How to reliable check if client is really valid

[henning...@celeraone.com]

I have the follwing code

const auto uri_str = "mongodb://wrong:pa...@127.0.0.1:27017/unittest";
//const auto uri_str = "mongodb://foo:b...@127.0.0.1:27017/unittest";

const auto uri = mongocxx::uri{ uri_str };
auto client = mongocxx::client(uri);

if (!client)
{
    std::cerr << "Couldn't connect to DB." << std::endl;
}
else
{
    std::cerr << "Connected to DB!" << std::endl;
}

I try to find out if the client is a vlid client in terms of the authentication of the user. In the example i used two different user which give me the same result. Both result in "Connected to DB!", but the first user is not valid. In the old mongo db c++ driver it was possible to check authentication with auth() on a ScopedDBConnection, but this is not possible anymore. How can i test if the client is valid with the provided URI?

I tried to call the authentication command via the run_command() function as follows

bsoncxx::builder::stream::document auth;
auth << "authenticate"
     << bsoncxx::builder::stream::open_document
     << "user" << "foo"
     << "pwd" << "bar"
     //<< "digestPassword" << false
     //<< "mechanism" << "MONGODB-CR"
     << bsoncxx::builder::stream::close_document;

std::cout << bsoncxx::to_json(auth.view()) << std::endl;

try
{
    auto result = db.run_command(auth.view());
    std::cout << bsoncxx::to_json(result) << std::endl;
}
catch (const mongocxx::exception & e)
{
    std::cerr << "mongocxx::exception - " << e.what() << std::endl;
}

But this always gives me the following error "field missing/wrong type in received authenticate command: generic server error". The documentation for the authentication command is a bit unclear in terms of how the BSON should look like. https://docs.mongodb.com/manual/reference/method/db.auth/#db.auth

Can you tell me how to reliable check if a connection to the database with the supplied information was successful or not and how to call the correctly call the authentication command.

Best regards
Henning

[David Golden]

Generally, the current generation of drivers are designed to succeed during client construction, regardless of the state of servers, so that application startup isn't interrupted by a (possibly transient) server or network error.  Errors (such as authentication problems) are thrown when an operation can't complete.  In your case, try an operation that requires authentication.

Regards,

David

[henning...@celeraone.com]

bool MDB::connected() const
{
    Logger log(LOGGER_NAME);

    if (!client)
    {
        log.e() << "MongoDB connection is not initialized/valid: "
                << uri << " : " << database
                << std::endl;
        return false;
    }

    try
    {
        bsoncxx::builder::stream::document ping;
        ping << "ping" << 1;
        auto db = (**client)[database];
        auto result = db.run_command(ping.view());

        if (result.view()["ok"].get_double() != 1)
        {
            log.e() << "Ping to database failed: "
                    << uri << " : " << database << std::endl;
            return false;

        }
    }
    catch (const mongocxx::exception & e)
    {

        log.e() << "Run command failed: "
                << uri << " : " << database << std::endl;
        return false;
    }

    return true;
}

I know that the authentication is part of the URI, but imagine you have a client in which you are logged in as an admin. Now you want to create a user and than test its access rights. Therefore an authentication method would be good.

[David Golden]

In that circumstance, I recommend creating a new client with the new credentials and trying an operation that requires auth.