly suggest or advice as to what am i missing ?</p> <p>Thanks</p>
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    1. USSunil Thamban
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