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ADVANCED_CONNECTIONS(3) Library Functions Manual ADVANCED_CONNECTIONS(3)

NAME

Advanced_Connections - None

CONNECTING TO A REPLICA SET

Connecting to a replica set is much like connecting to a standalone MongoDB server. Simply specify the replica set name using the ?replicaSet=myreplset URI option. 

#include <bson.h>
#include <mongoc.h>
int
main (int   argc,
      char *argv[])
{
    mongoc_client_t *client;
    mongoc_init ();
    /* Create our MongoDB Client */
    client = mongoc_client_new ("mongodb://host01:27017,host02:27017,host03:27017/?replicaSet=myreplset");
    /* Do some work */
    /* TODO */
    /* Clean up */
    mongoc_client_destroy (client);
    mongoc_cleanup ();
    return 0;
}

NOTE

Multiple hostnames can be specified in the MongoDB connection string URI, with a comma separating hosts in the seed list.

It is recommended to use a seed list of members of the replica set to allow the driver to connect to any node.

CONNECTING TO A SHARDED CLUSTER

To connect to a sharded cluster , specify the mongos nodes the client should connect to. The C Driver will automatically detect that it has connected to a mongos sharding server.

If more than one hostname is specified, a seed list will be created to attempt failover between the mongos instances.

NOTE

Specifying the replicaSet parameter when connecting to a mongos sharding server is invalid. 

#include <bson.h>
#include <mongoc.h>
int
main (int   argc,
      char *argv[])
{
    mongoc_client_t *client;
    mongoc_init ();
    /* Create our MongoDB Client */
    client = mongoc_client_new ("mongodb://myshard01:27017/");
    /* Do something with client ... */
    /* Free the client */
    mongoc_client_destroy (client);
    mongoc_cleanup ();
    return 0;
}

CONNECTING TO AN IPV6 ADDRESS

The MongoDB C Driver will automatically resolve IPv6 addresses from host names. However, to specify an IPv6 address directly, wrap the address in []

mongoc_uri_t *uri = mongoc_uri_new ("mongodb://[::1]:27017");

CONNECTING TO A UNIX DOMAIN SOCKET

On UNIX‐like systems, the C Driver can connect directly to a MongoDB server using a UNIX domain socket. Simply pass the path to the socket, which must be suffixed with .sock

mongoc_uri_t *uri = mongoc_uri_new ("mongodb:///tmp/mysocket.sock");

NOTE

Connecting directly to a UNIX domain socket is not a common practice.

CONNECTING TO A SERVER OVER SSL

These are instructions for configuring TLS/SSL connections.

To run a server locally (on port 27017, for example): $ mongod --port 27017 --sslMode requireSSL --sslPEMKeyFile server.pem --sslCAFile ca.pem Add /?ssl=true to the end of a client URI.

mongoc_client_t *client = NULL;
client = mongoc_client_new ("mongodb://localhost:27017/?ssl=true");

MongoDB requires client certificates by default, unless the --sslAllowConnectionsWithoutCertificates is provided. The C Driver can be configured to present a client certificate using a mongoc_ssl_opt_t :

const mongoc_ssl_opt_t *ssl_default = mongoc_ssl_opt_get_default ();
mongoc_ssl_opts_t ssl_opts = { 0 };
/* optionally copy in a custom trust directory or file; otherwise the default is used. */
memcpy (&ssl_opts, ssl_default, sizeof ssl_opts);
ssl_opts.pem_file = "client.pem" 
mongoc_client_set_ssl_opts (client, &ssl_opts);
The client certificate provided by pem_file must be issued by one of the server trusted Certificate Authorities listed in --sslCAFile , or issued by a CA in the native certificate store on the server when omitted.

To verify the server certificate against a specific CA, provide a PEM armored file with a CA certificate, or contatinated list of CA certificates using the ca_file option, or c_rehash directory structure of CAs, pointed to using the ca_dir option. When no ca_file or ca_dir is provided, the driver will use CAs provided by the native platform certificate store.

See for more information on the various SSL related options.

ADDITIONAL CONNECTION OPTIONS

A variety of connection options for the MongoDB URI can be found here

COLOPHON

This page is part of MongoDB C Driver. Please report any bugs at https://jira.mongodb.org/browse/CDRIVER.
2016‐10‐12 MongoDB C Driver