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Re: [libmicrohttpd] [EXTERNAL] Re: 0.9.71+ Connection Idle and Reuse Iss
Re: [libmicrohttpd] [EXTERNAL] Re: 0.9.71+ Connection Idle and Reuse Issue when Suspending and Resuming Connections
Thu, 7 Jan 2021 22:12:34 +0100
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On 1/7/21 9:58 PM, Earp, Damon N. (GSFC-619.0)[SCIENCE SYSTEMS AND
APPLICATIONS INC] via libmicrohttpd wrote:
> I've tested your version and indeed I see the expected behavior. I believe
> the disconnect is my lack of knowledge of the flow requirements of the access
> I was under the impression that in a non-100 continue requests queueing a
> response on the 2nd callback was fine, but I see from your changes I need to
> wait till the 3rd callback.
It is fine to do so on the 2nd, but there are two exceptions:
1) if there is upload_data -- then you have to wait until the upload is
done -- but that's not the case in your scenario; or
2) if you suspend during the 1st call, then that 1st call doesn't
count _because_ you suspended (so it never 'finished') ;-)
> Access handler flow from your updated main.c:
> Call 1. Increment the request access handler call count and return MHD_YES
> Call 2. Create the thread, suspend the request and return MHD_YES
> Call 3. queue the response return result
> It appears that I've been combining the first 2 calls incorrectly. I updated
> my main.c to do nothing on the first call, suspend and create thread on
> second call, and queue response on third and now am seeing the correct
>> The problem is that your logic queues a response during the *first*
>> callback to 'access_handler'
> Was that supposed to be *second* not *first*? I added extra logging and
> confirmed I am queuing on the second callback to the access_handler. As long
> as I moved the queuing of the response to the third call I saw proper reuse
> and idling of the connection.
> So to clarify:
> On all requests, regardless of method and existence of the Expect: 100
> header, queuing a response on the first or second call to the access handler
> is "early" and leads to a forced closing of the connection. Therefore on all
> non-"Expect: 100" requests, making the first call to the access handler a
> NOOP is a simple way to avoid queueing a response too early.
What is important is that you return MHD_YES once _without_ also
suspending. So if you didn't do that thread-activity, you could queue
the response on the 2nd call already.
> Thanks again for your time and help.
Sure. As I said, we know this part of the API can be a bit confusing and
needs improving ;-).
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