// NewTokenBucketThrottler returns an endpoint.Middleware that acts as a
// request throttler based on a token-bucket algorithm. Requests that would
// exceed the maximum request rate are delayed via the parameterized sleep
// function. By default you may pass time.Sleep.
func NewTokenBucketThrottler(tb *ratelimit.Bucket, sleep func(time.Duration)) endpoint.Middleware {
return func(next endpoint.Endpoint) endpoint.Endpoint {
return func() error {
sleep(tb.Take(1))
return next()
}
}
}
// NewTokenBucketThrottler returns an endpoint.Middleware that acts as a
// request throttler based on a token-bucket algorithm. Requests that would
// exceed the maximum request rate are delayed via the parameterized sleep
// function. By default you may pass time.Sleep.
func NewTokenBucketThrottler(tb *ratelimit.Bucket, sleep func(time.Duration)) endpoint.Middleware {
return func(next endpoint.Endpoint) endpoint.Endpoint {
return func(ctx context.Context, request interface{}) (interface{}, error) {
sleep(tb.Take(1))
return next(ctx, request)
}
}
}
func limit(b *ratelimit.Bucket, wait bool, errId string) func() error {
return func() error {
if wait {
time.Sleep(b.Take(1))
} else if b.TakeAvailable(1) == 0 {
return errors.New(errId, "too many request", 429)
}
return nil
}
}
func makeRateLimitFunc(sessionRateLimit, globalRateLimit *ratelimit.Bucket) func(int64) {
// This may be a case of super duper premature optimization... We build an
// optimized function to do the rate limiting here based on what we need
// to do and then use it in the loop.
if sessionRateLimit == nil && globalRateLimit == nil {
// No limiting needed. We could equally well return a func(int64){} and
// not do a nil check were we use it, but I think the nil check there
// makes it clear that there will be no limiting if none is
// configured...
return nil
}
if sessionRateLimit == nil {
// We only have a global limiter
return func(bytes int64) {
globalRateLimit.Wait(bytes)
}
}
if globalRateLimit == nil {
// We only have a session limiter
return func(bytes int64) {
sessionRateLimit.Wait(bytes)
}
}
// We have both. Queue the bytes on both the global and session specific
// rate limiters. Wait for both in parallell, so that the actual send
// happens when both conditions are satisfied. In practice this just means
// wait the longer of the two times.
return func(bytes int64) {
t0 := sessionRateLimit.Take(bytes)
t1 := globalRateLimit.Take(bytes)
if t0 > t1 {
time.Sleep(t0)
} else {
time.Sleep(t1)
}
}
}