This script allows you to start a local IEx session and connect it to a remotely running Docker node.
Just clone this repo onto your local machine.
You should ensure that your Elixir and Erlang version installed locally matches that of the docker container that you want to connect to.
By default remote port forwarding (which is used by the script) can only bind to the loopback adapter on the remote host which will not be accessible from a container. To change this edit /etc/ssh/sshd_config on the server and add this line:
GatewayPorts clientspecified
Ensure there are no other GatewayPorts lines in the file. Next, reload the configuration by executing sudo service ssh restart. (These instructions are for Ubuntu, it might be slightly different on other distributions.)
The app must set its node name and a Erlang cookie when it starts.
You will probably be starting your app with something like
mix phoenix.server
To set the node name and cookie you can change it to this
elixir --cookie mycookie --name myapp@127.0.0.1 -S mix phoenix.server
Ensure that the IP is this loopback address.
If you created a release you will probably need to change rel/vm.args file to set the cookie and node name.
Once you have this setup, you should be able to connect to the remote node as follows:
my-laptop$ ./connect-remote.sh me@myserver.com myapp_container myapp
Creating tunnel...Done
Creating local IEx session
Sleeping for 1 second to wait for local IEx session
Erlang/OTP 19 [erts-8.3] [source] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false] [dtrace]
Interactive Elixir (1.4.2) - press Ctrl+C to exit (type h() ENTER for help)
iex(my-laptop@172.17.0.1)1> Remote: connecting to remote node to local node...Connected
Done
nil
iex(my-laptop@172.17.0.1)2> Node.list
[:"myapp@127.0.0.1"]
iex(my-laptop@172.17.0.1)3> You can now switch the IEx session to be on this remote node or start the Observer locally.
The parameters to the connect-remote.sh script are:
- User and hostname of Docker host
- Name of the Docker container running your app
- Name of the node (without the 127.0.0.1) in your container that was set with the
elixir --nameparameter.
Other defaults can be overridden if required by environment variables. Run ./connect-remote.sh -h to get usage.
It starts a local IEx session and then creates an SSH tunnel and forwards the local Erlang EPMD port and port 19000 (for inter-node communication) to the Docker bridge IP on the remote machine.
It then does a docker exec into the running container, creates a second (but temporary) Erlang node in that container, and finally does an RPC to your running app's Erlang node to tell it to connect to your local Erlang node via the forwarded ports.
The SSH tunnel should stay open until the local IEx session is closed.
- While connecting, the formatting of the output from the remote server not print carriage returns correctly. (See example above)