Realtiming ajax?

[deostroll]

Suppose I have an asp page that has a response.write(something) in a
loop that would run for a considerable amount of time. Now, from my
client browser can I trap those server response messages (using ajax)
and print them on the browser?

(The thing is the asp page is still running over at the server...while
it is running I would want to monitor some variables that is part of
the program that is running over at the server)

--deostroll

 

[Anthony Jones]

To achieve what I think you are wanting , use response.flush to show

interim values while the asp page is running.
That'll send content to the client but the component on the client end needs
to be able to deliver that content via an event before the response is
complete.

The only component that can do that WinHTTP. I've never wired up it's
events in script to see if that can be done.

 

[keyser soze]

i think
you can use a session variable: session("progess")= 0
wich your "process.asp" can increase whenever you want
thus, you can retrieve it with ajax
invoking another page like "getprogress.asp"

 

[Anthony Jones]

i think
you can use a session variable: session("progess")= 0
wich your "process.asp" can increase whenever you want
thus, you can retrieve it with ajax
invoking another page like "getprogress.asp"

You can't use the session object in this way since it is single threaded.
You can't have a long running thread updating the session object and have
another thread read it. The request to getprogress.asp will queue until the
long running thread has completed.

It may be possible to use the application object or a DB to do the same
thing though.

 

[Anthony Jones]

You can't check the progress of an ASP script from the client side.

Not quite sure I understand you. Did you not suggest using Response.Flush
to send some content to the client before the ASP script is completed?

 

[keyser soze]

or writting/reading a file, i guess
named as [user_id].txt
(he will need to deal with the txt garbage, of course)

 

[deostroll]

Jon Paal said:

You can't check the progress of an ASP script from the client side.

I have tried using response.flush, it does not work.

Technically my requirement does not deal with checking the progress of
the asp script. Rather I want to monitor some variables at runtime.

--deostroll

 

[Anthony Jones]

Jon Paal said:


I have tried using response.flush, it does not work.

Technically my requirement does not deal with checking the progress of
the asp script. Rather I want to monitor some variables at runtime.

You need to turn off the standard ASP session management and turn off ASP
debugging before you can get ASP to process more than one request from the
same client.

 

[keyser soze]

wait,
please correct me if i don't got it:
are you saying that a page
with multiple ajax requests is not possible
to be processed in parallel,
with the standard session management ??

that is, i see that ajax is working on my page
but, behind the scenes, iis can process
only one request by session ???

all the work that i see ajax is doing
is not actually in paralell (with std session mgt) ??

 

[Anthony Jones]

wait,
please correct me if i don't got it:
are you saying that a page
with multiple ajax requests is not possible
to be processed in parallel,
with the standard session management ??

Yep. For each script to run in parrellel each needs to be executed in
different threads. Since the session object is only single thread it can
not be shared by two threads at the same time. Even if one of the scripts
has no need of the session object the ASP processor has no way to know that.
It has to make one of the ASP scripts wait until the first is finished so
that it can move the session object off one thread and give it to the other.

that is, i see that ajax is working on my page
but, behind the scenes, iis can process
only one request by session ???

ASP can only processs one request per session. Strictly speaking IIS
doesn't know what an ASP session is.

all the work that i see ajax is doing
is not actually in paralell (with std session mgt) ??

You've got it.

Note fetching other resources form IIS are unnaffected by this limitation.
You can have the download of two XML files in parrellel but that wouldn't
help with performance much. In fact in terms of perceived performance it
could do more harm than good.

Also note that by default IE only creates 2 outstanding connections to any
one server and FF allows 8.

 

[keyser soze]

it is the same on asp.net ?

Yep. For each script to run in parrellel each needs to be executed in
different threads. Since the session object is only single thread it can
not be shared by two threads at the same time. Even if one of the scripts
has no need of the session object the ASP processor has no way to know that.
It has to make one of the ASP scripts wait until the first is finished so
that it can move the session object off one thread and give it to the other.

ASP can only processs one request per session. Strictly speaking IIS
doesn't know what an ASP session is.


You've got it.

Note fetching other resources form IIS are unnaffected by this limitation.
You can have the download of two XML files in parrellel but that wouldn't
help with performance much. In fact in terms of perceived performance it
could do more harm than good.

Also note that by default IE only creates 2 outstanding connections to any
one server and FF allows 8.

 

[Anthony Jones]

it is the same on asp.net ?

I can't give you a definitive answer on that you perhaps need to as over in
microsoft.public.dotnet.framework.aspnet.

However since thread-safe session state containers aren't supported in
ASP.NET I suspect that ASP.NET has no choice but to serialise page access
per session

 

[khakman]

Check out these real-time ajax examples and the whitepaper that goes
with them...

http://ams.tibco.com

In these examples, multiple server-side data streams are multi-plexed
across a single persistent HTTP connection, then unpacked at the
client where they are published again to client-side ajax components.
The real-time data is served by a product from TIBCO called TIBCO Ajax
Message Service.

--Kevin Hakman (TIBCO).