MarcoPolo - Server Operations

OrientDB differentiates between connections made to the database and connections made to the server. While you can get both from the start_link() function in MarcoPolo, which you choose determines the kinds of operations you can perform. Server operations including creating and dropping databases, and checking that they exist.

Connecting to the Server

In order to operate on the server, you first need to connect to it. To manage this, call the start_link() function, then pass :server to the connection parameter. For instance.

@doc """ Connect to OrientDB Server """
def orientdb_server(user, passwd) ::
    {:ok, conn } = MarcoPolo.start_link(
        user: user, password: passwd, connection: :server)
end

Using Server Connections

When you call the start_live() function, it returns a connection interface to your application, which by convention is called conn here. With the connection interface initialized to your OrientDB Server, there are a number of operations that become available by passing the conn value to MarcoPolo functions.

@doc """ Check if Database Exists, Create it if it does not """
def create_db(conn, dbname, type) when type in [:plocal, :memory] do

    # Check Database Existence
    unless MarcoPolo.db_exists?(conn, dbname, type) do

        # Log Operation
        IO.puts("Creating Database: #{dbname}")

        # Create Database
        MarcoPolo.db_create(conn, dbname, :document, type)

    end
end

Closing Connections

When you are finished with a connection, whether the connection interface was opened on a database or a server, you can close the connection and free up resources by calling the stop() function.

For instance, consider the use case of a web application that operates on several databases on an OrientDB server. You might want a function to loop over a series of database names, determining whether or not they exist and creating them where they don't, then close the connection once this operation is complete.

@doc """ Takes connection and list of databases and creates those that don't exist. """
def create_databases(user, passwd, databases) do

    # Open Connection
    IO.puts("Connecting to OrientDB Server")
    {:ok, conn} = MarcoPolo.start_link(
        user: user,
        password: passwd,
        connect: :server)

    # Loop Over Databases
    for db <- databases do

        # Check Existence
        IO.puts("Database Test: #{db}")
        unless MarcoPolo.exists(conn, db, :graph, :plocal) do

            # Create Database
            IO.puts("Database #{db} not found, creating...")
            MarcoPolo.create_db(conn, db, :graph, :plocal)

        end
    end

    # Close Connection
    IO.puts("Closing Server Connection")
    MarcoPolo.stop(conn)

end