Access Your Database Remotely Through an SSH Tunnel

Your database instance is not directly accessible from outside the environment. This is a good thing because a database cannot reliably maintain the security and patch levels like SSH can. However, it means that to access your database from an external database tool, such as pgAdmin, MySQL Workbench, or SQLyog, you need to create an SSH tunnel to your database host/instance.

For example, you want to run pgAdmin or MySQL Workbench on your laptop and you want to use this tool to examine your application database: You create an SSH tunnel from your laptop (the local) to your database instance (the remote) on Engine Yard Cloud.

You can also use SSH tunnels to set up offsite replication.

This page describes:

  • Prerequisites
  • Create an SSH tunnel manually
  • Create a SSH tunnel in the background with a custom Chef recipe

About SSH tunnels

An SSH tunnel links a port on your local machine to a port on a remote host. When these ports are linked, anything communicated to the local port is passed through SSH to the remote port; likewise, any communication to the remote port is passed back through SSH to the local port. The added benefit of this setup is that the communications between your local machine and the remote host is encrypted by the SSH connection.

Use MySQL Workbench to connect to MySQL Server

As an alternative to setting up an SSH tunnel manually, you can use MySQL Workbench to connect to a MySQL Server using TCP/IP over an SSH connection. See MySQL Workbench for more information.

Set-up SSH Keys

Before you can set up your SSH tunnel, you need to ensure that you have configured and installed SSH keys on your running environment.

  • UNIX-based systems

  • Windows-based systems

Create the SSH tunnel manually

The syntax for creating the SSH tunnel is ssh -L [local port]:[database host]:[remote port] \
[username]@[remote host]

  • [local port] The local port your database tool connects to.
    If you have a MySQL installation on your local machine, it runs on port 3306 by default; therefore, don’t use 3306 for the local port. For example, use 3307 instead.
    If you have a PostgreSQL installation on your local machine, it runs on port 5432 by default; therefore, don’t use 5432 for the local port. For example, use 5433 instead.

  • [database host] The hostname or IP address of the database instance that you are tunneling to. If the [remote host] is the database instance you will want to set this to 127.0.0.1 (so it refers to itself). If you used an application instance as [remote host] then you can use the value of "host:" from your database.yml instead.

  • [remote port] The port that your remote database listens for connections on.
    For MySQL databases, this is 3306 by default.
    For PostgreSQL database, this is 5432 by default.

  • [username] the user for the database instance. The default user for the Engine Yard Cloud database is deploy.

  • [remote host] the remote instance your tunnel will connect to the database through. This can be the database instance itself, or any instance within the database environment.

The tunneling command opens an SSH session with the [remote host] specified. The tunnel will work as long as that SSH session is active. If the session window is consuming valuable workspace we recommend minimizing it as running tunnels in the background can lead to multiple tunnels and port conflicts.

To create and test the SSH tunnel for a MySQL database

  1. In a terminal window on your local machine, type:

    ssh -L 3307:ec2-172-16-139-19.us-west-1.compute.amazonaws.com:3306 \
    deploy@ec2-174-129-17-196.compute-1.amazonaws.com

    where
    3307 is the local port,
    ec2-172-16-139-19.us-west-1.compute.amazonaws.com is the database host,
    3306 is the listening port, 
    deploy is the database username, and
    ec2-174-129-17-196.compute-1.amazonaws.com is the remote host.

  2. Before connecting the external database tool such as MySQL Workbench or SQLyog, test the connection with a simple tool such as the database console, mysql.
    (Your tunnel needs to be running for this test.)

    Type

    mysql -udeploy -p -P 3307 -h 127.0.0.1 

    where
    deploy is the database username on the remote host and 
    3307 is the local port.

    You are prompted for your database password.

    Note: for the -h argument, it is necessary to use 127.0.0.1 instead of localhost.

To create and test the SSH tunnel for a PostgreSQL database

  1. In a terminal window on your local machine, type

    ssh -L 5433:ec2-172-16-139-19.us-west-1.compute.amazonaws.com:5432 \
    deploy@ec2-174-129-17-196.compute-1.amazonaws.com

    where
    5433 is the local port,
    ec2-172-16-139-19.us-west-1.compute.amazonaws.com is the database host,
    5432 is the listening port, 
    deploy is the database username, and
    ec2-174-129-17-196.compute-1.amazonaws.com is the remote host.

  2. Before connecting the external database tool such as pgAdmin, test the connection with a simple tool such as the database console psql.
    (Your tunnel needs to be running for this test.)

    Type

    psql -Udeploy -d myapp -p 5433 -h 127.0.0.1

    where
    deploy is the database username on the remote host and 
    5433 is the local port.

    You are prompted for your database password.

Setting up an SSH tunnel using a custom Chef recipe

The procedure above explained how to set up the SSH tunnel manually.

An alternate way to set up an SSH tunnel is through this custom cookbook: //github.com/engineyard/ey-cloud-recipes/tree/master/cookbooks/ssh_tunnel

This recipe installs:

  • An init script that sets up the SSH tunnel from the instance in the background
  • A config file to have monit watch over the tunnel and keep it open

To create an SSH tunnel using the Engine Yard ssh_tunnel custom Chef recipe

  • Follow the instructions in the recipe and in Customize your environment with Chef recipes.