To establish a connection to the server, it is necessary to create an instance of Ndb_cluster_connection, whose constructor takes as its argument a cluster connectstring; if no connectstring is given, localhost is assumed.

The cluster connection is not actually initiated until the Ndb_cluster_connection::connect() method is called. When invoked without any arguments, the connection attempt is retried each 1 second indefinitely until successful, and no reporting is done. See Section 2.3.24, “The Ndb_cluster_connection Class”, for details.

By default an API node will connect to the “nearest” data node — usually a data node running on the same machine, due to the fact that shared memory transport can be used instead of the slower TCP/IP. This may lead to poor load distribution in some cases, so it is possible to enforce a round-robin node connection scheme by calling the set_optimized_node_selection() method with 0 as its argument prior to calling connect(). (See Section 2.3.24.1.6, “Ndb_cluster_connection::set_optimized_node_selection()”.)

The connect() method initiates a connection to a cluster management node only — it does not wait for any connections to data nodes to be made. This can be accomplished by using wait_until_ready() after calling connect(). The wait_until_ready() method waits up to a given number of seconds for a connection to a data node to be established.

In the following example, initialisation and connection are handled in the two functions example_init() and example_end(), which will be included in subsequent examples via the file example_connection.h.

Example 2-1: Connection example. 

#include <stdio.h>
#include <stdlib.h>
#include <NdbApi.hpp>
#include <mysql.h>
#include <mgmapi.h>

Ndb_cluster_connection* connect_to_cluster();
void disconnect_from_cluster(Ndb_cluster_connection *c);

Ndb_cluster_connection* connect_to_cluster()
{
  Ndb_cluster_connection* c;

  if(ndb_init())
    exit(EXIT_FAILURE);

  c= new Ndb_cluster_connection();

  if(c->connect(4, 5, 1))
  {
    fprintf(stderr, "Unable to connect to cluster within 30 seconds.\n\n");
    exit(EXIT_FAILURE);
  }

  if(c->wait_until_ready(30, 0) < 0)
  {
    fprintf(stderr, "Cluster was not ready within 30 seconds.\n\n");
    exit(EXIT_FAILURE);
  }
}

void disconnect_from_cluster(Ndb_cluster_connection *c)
{
  delete c;

  ndb_end(2);
}

int main(int argc, char* argv[])
{
  Ndb_cluster_connection *ndb_connection= connect_to_cluster();

  printf("Connection Established.\n\n");

  disconnect_from_cluster(ndb_connection);

  return EXIT_SUCCESS;
}