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From Rob Davies <rajdav...@gmail.com>
Subject Re: High latency for small messages problem
Date Fri, 02 Feb 2007 10:49:32 GMT
this is odd!

ActiveMQ writes messages onto the transport (in this case a tcp/ip  
socket) asap. As nagles has no affect, I suspect this is an OS issue

cheers,

Rob Davies
http://rajdavies.blogspot.com/



On 2 Feb 2007, at 09:33, davidmc wrote:

>
> Hello,
>
> We are evaluating the possible use of ActiveMQ in our projects and  
> have
> encountered this problem.
>
> When sending small messages (for example, ByteMessages with a 1KB byte
> array) from a producer to a consumer through a broker, there is  
> much higher
> latency than with bigger messages (for example, ByteMessages with a  
> 32KB
> byte array), using the TCP transport.
> Changing the socketBufferSize parameter, the tcpNoDelayEnabled flag  
> does not
> help.
> Version of ActiveMQ is 4.1, and in 4.0 there is also this problem.
>
> Our test is as follows: one JVM is the broker, the other JVM runs a  
> producer
> and a consumer in separate threads (with separate connections and  
> sessions).
> We are using a queue, no persistence, no transactions,
> Session.AUTO_ACKNOWLEDGE.
> The producer sends a message just after taking note of the time with
> System.nanoTime(), and then waits on a semaphore.
> When the consumer receives the message (implementing the onMessage 
> () method
> of the MessageListener interface), the first thing that is done is  
> taking
> notice of the time with System.nanoTime().  The difference in time is
> computed and written to a file, after which the consumer releases the
> semaphore so that the producer sends the next message.
>
> With 1 machine running Red Hat EL4 Update 3, hosting both the  
> broker process
> and the producer/consumer process, we get a latency of 39ms with 1KB
> ByteMessages and latency of 0-1ms with 32KB ByteMessages. The  
> frontier for
> latency appearing seems to be around 16KB.
> With 1 machine running WinXP Pro SP2, hosting both the broker  
> process and
> the producer/consumer process, we get no latency (0-1 ms) with  
> messages of
> any size between 1KB and 32KB.
> With 2 machines in a LAN, no matter the combination of WinXP /  
> Linux (even 2
> WinXP machines) we get high latency (even 200 ms for 2 WinXP  
> machines) with
> 1KB messages and much lower latency (not 0, but low) with 32 KB  
> messages.
>
> Some more facts:
> The first 1KB message has high latency (as expected due to  
> initialization of
> stuff), the next 8-20 have no latency, and then the rest have high  
> latency.
> In Linux localhost case, if the producer waits 1 second between  
> sending 1KB
> messages, latency is low. Have not tried in other scenarios.
> Normally we do tests restarting the broker each time. But, if we do  
> not
> restart the broker, the results can be more strange. Sometimes,  
> there is a
> pattern where a 1KB message has no latency, the next had 39ms  
> latency, the
> next has no latency, the next has 39ms latency, etc. In one of  
> these times
> we took an Ethereal trace and found that the producer was sending 2  
> messages
> in the same TCP packet of around 2KB size.
>
> The broker configuration file is:
> http://www.nabble.com/file/6205/activemq.xml activemq.xml
>
> The code to perform the test is:
> http://www.nabble.com/file/6207/LatencyTest.java LatencyTest.java
>
> Here are some logs we have taken:
> http://www.nabble.com/file/6206/logs.zip logs.zip
> For 1KB messages you also have ethereal logs (32KB message ethereal  
> logs are
> too big files).
> In every case, the file "client.txt" is the log of the producer/ 
> consumer
> process, the file "broker.txt" is the log of the broker process.  
> Both these
> logs use the log4j logger of ActiveMQ.
> The "nolog" folders have logs without use of the log4j logger, since
> printing lots of messages disturbs a bit the results.
> Then you have a file called for example 1BytesMessage.txt (stands  
> for 1KB
> messages), with the latency times and time of receiving by the  
> consumer.
>
> All this is very strange... we do not know if the problem lies in  
> the Linux
> TCP stack, the Java I/O or networking libraries, ActiveMQ code,  
> some lack of
> proper configuration... we believe however that it is the producer  
> which is
> holding sometimes a message before sending the packet to the broker.
> -- 
> View this message in context: http://www.nabble.com/High-latency- 
> for-small-messages-problem-tf3159901.html#a8764113
> Sent from the ActiveMQ - User mailing list archive at Nabble.com.
>








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