CODEWITHSUNDEEP
elixirphoenix-frameworkerlang-otp
9_Dave_9
9_Dave_9

Reputation: 714

Elixir Redix name-based pool example - Supervisor signature doesn't exist

So I am having trouble following this "super simple" example. New to Elixir(From a Ruby background predominantly).

Just trying to create a pool of redis connections setup under the main application supervision tree to use for active user sessions but in truth redis is going to be a lot more useful down the line so I am trying to get this setup right.

This line:
start: {Supervisor, :start_link, [children_redix]}

 Gives me the following error:

** (Mix) Could not start application gametime: 
Gametime.Application.start(:normal, []) returned an error: shutdown: 
failed to start child: RedixSupervisor
** (EXIT) an exception was raised:
    ** (UndefinedFunctionError) function Supervisor.start_link/1 is undefined or private
        (elixir) Supervisor.start_link([%{id: {Redix, 0}, start: {Redix, :start_link, [[name: :redix_0]]}, type: :worker}, %{id: {Redix, 1}, start: {Redix, :start_link, [[name: :redix_1]]}, type: :worker}, %{id: {Redix, 2}, start: {Redix, :start_link, [[name: :redix_2]]}, type: :worker}, %{id: {Redix, 3}, start: {Redix, :start_link, [[name: :redix_3]]}, type: :worker}, %{id: {Redix, 4}, start: {Redix, :start_link, [[name: :redix_4]]}, type: :worker}])

and if I remove the square brackets from the children_redix on the above line I get:

 ** (UndefinedFunctionError) function Supervisor.start_link/5 is undefined or private

This is the documentation I am following:

https://hexdocs.pm/redix/real-world-usage.html

This is the application start function:

   defmodule Gametime.Application do                                                            
      use Application                                                                            
      use Supervisor                                                                           


      def start(_type, _args) do                                                                 

        pool_size = 5                                                                            

        #creates redix children processes                                                                                   
        children_redix =                                                                         
          for i <- 0..(pool_size - 1) do                                                         
            Supervisor.child_spec({Redix, name: :"redix_#{i}"}, id: {Redix, i})                  
          end                                                                                    

        children = [                                                                             
          # child spec for the supervisor I am trying to add to the main supervision tree,                                                                                
          %{                                                                                     
            id: RedixSupervisor,                                                                 
            type: :supervisor,                                                                   
            start: {Supervisor, :start_link, [children_redix]}                                   
          },                                                                                     

          # This way is now deprecated  - although this was generated by phoenix so not going to touch this just yet.                                       
          supervisor(Gametime.Repo, []),                                                                                    
          supervisor(GametimeWeb.Endpoint, []),                                                  

          # Start your own worker by calling: Gametime.Worker.start_link(arg1, arg2, arg3)       
          # worker(Gametime.Worker, [arg1, arg2, arg3]),                                         
        ]                                                                                        


        opts = [strategy: :one_for_one, name: Gametime.Supervisor]                                                                                             
        Supervisor.start_link(children, opts)                                                    
      end

I'm just not sure where I am going wrong. I feel like it may be an assumption being made in the docs as to what I should know - but I don't know what I don't know unfortunately. Any help would be awesome - cheers.

Upvotes: 2

Views: 714

Answers (2)

9_Dave_9
9_Dave_9

Reputation: 714

oh wow - so I guess the docs are outdated. Went through some pain to figure this out - so thought I would share. 

...   %{                                                                                                
      id: RedixSupervisor,                                                                            
      type: :supervisor,                                                                              
      start: {Supervisor, :start_link, [  children_redix , [strategy: :one_for_one] ]}                                                                        
    },  ...

is the answer. The docs seem to just pass the children_redix child_spec maps - but this isn't what Supervisor.start_link/2 expects as a signature.

I might be missing more to the story and again there could be something in the how to that I am not picking up due to a possible assumption of what people should already be aware of.

cheers

Upvotes: 2

m3characters
m3characters

Reputation: 2290

You probably need to wrap:

Supervisor.child_spec(%{ id: RedixSupervisor, type: :supervisor, start: {RedixSupervisor, :start_link, [children_redix]} })

And on the start tuple use your RedixSupervisor module, and not the generic Supervisor. From the start_link/1 defined in RedixSupervisor, where you'll receive the arguments (in this case, children_redix) is where you'll Supervisor.start_link, and use the children passed as the argument in the init function

An example would be:

defmodule RedixSupervisor do
  use Supervisor
  require Logger

  def start_link(children_redix) do
    Logger.info("RedixSupervisor Start Link")
    Supervisor.start_link(__MODULE__, children_redix, name: __MODULE__)
  end

  def init(children_redix) do
    children = children_redix
    Supervisor.init(children, strategy: :one_for_one)
  end
end

Upvotes: 0

Related Questions