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MONGOC_CLIENT_POOL_T(3)		   libmongoc	       MONGOC_CLIENT_POOL_T(3)

A connection pool for multi-threaded programs. See Connection Pooling.

SYNOPSIS
	  typedef struct _mongoc_client_pool_t mongoc_client_pool_t

       mongoc_client_pool_t  is	the basis for multi-threading in the MongoDB C
       driver. Since mongoc_client_t  structures  are  not  thread-safe,  this
       structure is used to retrieve a new mongoc_client_t for a given thread.
       This  structure	is  thread-safe,  except  for  its  destructor method,
       mongoc_client_pool_destroy(), which is not thread-safe and must only be
       called from one thread.

EXAMPLE
       example-pool.c

	  /* gcc example-pool.c	-o example-pool	$(pkg-config --cflags --libs
	   * libmongoc-1.0) */

	  /* ./example-pool [CONNECTION_STRING]	*/

	  #include <mongoc/mongoc.h>
	  #include <pthread.h>
	  #include <stdio.h>

	  static pthread_mutex_t mutex;
	  static bool in_shutdown = false;

	  static void *
	  worker (void *data)
	  {
	     mongoc_client_pool_t *pool	= data;
	     mongoc_client_t *client;
	     bson_t ping = BSON_INITIALIZER;
	     bson_error_t error;
	     bool r;

	     BSON_APPEND_INT32 (&ping, "ping", 1);

	     while (true) {
		client = mongoc_client_pool_pop	(pool);
		/* Do something	with client. If	you are	writing	an HTTP	server,	you
		 * probably only want to hold onto the client for the portion of the
		 * request performing database queries.
		 */
		r = mongoc_client_command_simple (client, "admin", &ping, NULL,	NULL, &error);

		if (!r)	{
		   fprintf (stderr, "%s\n", error.message);
		}

		mongoc_client_pool_push	(pool, client);

		pthread_mutex_lock (&mutex);
		if (in_shutdown	|| !r) {
		   pthread_mutex_unlock	(&mutex);
		   break;
		}

		pthread_mutex_unlock (&mutex);
	     }

	     bson_destroy (&ping);
	     return NULL;
	  }

	  int
	  main (int argc, char *argv[])
	  {
	     const char	*uri_string = "mongodb://127.0.0.1/?appname=pool-example";
	     mongoc_uri_t *uri;
	     bson_error_t error;
	     mongoc_client_pool_t *pool;
	     pthread_t threads[10];
	     unsigned i;
	     void *ret;

	     pthread_mutex_init	(&mutex, NULL);
	     mongoc_init ();

	     if	(argc >	1) {
		uri_string = argv[1];
	     }

	     uri = mongoc_uri_new_with_error (uri_string, &error);
	     if	(!uri) {
		fprintf	(stderr,
			 "failed to parse URI: %s\n"
			 "error	message:       %s\n",
			 uri_string,
			 error.message);
		return EXIT_FAILURE;
	     }

	     pool = mongoc_client_pool_new (uri);
	     mongoc_client_pool_set_error_api (pool, 2);

	     for (i = 0; i < 10; i++) {
		pthread_create (&threads[i], NULL, worker, pool);
	     }

	     sleep (10);
	     pthread_mutex_lock	(&mutex);
	     in_shutdown = true;
	     pthread_mutex_unlock (&mutex);

	     for (i = 0; i < 10; i++) {
		pthread_join (threads[i], &ret);
	     }

	     mongoc_client_pool_destroy	(pool);
	     mongoc_uri_destroy	(uri);

	     mongoc_cleanup ();

	     return EXIT_SUCCESS;
	  }

AUTHOR
       MongoDB,	Inc

COPYRIGHT
       2009-present, MongoDB, Inc.

1.30.2				 Apr 12, 2025	       MONGOC_CLIENT_POOL_T(3)

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