ActionCable messaging doesn't recover from disconnect/reconnect

I was super excited to finally be able to use ActionCable for a new project (late to the party!) but was a little bewildered that guaranteed message delivery (and delivery ordering) wasn’t baked in. Messages are not delivered unless a client is connected at the time the message is broadcast, even if they reconnect shortly afterward.

I know this would make ActionCable heavier (it’d need to hold on to messages longer, and also keep track of delivery status for each subscribed user) but I think this would be a good feature to add.

https://logux.io has already solved most of the details around this, but they’re trying to solve a much deeper problem there (concurrent editing). Their strategies for message recovery look good though.

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If you require a reliable channel with automatic recovery have a look at GitHub - discourse/message_bus: A reliable and robust messaging bus for Ruby and Rack this is what we have used for the last 7 years at Discourse. It has both a redis and pg implementation.

I think a great outcome would be for the message_bus gem to ship a “back-end / front-end adapter” for ActionCable, that way you could just install the gem to get reliable messaging for free. If anyone wants to work on this … let me know.

Over the years Rails has been very open to … opening up the menu so I am sure if someone was keen to take on such a project the team would be open.

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I’m excited that @julianrubisch has a functioning alpha implementation of StimulusReflex - and by extension, ActionCable - working with message_bus in this PR.

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@samsaffron, in all my searching I never came across message_bus! Possibly because I was looking for alternative web socket solutions. I’ll definitely take a look at it though :slight_smile:

Is there a reason message_bus doesn’t use web sockets as a transportation option?

@leastbad, Interesting to see that PR. I’ll keep an eye on it.

@Spike message_bus is explicitly an alternative to websockets.

Sam has written his wisdom extensively here.

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Thanks @leastbad, I’ll have a read :smiley: