What might be causing increasing latency?

[Jannick Bitsch]

Hehe, that sounds like the logical value. My first search for 'netty
tcpnodelay" returned this
http://www.jboss.org/file-access/default/members/jbossmessaging/freezone/docs/usermanual-2.0.0.beta1/html/configuring-transports.html
which states "jbm.remoting.netty.tcpnodelay. If this is true then Nagle's
algorithm <http://en.wikipedia.org/wiki/Nagle's_algorithm> will be enabled.
The default value for this property is true."

Clearly not easy to get right :)


- Jannick


2010/1/8 "Trustin Lee (이희승)" <trustin at gmail.com>

> 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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> >
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> --
> what we call human nature in actuality is human habit
> http://gleamynode.net/
>
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