I ended up figuring it out. Turns out a PHP script on the receiving
server was locking a session variable. Thanks so much for the response
and taking the time!

On 5/7/15, 1:15 AM, "Kamil Dudka" <kdudka_at_redhat.com> wrote:

>On Wednesday 06 May 2015 18:06:13 Stephen Hawkins wrote:
>> Hello,
>>
>> I am developing a Windows application that utilizes multiple threads to
>> upload chunks of data to a receiver. For this purpose we have utilized
>>the
>> easy interface since it was very easy to get started and works well with
>> the synchronous nature of what we are trying to accomplish with this.
>> Basically, we want each thread to read a chunk of data from disk,
>>upload it
>> to our ³receiver² (which is a Debian linux box with apache pre-fork)
>>which
>> does some integrity check stuff to verify that what we uploaded did
>>indeed
>> arrive in-tact, writes it to disk, and then sends a 200 back to our
>> application to notify it that the selected chunk we uploaded was
>>successful
>> and we can move onto the next one.
>>
>> The problem I am having is that when I run this application with
>>multiple
>> threads, my transfer speed grinds to a near halt, with sporadic bursts
>> being sent every 30 seconds. I can look at the logs on the receiver and
>> consistently see periods of inactivity that last for 30 seconds. Then I
>> see a burst of transfers, which quickly dies back down. The debugger
>>shows
>> that all of the threads are blocked on a call to select() inside of
>> curl_poll(). It seems like select() continuously returns 0, which
>>causes
>> curl_poll() to be called until select() finally does return something
>>other
>> than 0.
>
>If the threads are blocked on select(), it usually means that libcurl is
>waiting for data to be sent/received to/from the server. It looks to me
>like something hangs on your server when there are multiple connections
>being served at a time.
>
>Kamil

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Received on 2015-05-07