Timeout Stability Pattern

1. Code

allows a process to stop waiting for an answer once it's clear that an answer may not be coming
3 components:
- client : calls a slow function
- slowfunction : a long running function
- timeout : wrapper over slow function
straightforward if a function utilizes context.Context in golang,

1. Code

ctx := context.Background()
ctxt,cancel := context.WithTimeout(ctx, 10*time.Second)
defer cancel()
result, err := SomeFunction(ctxt)

This isn't usually the case though
- build a closure that respects the context in such a case, followed by a select over your injected timeout context and the result of a goroutined slow function
will need to convert the slow function into a context respecting wrapper as follows

type SlowFunction func(string) (string, error)

type WithContext func(context.Context, string) (string, error)

func Timeout(f SlowFunction) WithContext {
        return func(ctx context.Context, arg string) (string error) {
                chres := make(chan string) //channel for results
                cherr := make(chan string) //channel for errors

                go func() {
                        res, err := f(arg) //dispatch slow function
                        chres <- res
                        cherr <- err
                }()

                select {
                case res := <-chres://if done before timeout
                        return res, <-cherr
                case <-ctx.Done()://in case of timeout
                        return "",ctx.Err()
                }
        }
}

finally, using Timeout will be like

func main() {
        ctx := context.Background()
        ctxt, cancel := context.WithTimeout(ctx, 1*time.Second)
        defer cancel()

        timeout := Timeout(Slow)
        res, err := timeout(ctxt, "some input")

        fmt.Println(res, err)
}

an alternative to using context.Context (context.Context is the preferred method btw), is using the time.After function : https://pkg.go.dev/time#After

Timeout Stability Pattern

Table of Contents

1. Code