libcurl http post timeout - libcurl

Question

I am using curl version 7.15.5 in multi-thread environment. Each thread is initializing and freeing its own curl object. Below is the code, executed for each thread:
CURL* curl = curl_easy_init();
tRespBuffer respBuffer = {NULL, 0};
char errorBuf[CURL_ERROR_SIZE +1];
struct curl_slist *headers=NULL;
headers = curl_slist_append(headers, "Content-Type: text/xml; charset=gbk");
headers = curl_slist_append(headers, "Expect:");
curl_easy_setopt(curl, CURLOPT_URL, url_);
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
curl_easy_setopt(curl, CURLOPT_POSTFIELDS,encr.c_str());
curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE,strlen(encr.c_str()));
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, HttpSmsServer::processHttpResponse);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void*)&respBuffer);
curl_easy_setopt(curl, CURLOPT_TIMEOUT, 20); // wait for 20 seconds before aborting the transacttion
curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, errorBuf); // error returned if any..
curl_easy_setopt(curl, CURLOPT_NOSIGNAL, 1); // No signals allowed in case of multithreaded apps
res = curl_easy_perform(curl);
curl_slist_free_all(headers);
curl_easy_cleanup(curl);
All the four threads are posting data to http server simultaneously. I see HTTP response timeout for some of the POST requests (~3% of requests). Any idea what could be the reason of timeouts ? I assume http server should not take more than 20 seconds to respond back.

Answer 1

CURLOPT_TIMEOUT includes all the time of http request, have you transferred huge data?
CURLOPT_TIMEOUT：Pass a long as parameter containing the maximum time in seconds that you allow the libcurl transfer operation to take. Normally, name lookups can take a considerable time and limiting operations to less than a few minutes risk aborting perfectly normal operations.