How to add more than one worker in phoenix app?

Phoenix Forum Questions / Help
1

I want to use MongoDB and ConCaache worker in my app, but when I tried the following

def start(_type, _args) do
    import Supervisor.Spec
    # List all child processes to be supervised
    children = [
      # Start the endpoint when the application starts
      supervisor(MyAppWeb.Endpoint, []),
      # Starts a worker by calling: MyAppWeb.Worker.start_link(arg)
      # {MyAppWeb.Worker, arg},
      worker(Mongo, [[database:
        Application.get_env(:mong, :db)[:name], name: :mongo, pool_size: 100]]),
      worker(ConCache, [name: :my_cache, ttl_check_interval: false])
    ]

I get the following error when running

[info] Application my_app exited: exited in: MyApp.Application.start(:normal, [])
    ** (EXIT) exited in: GenServer.call(:mongo, :topology, 5000)
        ** (EXIT) no process: the process is not alive or there's no process currently associated with the given name, possibly because its
application isn't started
** (Mix) Could not start application my_app: exited in MyApp.Application.start(:normal, [])
    ** (EXIT) exited in: GenServer.call(:mongo, :topology, 5000)
        ** (EXIT) no process: the process is not alive or there's no process currently associated with the given name, possibly because its
application isn't started

What Could I do?

2

This is an old syntax for supervision tree. Which version of Phoenix and Elixir do You use?

3

Elixir 1.10.2

Phoenix v1.4.14

4

There is nothing obviously incorrect with the code example you have shared. Would you be able to share a minimal repoduction of the project so that we can run and debug the problem? Thanks

5

An expanded view of that file might be good too. Are you trying to call Mongo after you define the children within the start function?

6

I have changed the code to this and I don’t know why but it worked perfectly

def start(_type, _args) do
    import Supervisor.Spec
    # List all child processes to be supervised
    children = [
      # Start the endpoint when the application starts
      supervisor(MyAppWeb.Endpoint, []),
      # Starts a worker by calling: MyAppWeb.Worker.start_link(arg)
      # {MyAppWeb.Worker, arg},
      worker(Mongo, [[database:
        Application.get_env(:mong, :db)[:name], name: :mongo, pool_size: 100]]),
     {ConCache, [name: :my_cache, ttl_check_interval: false]}
    ]
7

Now as this has been solved, you should perhaps move to the new supervision syntax. worker and supervisor macros are deprecated since 1.6 or so.

8

could you please refer to a reference?

9

From memory as I can’t use hexdocs on my mobile:

https://hexdocs.pm/elixir/Supervisor.html

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