View Source Getting started

In this guide we will go through the basic usage of ProcessHub and how to integrate it in your application.

To get more familiar with the public API of ProcessHub, please refer to the ProcessHub module.

Installation

In order to use ProcessHub in your application, you need to add it as a dependency. Once you have added it as a dependency, you need to start the ProcessHub master supervisor. It is highly recommended to start the ProcessHub supervisor under your application supervision tree.

1. Add process_hub to your list of dependencies in mix.exs:

    def deps do
        [
            {:process_hub, "~> 0.4.0-beta"}
        ]
    end

2. Pull the dependency:

    mix deps.get
   

3. Start the ProcessHub supervisor under your application supervision tree:

    defmodule MyApp.Application do
        use Application
   
        def start(_type, _args) do
            children = [
                ProcessHub.child_spec(%ProcessHub{hub_id: :my_hub})
            ]
   
            opts = [strategy: :one_for_one, name: MyApp.Supervisor]
            Supervisor.start_link(children, opts)
        end
    end

Hub ID

Each node in the cluster that starts a ProcessHub instance and shares the same :hub_id will form a hub cluster.

It is possible to start multiple hubs under the same supervision tree with different configuration options, in this case, each hub must have a unique :hub_id.

Example usage

The following example shows how to start 2 elixir nodes, connect them and start processes under the ProcessHub cluster. This demonstrates how the processes are distributed in the cluster.

Note: The examples below assume that the ProcessHub is already started under the supervision tree. If not please refer to the Installation section.

Note: Make sure you have a GenServer module called MyProcess defined in your project.

defmodule MyProcess do
    use GenServer

    def start_link(_) do
        GenServer.start_link(__MODULE__, nil)
    end

    def init(_) do
        {:ok, nil}
    end
end

Node 1

Start the first node with the following command:

iex --name node1@127.0.0.1 --cookie mycookie -S mix

# Run the following in the iex console to start 5 processes under the hub.
iex> ProcessHub.start_children(:my_hub, [
...>    %{id: :process1, start: {MyProcess, :start_link, [nil]}},
...>    %{id: :process2, start: {MyProcess, :start_link, [nil]}},
...>    %{id: :process3, start: {MyProcess, :start_link, [nil]}},
...>    %{id: :process4, start: {MyProcess, :start_link, [nil]}},
...>    %{id: :process5, start: {MyProcess, :start_link, [nil]}}
...> ])
{:ok, :start_initiated}

# Check the started processes by running the command below.
iex> ProcessHub.process_list(:my_hub, :global)
[
  process1: ["node1@127.0.0.1": #PID<0.256.0>],
  process2: ["node1@127.0.0.1": #PID<0.257.0>],
  process3: ["node1@127.0.0.1": #PID<0.258.0>],
  process4: ["node1@127.0.0.1": #PID<0.259.0>],
  process5: ["node1@127.0.0.1": #PID<0.260.0>]
]

Node 2

We will use this node to connect to the first node and see how the processes are automatically distributed.

Start the second node.

iex --name node2@127.0.0.1 --cookie mycookie -S mix

# Connect the second node to the first node.
iex> Node.connect(:"node1@127.0.0.1")
true

# Check the started procsses by running the command below and
# see how some of the processes are distributed to the second node.
iex> ProcessHub.process_list(:my_hub, :global)
[
  process4: ["node2@127.0.0.1": #PID<0.285.0>],
  process3: ["node2@127.0.0.1": #PID<0.284.0>],
  process1: ["node2@127.0.0.1": #PID<0.283.0>],
  process2: ["node1@127.0.0.1": #PID<23045.257.0>],
  process5: ["node1@127.0.0.1": #PID<23045.260.0>]
]