[ANN] Exponential Backoff Algorithm

[Cenk Altı]

https://github.com/cenkalti/backoff

I have ported the exponential backoff algorithm from google-http-java-client with tests. Then replaced integer types with appropriate types from time package.

Also included a helper for retrying operation that may fail:

    operation := func() error {

        // An operation that migth fail

    }

    err := backoff.Retry(operation, NewExponentialBackoff())

    if err != nil {

        // handle error

    }

    // operation is successfull

1. The original code was under Apache 2 license but I have released it under MIT license. I don't know if it counts as a derivative work or completely new software. How should I license it?

2. Any suggestions on the API?

Original implementation: https://code.google.com/p/google-http-java-client/source/browse/google-http-client/src/main/java/com/google/api/client/util/ExponentialBackOff.java

Go implementation: https://github.com/cenkalti/backoff/blob/master/exponential.go

3. If you want to contribute you can implement a http.RoundTripper for retrying HTTP requests and send a pull request. I will be happy to accept. Or, you can add different back-off algorithms (LinearBackoff, vs.).

[Dmitry Vyukov]

I don't like inversion of control, especially for simple/helper
things. For backoff I usually do something along the lines of:

for b := backoff.Exponential{}; b.Backoff(); {
whatever you want goes here
}

However, in the context of reusable Go API I would also consider
channels, because they can be involved in selects, eg:

var b backoff.Exponential
...
select {
case <-b.Backoff():
continue
case <-foo:
...
case <-bar:
...

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[Ingo Oeser]

Great patterns.

I was playing around with naive exponential backoff while prototyping retry helpers at http://godoc.org/github.com/nightlyone/reconnect

around an Reconnectable interface like http://play.golang.org/p/Sx87ug9BrM 

The idea is to use this reconnecting in requests or reconnect in the background to replenish a pool of connections.