My app crashes at the start

kattair0ta8

All of a sudden my app has started to crash:

    $ mix phx.server
    [................]

    Generated my_app app
    [info] Application my_app exited: MyApp.Application.start(:normal, []) returned an error: shutdown: failed to start child: MyAppWeb.Endpoint
        ** (EXIT) shutdown: failed to start child: Phoenix.Endpoint.Handler
            ** (EXIT) an exception was raised:
                ** (UndefinedFunctionError) function Phoenix.Endpoint.Cowboy2Handler.child_spec/3 is undefined (module Phoenix.Endpoint.Cowboy2Handler is not available)
                    Phoenix.Endpoint.Cowboy2Handler.child_spec(:http, MyAppWeb.Endpoint, [port: 4000, otp_app: :my_app])
                    (phoenix) lib/phoenix/endpoint/handler.ex:33: anonymous fn/5 in Phoenix.Endpoint.Handler.init/1
                    (elixir) lib/enum.ex:1925: Enum."-reduce/3-lists^foldl/2-0-"/3
                    (phoenix) lib/phoenix/endpoint/handler.ex:31: Phoenix.Endpoint.Handler.init/1
                    (stdlib) supervisor.erl:295: :supervisor.init/1
                    (stdlib) gen_server.erl:374: :gen_server.init_it/2
                    (stdlib) gen_server.erl:342: :gen_server.init_it/6
                    (stdlib) proc_lib.erl:249: :proc_lib.init_p_do_apply/3
    ** (Mix) Could not start application my_app: MyApp.Application.start(:normal, []) returned an error: shutdown: failed to start child: MyAppWeb.Endpoint
        ** (EXIT) shutdown: failed to start child: Phoenix.Endpoint.Handler
            ** (EXIT) an exception was raised:
                ** (UndefinedFunctionError) function Phoenix.Endpoint.Cowboy2Handler.child_spec/3 is undefined (module Phoenix.Endpoint.Cowboy2Handler is not available)
                    Phoenix.Endpoint.Cowboy2Handler.child_spec(:http, MyAppWeb.Endpoint, [port: 4000, otp_app: :my_app])
                    (phoenix) lib/phoenix/endpoint/handler.ex:33: anonymous fn/5 in Phoenix.Endpoint.Handler.init/1
                    (elixir) lib/enum.ex:1925: Enum."-reduce/3-lists^foldl/2-0-"/3
                    (phoenix) lib/phoenix/endpoint/handler.ex:31: Phoenix.Endpoint.Handler.init/1
                    (stdlib) supervisor.erl:295: :supervisor.init/1
                    (stdlib) gen_server.erl:374: :gen_server.init_it/2
                    (stdlib) gen_server.erl:342: :gen_server.init_it/6
                    (stdlib) proc_lib.erl:249: :proc_lib.init_p_do_apply/3

I’m using and have been using for a while the latest versions of everything: Cowboy - 2.5, Phoenix - 1.3. All has been working fine for over a half a year

41 comments

/phoenix #cowboy #troubleshooting

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2020-03-19 20:22:32 UTC

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OvermindDL1

Well this is definitely the issue. Cowboy2 handler means that something was updated very recently and not everything was updated entirely and properly and/or _build got corrupted, in which case wipe and rebuild?

Post #1

kattair0ta8

removed _build and recompiled – didn’t help

Post #2

cdfuller

Change your cowboy dependency to {:plug_cowboy, "~> 1.0"}.

Post #3

OvermindDL1

They said they were already using cowboy2 successfully so that shouldn’t be needed.

Can you post your mix.exs file so I can drop it into a new project to give it a try?

Post #4

kattair0ta8

  defp deps do
    [
      
      {:phoenix, github: "phoenixframework/phoenix", override: true},
      # {:phoenix, github: "phoenixframework/phoenix"},
      # {:phoenix, "~> 1.3.4"},


      {:phoenix_pubsub, "~> 1.1"},
      {:phoenix_ecto, "~> 3.5"},
      {:postgrex, "~> 0.13.5"},
      {:phoenix_html, "~> 2.12"},
      {:phoenix_live_reload, "~> 1.1", only: :dev},
      {:gettext, "~> 0.16"},
      {:cowboy, "~> 2.5", override: true},
      {:yamerl, "~> 0.7"},
      {:earmark, "~> 1.2"},
      {:edeliver, "~> 1.6"},
      {:distillery, "~> 2.0"},
      {:httpoison, "~> 1.4"},
      {:swoosh, "~> 0.20"},
      {:gen_smtp, "~> 0.13"},


      # {:poison, "~> 4.0.1"},
      # {:poison, "~> 4.0.1", override: true},
      {:poison, "~> 3.1"},
    ]
  end

Post #5

cdfuller

The module Plug.Adapters.Cowboy2 was deprecated a few days ago and it’s now recommended to use {:plug_cowboy, "~> 2.0"} for cowboy 2.0

https://hexdocs.pm/plug/Plug.Adapters.Cowboy2.html

I ran into the same or similar problem yesterday and this is how I was able to solve it.

Post #6

kattair0ta8

Why and how did it use to work without plug_cowboy at all in my project?

phoenix 1.3.4 of August 2018 - doesn’t work now either

Post #7

Gazler

Phoenix Core Team

Cowboy 2 is only supported on Phoenix 1.4.0-rc.2 and above via {:plug_cowboy, "~> 2.0"}

It is likely that you have updated plug to 1.7 in which case you will be prompted to replace cowboy with {:plug_cowboy, "~> 1.0"} in your mix.exs file.

Post #8