> Am 31.05.2024 um 06:30 schrieb Cao Duc Quan via curl-library
> <curl-library@lists.haxx.se>:
>
> Hi,
>
> Here is the main flow in my application with CURLM
>
> struct Request {
> CURL *easy;
> // other data
> }
>
> int on_close_socket(void* clientp, curl_socket_t sock) {
> struct Request *request = (struct Request*)clientp;
> // log some metrics for request
> close(sock);
> return 0;
> }
>
> struct Request* alloc_request(const char* url) {
> struct Request* request = malloc(sizeof(struct Request));
>
> request->easy = curl_easy_init();
> curl_easy_setopt(curl, CURLOPT_CLOSESOCKETFUNCTION, on_close_socket);
> curl_easy_setopt(curl, CURLOPT_CLOSESOCKETDATA, request);
> // other init
> }
>
> void close_request(struct Request* request) {
> curl_easy_cleanup(request->easy);
> free(request);
> }
>
> struct Request* lkup_request(CURL *easy) {
> // lookup request from easy in active queue
> }
>
> void cleanup_finished_request(CURLM *multi) {
> struct CURLMsg *m;
> do {
> int msgq = 0;
> m = curl_multi_info_read(multi, &msgq);
> if(m && (m->msg == CURLMSG_DONE)) {
> CURL *e = m->easy_handle;
> curl_multi_remove_handle(multi, e);
> struct Request* request = lkup_request(e);
> close_request(request);
> }
> } while(m);
> }
>
> void deque_next_request(CURLM *multi) {
> // get url request and construct
> struct Request* request = alloc_request(url);
>
> curl_multi_add_handle(multi, request->easy);
> // add request to active queue
> }
>
> void thread_loop() {
> CURLM *multi = curl_multi_init();
> int still_running = 1;
>
> while(still_running) {
> deque_next_request();
> CURLMcode mc = curl_multi_perform(multi, &still_running);
>
> cleanup_finished_request();
> if(!mc && still_running)
>
> /* wait for activity, timeout or "nothing" */
> mc = curl_multi_poll(multi, NULL, 0, 1000, NULL);
>
> if(mc) {
> fprintf(stderr, "curl_multi_poll() failed, code %d.\n", (int)mc);
> break;
> }
> }
> }
>
> In alloc_request() create a request object which includes an easy handler and
> hold private data and install CURLOPT_CLOSESOCKETFUNCTION and
> CURLOPT_CLOSESOCKETDATA. The problem is that when the request is finished
> before the socket closes, the CLOSESOCKEDATA becomes invalid since it binds
> to the request object which will be free when the request finishes.
>
> I did some checks and the curl_easy_cleanup() did not reset the socket
> callback. It seems to me the close socket callback and its data only set once
> in allocate_conn() function in lib/url.c and won't be updated even if we
> recall this
> curl_easy_setopt(curl, CURLOPT_CLOSESOCKETFUNCTION, NULL);
> curl_easy_setopt(curl, CURLOPT_CLOSESOCKETDATA, NULL);
>
> Any recommendations/guidance for my use-case?
Not sure I fully understand what you are trying to do. For your understanding:
easy handles use internal connection (which own the socket). There can be many
easy handles using the same connection. With HTTP/1.1 there is only one at a
time, but a connection can be used again for the next easy handle. With HTTP/2
you can have many (commonly up to 100) easy handles per connection.
So, when a transfer is done (easy cleanup), the connection lives on, the socket
stays alive.
Does this explain to you what you are seeing?
- Stefan
>
> On Wed, May 29, 2024 at 2:53 PM Daniel Stenberg <dan...@haxx.se> wrote:
> On Wed, 29 May 2024, Cao Duc Quan via curl-library wrote:
>
> > We plan to add metrics to monitor connectivities such as socket open/close.
> > It seems to me that only CURL APIs support open/close socket callbacks
> > CURLOPT_CLOSESOCKETFUNCTION
> > <https://curl.se/libcurl/c/CURLOPT_CLOSESOCKETFUNCTION.html> but we do not
> > have similar APIs for CURLM.
>
> Right, because the multi handle has no sockets of its own really. Sockets are
> used for transfers and the transfers are held or owned by the easy handles.
>
> So, those are the open/close socket callbacks libcurl provides.
>
> > The problem is that the lifetime of the socket in CURLM maybe longer
> > compared with the easy handle, which means the CURL object could be
> > finished
> > and removed before the socket is closed.
>
> Why is this a problem?
>
> --
>
> / daniel.haxx.se
> | Commercial curl support up to 24x7 is available!
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>
>
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