Adding/removing handles to the multi_handle produces unexpected result of curl_multi_perform

Hello!

I have a problem with adding/removing handlers with running multi_handler.
The use case is quite common: i need to make several requests and retry
then in case of failure. I'm using curl_multi to run those requests in
parallel and i remove handlers for the failed requests from the curl multi
handler and replace them with a new ones. It can be written in pseudocode
as:

auto multi_handle = curl_multi_init();
while(have_tasks){
  auto easy_handle = curl_easy_init();
  curl_multi_add_handle(multi_handle, easy_handle);
  curl_easy_setopt(m_handle, CURLOPT_URL, "http://www.example.org");
}
//Here goes the main loop
curl_multi_perform(multi_handle, &running_handles);
while(running_handles>0){
  curl_multi_wait(multi_handle)
  while(curl_multi_info_read(multi_handle) {
   if(CURLMSG_DONE) {
      //success
      curl_multi_remove_handle(multi_handle, easy_handle);
      curl_easy_cleanup(easy_handle);
   } else {
     //Failure, need to retry
      curl_multi_remove_handle(multi_handle, easy_handle);
      curl_easy_cleanup(easy_handle);
      auto easy_handle = curl_easy_init();
      curl_multi_add_handle(multi_handle, easy_handle);
      curl_easy_setopt(m_handle, CURLOPT_URL, "http://www.example.org");
  }
  curl_multi_perform(multi_handle, &running_handles);
 }

The full code (with stripped error handling and data handling) is published
at [1]

The problem is that when i have just a single request to process and that
request fails for some reason, so it's get recreated, the following
curl_multi_perform returns running_handlers equal to zero, despite that
fact, that i just added a new unprocessed handle, which is not what i
expect.

So, the question is - what i'm doing wrong and what is the correct way to
implement retries in that case, without recreating new multi handle?

[1] https://pastebin.com/Tk7LEe5f

-------------------------------------------------------------------
Unsubscribe: https://cool.haxx.se/list/listinfo/curl-library
Etiquette: https://curl.haxx.se/mail/etiquette.html
Received on 2019-09-27