View Source Plug.Cowboy.Drainer (Plug.Cowboy v2.6.1)

Process to drain cowboy connections at shutdown.

When starting Plug.Cowboy in a supervision tree, it will create a listener that receives requests and creates a connection process to handle that request. During shutdown, a Plug.Cowboy process will immediately exit, closing the listener and any open connections that are still being served. However, in most cases, it is desirable to allow connections to complete before shutting down.

This module provides a process that during shutdown will close listeners and wait for connections to complete. It should be placed after other supervised processes that handle cowboy connections.



The following options can be given to the child spec:

  • :refs - A list of refs to drain. :all is also supported and will drain all cowboy listeners, including those started by means other than Plug.Cowboy.

  • :id - The ID for the process. Defaults to Plug.Cowboy.Drainer.

  • :shutdown - How long to wait for connections to drain. Defaults to 5000ms.

  • :check_interval - How frequently to check if a listener's connections have been drained. Defaults to 1000ms.



# In your application
def start(_type, _args) do
  children = [
    {Plug.Cowboy, scheme: :http, plug: MyApp, options: [port: 4040]},
    {Plug.Cowboy, scheme: :https, plug: MyApp, options: [port: 4041]},
    {Plug.Cowboy.Drainer, refs: [MyApp.HTTP, MyApp.HTTPS]}

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