malte
Absinthe subscriptions broken?
I’m trying to use subscriptions in Absinthe, but keep getting this error when I try to start the server:
** (Mix) Could not start application pb: exited in: Pb.Application.start(:normal, [])
** (EXIT) an exception was raised:
** (FunctionClauseError) no function clause matching in Absinthe.Subscription.child_spec/1
(absinthe) lib/absinthe/subscription.ex:43: Absinthe.Subscription.child_spec(PbWeb.Endpoint)
(elixir) lib/supervisor.ex:624: Supervisor.init_child/1
(elixir) lib/enum.ex:1336: Enum."-map/2-lists^map/1-0-"/2
(elixir) lib/enum.ex:1336: Enum."-map/2-lists^map/1-0-"/2
(elixir) lib/supervisor.ex:615: Supervisor.init/2
(elixir) lib/supervisor.ex:564: Supervisor.start_link/2
(kernel) application_master.erl:277: :application_master.start_it_old/4
This is in a completely vanilla app, freshly created using:
mix phx.new pb --no-html
cd pb
mix ecto.create
Then following the directions here: absinthe/guides/subscriptions.md at main · absinthe-graphql/absinthe · GitHub
I’m following the directions for 1.4.x
And then doing
iex -S mix phx.server
Does anyone know why it breaks for me?
Marked As Solved
idi527
Can you post your lib/application.ex here? Judging by the error alone, there is a problem at absinthe/lib/absinthe/subscription.ex at v1.4 · absinthe-graphql/absinthe · GitHub so it’d be helpful to see how you define the children for the supervisor.
According to the guide for version 1.4 it should be like this:
[
# other children ...
supervisor(MyAppWeb.Endpoint, []), # this line should already exist
supervisor(Absinthe.Subscription, [MyAppWeb.Endpoint]), # add this line
# other children ...
]
On the master branch they’ve added the child_spec approach but note that the guide doesn’t include it. I’d try something like
[
# Start the Ecto repository
MyAppWeb.Repo,
# Start the endpoint when the application starts
MyAppWeb.Endpoint,
{Absinthe.Subscription, [MyAppWeb.Endpoint]} # <-- note this is different from the guide
]
since in v1.4 child_spec expects a list, not a single module atom.
Also Liked
malte
Actually, the supervisor(...) calls are for 1.3 from what I understand, because in 1.4 the direct call to supervisor() has been supplanted by doing Supervisor.start_link(...).
So on the page I linked above (from absinthe-graphql’s github repo), it says to add it like so:
{Absinthe.Subscription, PbWeb.Endpoint} to the children list. Doing this results in the problem I reported above.
However, doing what you suggest fixes the issue! So in case this may help others, here is what the relevant part of my application.ex looks like:
# List all child processes to be supervised
children = [
# Start the Ecto repository
Pb.Repo,
# Start the endpoint when the application starts
PbWeb.Endpoint,
# Starts a worker by calling: Pb.Worker.start_link(arg)
# {Pb.Worker, arg},
{Absinthe.Subscription, [PbWeb.Endpoint]}
]
# See https://hexdocs.pm/elixir/Supervisor.html
# for other strategies and supported options
opts = [strategy: :one_for_one, name: Pb.Supervisor]
Supervisor.start_link(children, opts)
end
Thank you very much, idiot!
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