:observer.start() don't show worked started by DynamicSupervisor

Questions / Help
1

Here is the worked started by the supervisor
iex(13)> DynamicSupervisor.which_children(Player.Sup)
[
{:undefined, #PID<0.185.0>, :worker, [Ddz.Player]},
{:undefined, #PID<0.400.0>, :worker, [Ddz.Player]},
{:undefined, #PID<0.17547.0>, :worker, [Ddz.Player]}
]
Here is observer display

34%20PM
34%20PM1638×688 32 KB

Why the worker process not displayed?
Thanks for help on this !

2

Can you check the ancestors of the workers?

Process.info(pdi("0.185.0"))


[
  current_function: {Process, :info, 1},
  initial_call: {:proc_lib, :init_p, 5},
  status: :running,
  message_queue_len: 0,
  links: [],
  dictionary: [
    "$initial_call": {IEx.Evaluator, :init, 4},
    "$ancestors": [#PID<0.82.0>],
    iex_evaluator: :ack,
    iex_history: %IEx.History{queue: {[{1, nil}], []}, size: 1, start: 1},
    iex_server: #PID<0.82.0>
  ],
  trap_exit: false,
  error_handler: :error_handler,
  priority: :normal,
  group_leader: #PID<0.65.0>,
  total_heap_size: 8370,
  heap_size: 4185,
  stack_size: 45,
  reductions: 6189,
  garbage_collection: [
    max_heap_size: %{error_logger: true, kill: true, size: 0},
    min_bin_vheap_size: 46422,
    min_heap_size: 233,
    fullsweep_after: 65535,
    minor_gcs: 2
  ],
  suspending: []
]

IIRC, if the ancestors data structure shows up empty, it may mean they are not being linked correctly to you supervisor.

3

You can also try resizing the window :smiley:

1 Like
4

Hi @leiding!

Do you perhaps have a small application that shows the problem?

The issue might perhaps even be because of starting the children the wrong way…

5

Thanks guys, Resize not work, and ancestors shows correctly. Still digging, will update result once I got the answer :slight_smile:

iex(2)> {:ok,pid} =DynamicSupervisor.start_child(Player.Sup,{Ddz.Player, Player1})
{:ok, #PID<0.429.0>}
iex(3)> Process.info(pid)
[
  registered_name: Player1,
  current_function: {:gen_server, :loop, 7},
  initial_call: {:proc_lib, :init_p, 5},
  status: :waiting,
  message_queue_len: 0,
  links: [],
  dictionary: [
    "$initial_call": {Ddz.Player, :init, 1},
    "$ancestors": [Player.Sup, Cards, #PID<0.248.0>]
  ],
  trap_exit: false,
  error_handler: :error_handler,
  priority: :normal,
  group_leader: #PID<0.247.0>,
  total_heap_size: 233,
  heap_size: 233,
  stack_size: 10,
  reductions: 69,
  garbage_collection: [
    max_heap_size: %{error_logger: true, kill: true, size: 0},
    min_bin_vheap_size: 46422,
    min_heap_size: 233,
    fullsweep_after: 65535,
    minor_gcs: 0
  ],
  suspending: []
]
6

Are you creating dynamic supervisors as specified in this guide?

If you follow its instructions, you should have a DynamicSupervisor whose children show up in :observer.start. Then you can compare where your code differs from the one in the examples.

7

Hello everyone,

I have the exact same issue as @leiding. I use elixir 1.9.0 OTP 22. Any news about this ?

I made an example and took a screenshot. Perhaps it can provides complementary information.

dyn_sup_elixir
dyn_sup_elixir1357×763 79.7 KB

Thanks !

8

:wave:

Can you publish the example on github for us to take a look?

9

Sure, here’s the link https://github.com/MrPwet/dynamic-supervisor-example

10

Can you try replacing it with start_link?

2 Likes
11

That solved my issue, indeed. Rookie mistake, I guess…

Thank you for your time !

1 Like