Specs

start_child(
  Supervisor.supervisor(),
  Supervisor.child_spec()
  | {module(), term()}
  | module()
  | (old_erlang_child_spec :: :supervisor.child_spec())
) :: on_start_child()

Dynamically adds a child specification to supervisor and starts that child.

child_spec should be a valid child specification as detailed in the "Child specification" section of the documentation for Supervisor. The child process will be started as defined in the child specification.

If the child process start function returns {:ok, child} or {:ok, child, info}, then child specification and PID are added to the supervisor and this function returns the same value.

If the child process start function returns :ignore, then no child is added to the supervision tree and this function returns :ignore too.

If the child process start function returns an error tuple or an erroneous value, or if it fails, the child specification is discarded and this function returns {:error, error} where error is the error or erroneous value returned from child process start function, or failure reason if it fails.

If the supervisor already has N children in a way that N exceeds the amount of :max_children set on the supervisor initialization (see init/1), then this function returns {:error, :max_children}.