| Author |
Message |
< Yaws mailing list ~ Comet ("streaming HTTP/JS"), Yaws and hard-coded stream_time |
| Guest |
 Posted: Sun Feb 11, 2007 8:22 pm |
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Guest
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I'm experimenting with Yaws and the "Comet Pattern", which is about
sending real asynchronous stuff to the browser.
A browser portable way is i.e. having a hidden IFRAME which receives
MIME type text/html with content pieces of JS script tags which in
turn manipulate the main HTML DOM. Browsers will eval JS tags "as they
arrive" (incremental rendering).
see for example:
http://ajaxian.com/archives/iframe-script-tags-portable-comet
http://ajaxify.com/run/streaming/xmlHttpRequest/iframe/scriptTags/
and description of what I did below.
It's whats called "forever frame" in the following
http://alex.dojotoolkit.org/wp-content/LowLatencyData.pdf
versus the "long poll" technique.
--
Unfortunately, there seems to be a hard-coded timeout of 30s in
yaws_server.erl for streaming content.
I've attached a patch (for yaws_server.erl as it comes with Yaws 1.6
which allows
out/1
in Yaws to produce 2 new return values
{streamcontent_with_timeout, MimeType, FirstChunk, TimeOut}
{streamcontent_with_size_and_timeout, Sz, MimeType, FirstChunk, TimeOut}
which enables the user to set the timeout for streaming content,
including setting the TimeOut = infinity.
--
The patch seems to work, but I'm a total Erlang newbie .. so if someone
likes to use it, please QA it .. (in particular, I've not used/tested
the streamcontent_with_size_and_timeout stuff .. just extended it for
symmetry reasons).
Tobias
============
Details.
The content I produce in Yaws for the IFRAME contains only one
<erl></erl> piece which subscribes the Yaws worker process to a
registered (named) process P, and returns
{streamcontent, "text/html", "<html><body>"}.
Then, P will send JS script tags to all subscriber Yaws streaming
processes using
yaws_api:stream_chunk_deliver(..., "<script
type="text/javascript">window.parent.onData(5);</script>").
--
Problem is, when P does not send anything for some time, the Yaws
streaming worker dies with
=ERROR REPORT==== 11-Feb-2007::15:59:45 ===
Yaws process died: {stream_timeout,[{yaws_server,stream_loop_send,3},
{yaws_server,aloop,3},
{yaws_server,acceptor0,2},
{proc_lib,init_p,5}]}
--
I've looked for "stream_timeout", seems to be produced in fun
stream_loop_send(Priv, CliSock, FlushStatus) ->
TimeOut = case FlushStatus of
flushed -> 30000;
unflushed -> 300
end,
receive
...
of yaws_server.erl, which seems to hit the hardcoded timeout of 30s.
--
I've verified, that after hacking above line
"flushed -> 30000"
for
"flushed -> 120000"
and recompiling yaws_server.erl, both Firefox 2 and IE 7 will
not timeout by themselfes, but still receive asynchronous JS tags
via the IFRAME even after 110s inactivity.
--
With the attached patch, one is able to set the timeout
{streamcontent_with_timeout, "text/html", "<html><body>", infinity}.
from the .yaws page and both Firefox/IE will receive tags "forever".
I've tested IE7 for a waiting time of 15min between tags sent. No
problem, IE itself does not timeout.
--
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| rsaccon |
| Posted: Mon Feb 12, 2007 2:38 am |
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Joined: 09 Aug 2006
Posts: 144
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| I also experimented with comet pattern, and for iframe transport type, If I remember propperly, I sent after each 25 seconds a keep alive message to the browser, to prevent the 30 second timeout and to detect a disconnected browser, so |
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| noss |
| Posted: Mon Feb 12, 2007 9:28 am |
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User
Joined: 09 Oct 2005
Posts: 290
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Is the thirty second timeout documented? I recall finding out by
reading source code when my connections mysteriously died.
On 2/12/07, Tobias Oberstein <tobias.oberstein@gmx.de> wrote:
> > I set a timer to go off before thirty sec of inactivity. Then send a
> > 'noop' message.
>
> Well, ok. Thats a workaround.
>
> >
> > In my case that noop updated the ui to reflect chat inactivity rather
> > than silent failure. So it was not really a noop.
> >
>
> I can see that it might be useful to sent some heartbeat at least every
> 30-120s anyway in many scenarios.
>
> Also, I just checked Opera 9 .. and that beast _does_ timeout < 5min
> on IFRAMEs in contrast to IE 7 and Firefox 2 at least.
>
> Tobias
>
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| Guest |
| Posted: Tue Feb 13, 2007 9:18 pm |
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Guest
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> Is the thirty second timeout documented? I recall finding out by
> reading source code when my connections mysteriously died.
I saw the "stream_timeout" from the console when running Yaws
in interactive mode and grepped the sources ..
The yaws.pdf does not seem to mention it ..
Tobias
-------------------------------------------------------------------------
Using Tomcat but need to do more? Need to support web services, security?
Get stuff done quickly with pre-integrated technology to make your job easier.
Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642
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