When an error is raised in the subscribed method of an ActionCable channel, it does no

only public actions declared by the user are rescue-able </blockquote

rescue_from not working with subscribed method on ActionCable channel,about rails/rails

zzak commented on September 26, 2024 1

It looks like for channels, only public actions declared by the user are rescue-able and not callbacks like #subscribed:

rails/actioncable/lib/action_cable/channel/base.rb

Lines 173 to 187 in 965b8c3

    
           # Extract the action name from the passed data and process it via the channel. 
        
           # The process will ensure that the action requested is a public method on the 
        
           # channel declared by the user (so not one of the callbacks like #subscribed). 
        
           def perform_action(data) 
        
             action = extract_action(data) 
        
             if processable_action?(action) 
        
               payload = { channel_class: self.class.name, action: action, data: data } 
        
               ActiveSupport::Notifications.instrument("perform_action.action_cable", payload) do 
        
                 dispatch_action(action, data) 
        
               end 
        
             else 
        
               logger.error "Unable to process #{action_signature(action, data)}" 
        
             end 
        
           end

For connections since the test works, I think there isn't a problem here.
There is already a test for this:

rails/actioncable/test/connection/subscriptions_test.rb

Lines 116 to 127 in 965b8c3

    
           test "accessing exceptions thrown during command execution" do 
        
             run_in_eventmachine do 
        
               setup_connection 
        
               subscribe_to_chat_channel 
        
               data = { "content" => "Hello World!", "action" => "throw_exception" } 
        
               @subscriptions.execute_command "command" => "message", "identifier" => @chat_identifier, "data" => ActiveSupport::JSON.encode(data) 
        
               exception = @connection.exceptions.first 
        
               assert_kind_of ChatChannelError, exception 
        
             end 
        
           end

Maybe we could add a test for not supporting rescue_from in non-user callbacks (like subscribed).

from rails.

Buitragox commented on September 26, 2024

only public actions declared by the user are rescue-able

Looks like only #subscribed and #unsubscribed are not rescue-able.

You can still use rescue_from by doing something like this:

def subscribed
    # ...
rescue StandardError => e
    rescue_with_handler(e)
end

But I still find it a bit confusing that these two actions are exceptions to rescue_from, as their behavior is defined inside the channel.

This is the current #subscribe_to_channel method which calls #subscribed:

rails/actioncable/lib/action_cable/channel/base.rb

Lines 191 to 198 in 965b8c3

    
           def subscribe_to_channel 
        
             run_callbacks :subscribe do 
        
               subscribed 
        
             end 
        
             reject_subscription if subscription_rejected? 
        
             ensure_confirmation_sent 
        
           end

Maybe using rescue_with_handler in this method could be a good solution?

def subscribe_to_channel
  run_callbacks :subscribe do
    subscribed
  end
rescue Exception => exception
  rescue_with_handler(exception) || raise
ensure
  reject_subscription if subscription_rejected?
  ensure_confirmation_sent
end

And something similar with #unsubscribe_from_channel.

from rails.

rails-bot commented on September 26, 2024

This issue has been automatically marked as stale because it has not been commented on for at least three months.
The resources of the Rails team are limited, and so we are asking for your help.
If you can still reproduce this error on the 7-2-stable branch or on main, please reply with all of the information you have about it in order to keep the issue open.
Thank you for all your contributions.

from rails.

rescue_from not working with subscribed method on ActionCable channel about rails HOT 3 CLOSED

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	# Extract the action name from the passed data and process it via the channel.
	# The process will ensure that the action requested is a public method on the
	# channel declared by the user (so not one of the callbacks like #subscribed).
	def perform_action(data)
	action = extract_action(data)

	if processable_action?(action)
	payload = { channel_class: self.class.name, action: action, data: data }
	ActiveSupport::Notifications.instrument("perform_action.action_cable", payload) do
	dispatch_action(action, data)
	end
	else
	logger.error "Unable to process #{action_signature(action, data)}"
	end
	end

	test "accessing exceptions thrown during command execution" do
	run_in_eventmachine do
	setup_connection
	subscribe_to_chat_channel

	data = { "content" => "Hello World!", "action" => "throw_exception" }
	@subscriptions.execute_command "command" => "message", "identifier" => @chat_identifier, "data" => ActiveSupport::JSON.encode(data)

	exception = @connection.exceptions.first
	assert_kind_of ChatChannelError, exception
	end
	end

	def subscribe_to_channel
	run_callbacks :subscribe do
	subscribed
	end

	reject_subscription if subscription_rejected?
	ensure_confirmation_sent
	end