Add generics to subscriber and publisher and fix potential deadlock #602
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,76 +1,74 @@ | ||
| package models | ||
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| import ( | ||
| "fmt" | ||
| "sync" | ||
| ) | ||
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| type Publisher[T any] struct { | ||
| mux sync.RWMutex | ||
| subscribers map[Subscriber[T]]struct{} | ||
| } | ||
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| func NewPublisher[T any]() *Publisher[T] { | ||
| return &Publisher[T]{ | ||
| mux: sync.RWMutex{}, | ||
| subscribers: make(map[Subscriber[T]]struct{}), | ||
| } | ||
| } | ||
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| func (p *Publisher[T]) Publish(data T) { | ||
| p.mux.RLock() | ||
| defer p.mux.RUnlock() | ||
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| for s := range p.subscribers { | ||
| s.Notify(data) | ||
| } | ||
| } | ||
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| func (p *Publisher[T]) Subscribe(s Subscriber[T]) { | ||
| p.mux.Lock() | ||
| defer p.mux.Unlock() | ||
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| p.subscribers[s] = struct{}{} | ||
| } | ||
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| func (p *Publisher[T]) Unsubscribe(s Subscriber[T]) { | ||
| p.mux.Lock() | ||
| defer p.mux.Unlock() | ||
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| delete(p.subscribers, s) | ||
| } | ||
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| type Subscriber[T any] interface { | ||
| Notify(data T) | ||
| Error() <-chan error | ||
| } | ||
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| type Subscription[T any] struct { | ||
| err chan error | ||
| callback func(data T) error | ||
| } | ||
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| func NewSubscription[T any](callback func(T) error) *Subscription[T] { | ||
| return &Subscription[T]{ | ||
| callback: callback, | ||
| err: make(chan error), | ||
| } | ||
| } | ||
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| func (b *Subscription[T]) Notify(data T) { | ||
| err := b.callback(data) | ||
| if err != nil { | ||
| select { | ||
| case b.err <- err: | ||
|
There was a problem hiding this comment. I wonder if the subscription cares about callback returning error or not. I think the subscription's responsibility is to deliver the data to the callback. If there is error, it's the callback's job to handle it, log it, or even crash. The callback has all the context of why this would error, so it's better being handled there. There was a problem hiding this comment. Agreed! |
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| default: | ||
| // TODO: handle this better! | ||
| panic(fmt.Sprintf("failed to send error to subscription %v", err)) | ||
| } | ||
| } | ||
| } | ||
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| func (b *Subscription[T]) Error() <-chan error { | ||
| return b.err | ||
| } | ||
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I am a bit hesitant about removing this assignment here. If I remember correctly, this was added by Gregor, due to some issue with the event streaming API. But on the other hand, the CI is passing, so maybe it's not needed after all 🤷♂️
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Thanks for the heads up, I'll take a look at the history, maybe there were some clues what specific problem this was solving.
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If you don't find anything, we can just merge it. It doesn't seem to break anything, and the E2E tests do exercise this part.
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@janezpodhostnik I did investigate this. What I found is:
has the format:
0x8b841deff1dbca0881c995ad77574d17.I think Gregor changed it to
uuid, to match the format of the event streaming API,e.g.:
69a20431-f601-43da-99f1-aa4bfd4d1bacBut we're using entirely the subscription functionality from
Geth, so there's no need to go with theuuidformat.I think we're all good here. It would make sense though, to log the proper
subscription-id, e.g.There was a problem hiding this comment.
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addressed in 47ecbea. Please check if that is what you had in mind.
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Nice, good idea adding both 👍