Distributed tasks and Nerves

distributed_tasks_and_nerves.md

Distributed tasks and Nerves

The idea was to play around with Nerves and put in practice one of the features Elixir has out of the box: connecting to other existing VM instances, or "nodes".

Here is the exercise I was completing: Our first distributed code

Here are the steps I took to make the above work using Nerves (RPi3 and ethernet):

1 - Use the boilerplate project here (HelloNetwork): https://github.com/nerves-project/nerves_examples/tree/master/hello_network

2 - Make the following edits:

  hello_network [master] :> git diff config/config.exs
  diff --git a/hello_network/config/config.exs b/hello_network/config/config.exs
  index 2601e7c..ef69705 100644
  -  mdns_domain: "hello_network.local"
  +  mdns_domain: "hello_network.local", # This needs a comma, I think the formatter removes it :)

  -# address_method: :dhcp,
  -# ifname: "eth0"
  +  address_method: :dhcp,
  +  ifname: "eth0"

3 - Continue to follow the steps on the readme for the boilerplate project

mix firmware
MIX_TARGET=rpi3 mix firmware.burn

4 - Then, thanks to @jschneck, use the following to create a named IEx session with the correct cookie:

iex --name host@0.0.0.0 --cookie "y3//+WLM8CI7g082flQzSDrSFI72BPRDi69Z9rYthm0DtiiYHj7ioY46ibAQJ9+i"`

Your IEx prompt will look like this:

  iex(host@0.0.0.0)1>

Then, you can connect to the target node:

  iex(host@0.0.0.0)1> Node.connect(:"hello_network@hello_network.local")
  true

And verify that you are connected:

  iex(host@0.0.0.0)2> Node.list
  [:"hello_network@hello_network.local"]

Then you can have some fun by passing messages between the nodes.

Notes:

• hello_network@hello_network.local comes from the below, in config/config.exs:

config :nerves_init_gadget,
  node_name: :hello_network,
  mdns_domain: "hello_network.local",