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.