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From: Ward, David <>
Date: Mon, 27 Jan 2003 06:26:24 -0500

Thanks for the response, your original response was clear but it seemed to
contradict the official documentation as did my test.
I was confused as the man page indicates the timer value is the "maximum
time in seconds that you allow the libcurl transfer operation to take" and
therefore I assumed that the transfer was the request-response to the
ultimate destination and the entire transfer would use a single timer i.e.
not split the transfer into service components and that that one timer
operated using a signal. This assumption was incorrect.
From my tests it appears that the CURLOPT_TIMEOUT is safe to use in a
multi-threaded environment if you disable signals on your thread ... you
wont get the DNS timeout feature but you will recover if your destination
server hangs.

-----Original Message-----
From: Daniel Stenberg []
Sent: 27 January 2003 12:00
To: libcurl Mailing list

On Mon, 27 Jan 2003, Ward, David wrote:

> >Yes. The signal is used for stopping slow DNS name resolves, nothing
> >So, if you don't "hang" in the name resolve for very long, then it won't
> >abort with a signal but just a normal comparison and a return.

> Thanks for the response, but I'm still non the wiser. The DNS isnt
> as my http server is receiving the request and I'm forcing the http server
> to hang. My http server is just a simple socket that receives the http
> request but does not respond.

Right, then libcurl won't use a signal for the timeout.

> If I set the CURLOPT_TIMEOUT option my client times out after the
> time from its connection with the http server. I dont understand how this
> can happen as I've disabled the SIGALRM signal on my thread and apparently
> the timeout can only occur on reception of this signal.

Then pelase read the first paragraph of this mail one more time. I don't
how to put it in any other words: aborting the name resolve lookup is the
only thing that uses signals.

> I started testing this feature as I have a scenario with a hanging third
> party server and the timeout feature is just what I need. However as the
> documentation warns against using this timeout in a multi-threaded
> environment I want to find out why.

Because it uses a signal to cancel dns resolves.

> I think I can solve my problem by using the CURLOPT_LOW_SPEED_LIMIT
> as this doesnt come with a thread warning but I'm still curious as to how
> the CURLOPT_TIMEOUT really works!

Using a signal for the name resolve (until CURLOPT_NOSIGNAL was introduced
least), using regular comparisons for everything else. There's nothing

 Daniel Stenberg -- curl, cURL, Curl, CURL. Groks URLs.
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Received on 2003-01-27