thanks for the null expect tip, I'll try that; and yes, there is no
auth being used because this is a closed-circuit situation where PUT
was used because it is fast, reliable and convenient for frequent
small updates.

but this then raises a third question: If I did want to use auth, then
I would need to have the Expect: 100-continue header, right? and if
so, since this is always to a known client, would there be some way to
subvert the 1 second delay? Or would it be a non-issue because the
auth and no-continue would work just fine together?

On Sun, Sep 21, 2008 at 2:34 AM, Dan Fandrich <dan_at_coneharvesters.com> wrote:
> On Sun, Sep 21, 2008 at 12:19:13AM -0400, Gary Lawrence Murphy wrote:
>> I have two programs, one is a C-language program using libcurl (Linux)
>> to send a document to a perl-based receiver (also Linux), but the
>> conversation I see between the two machines is very strange:
>>
>> 1. 18:05:34.974033: receives "PUT / HTTP/1.1" header from libcurl PUT
>> server; the packet (in tcpdump) shows that it has Accept: */* and
>> Content-Length: 1095, then ends with "Expect: 100-continue"
>>
>> 2. 18:05:34.974049: client sends ACK
>>
>> 3. 18:05:34.976442: client sends an HTTP response which contains
>> "(HTTP/1.1 100 Continue"
>>
>> 4. 18:05:35.065209: client receives ACK from libcurl server
>>
>> 5. 18:05:36.065523: client receives the HTTP body from libcurl
>>
>> Forgive my noviceness, but there's two things I don't understand here,
>> and one of them is bogging down my transmissions:
>>
>> - Why doesn't the HTTP PUT message already contain the body? In the C
>
> This question has been hashed out many times before on this list (it
> should probably be added to the FAQ). The idea is to avoid sending a huge
> file only to have the server return a 401 Authorization Required or
> other error code and then have to send it all again. It's very rare
> for a server to allow an unauthenticated PUT, after all.
>
>> code I set up the curl call as one atomic item containing headers and
>> the body expecting this to be one transmission; why does the client
>> need to send an HTTP 100-continue response to the original request?
>> Is this discussed in RFC 2616? (I must have missed it) or is this
>> perhaps an ill-configured PUT request?
>>
>> - I can live with 100-Continue handshakes, but here is the really
>> bothersome part: Notice how the delay between the 100 Continue request
>> and the start of the response with the body is very nearly exactly one
>> second! I see this on every transfer. Why one second? that seems a
>> long time for a pause when the typical HTTP transmission is only a few
>> K in size. Again, is there perhaps some misconfig of the libcurl that
>> is causing this?
>
> The 1 second timeout is hard-coded in libcurl. Since HTTP 1.0 servers don't
> support 100-continue, this is a fallback mechanism that allows a transfer
> to continue anyway.
>
>> Here's the sequence of curl library calls:
>>
>> curl = curl_easy_init();
>> if (!curl) return NULL;
>>
>> curl_easy_setopt(curl, CURLOPT_DNS_CACHE_TIMEOUT, 150);
>> curl_easy_setopt(curl, CURLOPT_TIMEOUT, RESTIMEOUT);
>> curl_easy_setopt(curl, CURLOPT_MAXCONNECTS, 1);
>> curl_easy_setopt(curl, CURLOPT_FRESH_CONNECT, TRUE);
>>
>> curl_easy_setopt(curl, CURLOPT_READDATA, mem_buffer);
>> curl_easy_setopt(curl, CURLOPT_URL, target);
>> curl_easy_setopt(curl, CURLOPT_UPLOAD, TRUE) ;
>>
>> curl_easy_setopt(curl, CURLOPT_FORBID_REUSE, TRUE);
>> sprintf( string, "Content-Type: text/xml; charset=\"%s\"", charset);
>> slist = curl_slist_append(slist, string );
>> curl_easy_setopt(curl, CURLOPT_HTTPHEADER, slist);
>> curl_easy_setopt(curl, CURLOPT_INFILESIZE, file_size);
>> res = curl_easy_perform(curl);
>
> Interesting--no authentication options. I take it this isn't a publically-
> accessible server.
>
>> Why is curl_easy_perform(curl) introducing that one-second pause? Can
>> it be avoided?
>
> Sure it can--just set an empty Expect: header with CURLOPT_HTTPHEADER or
> set HTTP 1.0 mode with CURLOPT_HTTP_VERSION. The CVS version of curl will
> also automatically disable Expect: if it knows that the server only
> supports HTTP 1.0 (which isn't always possible to tell).
>
>>>> Dan
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Received on 2008-09-21