mongoc_client_t * mongoc_client_pool_pop (mongoc_client_pool_t *pool) BSON_GNUC_WARN_UNUSED_RESULT;
Retrieve a mongoc_client_t from the client pool, or create one. The total number of clients that can be created from this pool is limited by the URI option “maxPoolSize”, default 100. If this number of clients has been created and all are in use,
mongoc_client_pool_pop blocks until another thread returns a client with mongoc_client_pool_push(). If the “waitQueueTimeoutMS” URI option was specified with a positive value, then
mongoc_client_pool_pop will return
NULL when the timeout expires.
pool: A mongoc_client_pool_t.
This function is safe to call from multiple threads.