What might be causing increasing latency?

["Trustin Lee (이희승)"]

Jannick Bitsch wrote:
> Hi
> 
> One possibility is that the effect is caused by
> http://en.wikipedia.org/wiki/Nagle's_algorithm. Could be that the tcp stack
> holds on  to the data with an increasing timeout algorithm, although that
> doesn't really account for the variance. You can try to turn it off.
> 
> From
> http://www.jboss.org/file-access/default/members/netty/freezone/api/3.2/index.html
> :
> ServerBootstrap b = ...;
> b.setOption("child.tcpNoDelay", true);
> 
> I actually think you need to set if to false to turn nagle's algorithm off,
> although that doesn't seem very intuitive :)

Actually, setting tcpNoDelay to true disables Nagle's algorithm.
Confusing! :)

> If that doesn't work, try to profile your gc and see if theres some
> excessive object allocations or something, that could cause it to introduce
> long pauses.
> 
> 
> Regards
> Jannick
> 
> 
> 2010/1/7 justkevin <filter.netty at wx3.com>
> 
>> After noticing my game app was occasionally running sluggish, I spent quite
>> a
>> bit of time trying to figure out why without success. If anyone has
>> suggestions on what to try I'd appreciate it. The details are long, but I
>> don't know what might be important:
>>
>> Details:
>>
>> The client is written in AS3.
>>
>> The server is written in Java using Netty 3.2 (I've updated to the most
>> recent alpha).
>>
>> I'm testing locally, with client and server on the same box.
>>
>> When the first client connects, latency as measured with a round-trip ping
>> pong is low, < 10 ms. It can remain low for a while, but eventually begins
>> increasing in spurts at varying rates.  For example, it might be < 10 ms
>> for
>> a while, then 50-100 ms for a while, then 100-200 ms, and so forth. There's
>> no upper limit, I've seen delays in multiple seconds. The larger the
>> latency, the larger the variance. The increases may be correlated to large
>> bursts of data.
>>
>> If I restart the client, the latency will usually drop, but not always.
>> Sometimes it restarts high.
>>
>> If I restart the server, the next client to connect will get a low latency.
>>
>> Using system times, I've established that the latency is entirely on the
>> downstream-- the ping takes 0ms to reach the server, and all the increase
>> is
>> between the time the pong is created and when its received by the client.
>> >From this I'm guessing it's something with how I'm sending messages.
>>
>> The only ChannelPipeline handler on outbound is a LengthFieldPrepender.
>>
>> Here is how I'm sending the message:
>>
>>                // A Netty channel expects a message in the format of a
>> ChannelBuffer:
>>                ChannelBuffer buffer = ChannelBuffers.dynamicBuffer();
>>                // Wrap the buffer with a ChannelBufferOutputStream, which
>> implements
>> DataOutput
>>                // (our messages expect to write to a DataOutput)
>>                ChannelBufferOutputStream output = new
>> ChannelBufferOutputStream(buffer);
>>                // First write the message id:
>>                output.writeByte(message.getId());
>>                // Then have the message write itself, checking to make sure
>> the message
>>                // obeys its length contract:
>>                int beforeLength = output.writtenBytes();
>>                int written = message.write(output);
>>                if(beforeLength + written != output.writtenBytes()){
>>                        logger.severe("Outbound message violated length
>> contract:" + message);
>>                        throw new RuntimeException("Message violated length
>> contract:" +
>> message);
>>                }
>>                // Finally, put into the channel. The channel pipeline
>> should already have
>> a length prepender:
>>                this.channel.write(buffer);
>>
>> Thanks in advance for any suggestions,
>> --
>> View this message in context:
>> http://n2.nabble.com/What-might-be-causing-increasing-latency-tp4269271p4269271.html
>> Sent from the Netty User Group mailing list archive at Nabble.com.
>> _______________________________________________
>> netty-users mailing list
>> netty-users at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/netty-users
>>
> 
> 
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-- 
what we call human nature in actuality is human habit
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