Re: [staf-users] Async Remote Logging

[Yuesong W. <yue...@ya...>]

Thanks for the explaination. Things make more sense
now.

Yuesong

--- Charles Rankin <ra...@us...> wrote:
> 
> 
> 
> 
> sta...@li... said:
> 
> > Hi,
> > I want to write all my test logs to a central
> server.
> > To minimize the network delay I want to submit the
> log
> > request asynchronously. I wrote a test script that
> > submits mutiple asyn log requests to the remote
> server
> > in succession. The problem is they were not logged
> in
> > the order of the submission. I'm using a VB style
> > language that in turn uses the C api. Following is
> the
> > psuedo code:
> > For i = 1 To 100
> > submit2 _
> > ReqFireAndForget, _
> > "RemoteLogServer", _
> > "Log", _
> > "Log Global Logname MyLog Level Info Message " & i
> > Next i
> > I would expect the log message contains 1 to 100
> in
> > that order, but the acutal order seems random.
> > Am I doing something wrong? Is there a way to
> achieve
> > what I want to do?
> > Thanks,
> > Yuesong
> 
> STAF is a completely multi-threaded application. 
> Each incoming request is
> routed to a separate thread.  So, when using
> ReqFireAndForget, each request
> is in contention with every other request.  So,
> depending upon network
> latencies and even thread/process context switch
> timing, you can see out of
> order log entries as you are.
> 
> There is no easy fix for this inside STAFProc.  Even
> if STAFProc queued all
> incoming requests and dispersed them to threads,
> network latencies could
> still generate the behavior you are seeing.
> 
> There are a few ways around this for you.
> 
> 1) Simply do synchronous logging instead of the
> FireAndForget.  Depending
> on the amount of logging you are doing, you may not
> notice a difference.
> 
> 2) You could attach a sequence number (and/or a
> timestamp you generate) to
> all your log entries (probably at the beginning of
> the message).  Then when
> querying the log you can sort the messages by your
> sequence number.
> 
> 3) You could create a separate process/service to
> which you submit all your
> log requests.  This separate process/service would
> queue up your requests
> and then do synchronous log requests.
> 
> 4) If your program can be multi-threaded, then you
> can "post" your log
> messages to a queue on another thread, and have the
> other thread do
> synchronous logs.
> 
> It is certainly possible for us to modify the Log
> service (or create a new
> one) which would do something very similar to #3
> above.  Note, however,
> that it is still possible (in #3 above or with a
> change to the log service)
> for things to get out of order due to thread
> contention/scheduling,
> although this would be substantially less likely to
> happen.  We could
> probably also tweak the Log service to do a
> variation of #4, which should
> do sequential logging.
> 
> If you absolutely have to have things logged in a
> sequential fashion, then
> you will need to do #1, #2, or #4 above.
> 
> --
> Charles Rankin
> I do not speak for IBM
> 


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