threaded-shared-conn.c: new example

docs/examples/Makefile.inc

@@ -34,7 +34,7 @@ check_PROGRAMS = 10-at-a-time anyauthput cookie_interface debug fileupload \
   imap-tls imap-multi url2file sftpget ftpsget postinmemory http2-download \
   http2-upload http2-serverpush getredirect ftpuploadfrommem               \
   ftpuploadresume sslbackend postit2-formadd multi-formadd                 \
-  shared-connection-cache
+  shared-connection-cache threaded-shared-conn
 
 # These examples require external dependencies that may not be commonly
 # available on POSIX systems, so don't bother attempting to compile them here.

docs/examples/threaded-shared-conn.c

@@ -0,0 +1,156 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+/* <DESC>
+ * Multi-threaded transfers sharing a single connection pool
+ * </DESC>
+ *
+ * This example fires up NUM_THREADS threads and in each single thread, it
+ * downloads the same fixed URL a URL_ITERATIONS number of times. The received
+ * data is just thrown away. It sets up a single shared object that holds the
+ * connection cache and all easy threads in all threads share that same cache.
+ *
+ * This example uses pthreads for threads and mutexes, but should be easy to
+ * modify to use different thread/mutex system should you want to.
+ *
+ */
+
+#include <stdio.h>
+#include <pthread.h>
+#include <curl/curl.h>
+
+/*
+  URL to fetch. If you select HTTPS, you need to use a TLS backend with mutex
+  locks taken care of (OpenSSL 1.1.x, NSS, etc) or add SSL mutex callbacks!
+*/
+#define URL "http://localhost/4KB"
+
+/* number of threads to fire up in parallel */
+#define NUM_THREADS 67
+
+/* how many times each URL is transferred per thread */
+#define URL_ITERATIONS 11235
+
+static pthread_mutex_t connlock;
+
+static size_t write_db(void *ptr, size_t size, size_t nmemb, void *data)
+{
+  /* not interested in the downloaded bytes, return the size */
+  (void)ptr;  /* unused */
+  (void)data; /* unused */
+  return (size_t)(size * nmemb);
+}
+
+static void lock_cb(CURL *handle, curl_lock_data data,
+                    curl_lock_access access, void *userptr)
+{
+  (void)access; /* unused */
+  (void)userptr; /* unused */
+  (void)handle; /* unused */
+  (void)data; /* unused */
+  pthread_mutex_lock(&connlock);
+}
+
+static void unlock_cb(CURL *handle, curl_lock_data data,
+                      void *userptr)
+{
+  (void)userptr; /* unused */
+  (void)handle;  /* unused */
+  (void)data;    /* unused */
+  pthread_mutex_unlock(&connlock);
+}
+
+static void init_locks(void)
+{
+  pthread_mutex_init(&connlock, NULL);
+}
+
+static void kill_locks(void)
+{
+  pthread_mutex_destroy(&connlock);
+}
+
+struct initurl {
+  const char *url;
+  CURLSH *share;
+  int threadno;
+};
+
+static void *run_thread(void *ptr)
+{
+  struct initurl *u = (struct initurl *)ptr;
+  int i;
+
+  for(i = 0; i < URL_ITERATIONS; i++) {
+    CURL *curl = curl_easy_init();
+    curl_easy_setopt(curl, CURLOPT_URL, u->url);
+    curl_easy_setopt(curl, CURLOPT_VERBOSE, 0L);
+    curl_easy_setopt(curl, CURLOPT_SHARE, u->share);
+    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_db);
+    curl_easy_perform(curl); /* ignores error */
+    curl_easy_cleanup(curl);
+    fprintf(stderr, "Tread %d transfer %d\n", u->threadno, i);
+  }
+
+  return NULL;
+}
+
+int main(void)
+{
+  pthread_t tid[NUM_THREADS];
+  int i;
+  int error;
+  CURLSH *share;
+  struct initurl url[NUM_THREADS];
+
+  /* Must initialize libcurl before any threads are started */
+  curl_global_init(CURL_GLOBAL_ALL);
+
+  share = curl_share_init();
+  curl_share_setopt(share, CURLSHOPT_LOCKFUNC, lock_cb);
+  curl_share_setopt(share, CURLSHOPT_UNLOCKFUNC, unlock_cb);
+  curl_share_setopt(share, CURLSHOPT_SHARE, CURL_LOCK_DATA_CONNECT);
+
+  init_locks();
+
+  for(i = 0; i< NUM_THREADS; i++) {
+    url[i].url = URL;
+    url[i].share = share;
+    url[i].threadno = i;
+    error = pthread_create(&tid[i], NULL, run_thread, &url[i]);
+    if(0 != error)
+      fprintf(stderr, "Couldn't run thread number %d, errno %d\n", i, error);
+    else
+      fprintf(stderr, "Thread %d, gets %s\n", i, URL);
+  }
+
+  /* now wait for all threads to terminate */
+  for(i = 0; i< NUM_THREADS; i++) {
+    error = pthread_join(tid[i], NULL);
+    fprintf(stderr, "Thread %d terminated\n", i);
+  }
+
+  kill_locks();
+
+  curl_share_cleanup(share);
+  curl_global_cleanup();
+  return 0;
+}