diff --git a/ratelimit/token_bucket.go b/ratelimit/token_bucket.go index f6df9d0..7bc06b2 100644 --- a/ratelimit/token_bucket.go +++ b/ratelimit/token_bucket.go @@ -18,9 +18,37 @@ // limiter based on a token-bucket algorithm. Requests that would exceed the // maximum request rate are simply rejected with an error. func NewTokenBucketLimiter(tb *ratelimit.Bucket) endpoint.Middleware { + return NewErroringLimiter(NewAllower(tb)) +} + +// 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 NewDelayingLimiter(NewWaiter(tb)) return func(next endpoint.Endpoint) endpoint.Endpoint { return func(ctx context.Context, request interface{}) (interface{}, error) { - if tb.TakeAvailable(1) == 0 { + sleep(tb.Take(1)) + return next(ctx, request) + } + } +} + +// Allower dictates whether or not a request is acceptable to run. +// The Limiter from "golang.org/x/time/rate" already implements this interface, +// one is able to use that in NewErroringLimiter without any modifications. +type Allower interface { + Allow() bool +} + +// NewErroringLimiter returns an endpoint.Middleware that acts as a rate +// limiter. Requests that would exceed the +// maximum request rate are simply rejected with an error. +func NewErroringLimiter(limit Allower) endpoint.Middleware { + return func(next endpoint.Endpoint) endpoint.Endpoint { + return func(ctx context.Context, request interface{}) (interface{}, error) { + if !limit.Allow() { return nil, ErrLimited } return next(ctx, request) @@ -28,15 +56,62 @@ } } -// 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 { +// Waiter dictates how long a request must be delayed. +// The Limiter from "golang.org/x/time/rate" already implements this interface, +// one is able to use that in NewDelayingLimiter without any modifications. +type Waiter interface { + Wait(ctx context.Context) error +} + +// NewDelayingLimiter returns an endpoint.Middleware that acts as a +// request throttler. Requests that would +// exceed the maximum request rate are delayed via the Waiter function +func NewDelayingLimiter(limit Waiter) endpoint.Middleware { return func(next endpoint.Endpoint) endpoint.Endpoint { return func(ctx context.Context, request interface{}) (interface{}, error) { - sleep(tb.Take(1)) + if err := limit.Wait(ctx); err != nil { + return nil, err + } return next(ctx, request) } } } + +// AllowerFunc is an adapter that lets a function operate as if +// it implements Allower +type AllowerFunc func() bool + +// Allow makes the adapter implement Allower +func (f AllowerFunc) Allow() bool { + return f() +} + +// NewAllower turns an existing ratelimit.Bucket into an API-compatible form +func NewAllower(tb *ratelimit.Bucket) Allower { + return AllowerFunc(func() bool { + return (tb.TakeAvailable(1) != 0) + }) +} + +// WaiterFunc is an adapter that lets a function operate as if +// it implements Waiter +type WaiterFunc func(ctx context.Context) error + +// Wait makes the adapter implement Waiter +func (f WaiterFunc) Wait(ctx context.Context) error { + return f(ctx) +} + +// NewWaiter turns an existing ratelimit.Bucket into an API-compatible form +func NewWaiter(tb *ratelimit.Bucket) Waiter { + return WaiterFunc(func(ctx context.Context) error { + dur := tb.Take(1) + select { + case <-ctx.Done(): + return ctx.Err() + case <-time.After(dur): + // happy path + } + return nil + }) +} diff --git a/ratelimit/token_bucket_test.go b/ratelimit/token_bucket_test.go index 54225b8..319f845 100644 --- a/ratelimit/token_bucket_test.go +++ b/ratelimit/token_bucket_test.go @@ -3,6 +3,7 @@ import ( "context" "math" + "strings" "testing" "time" @@ -10,6 +11,7 @@ "github.com/go-kit/kit/endpoint" "github.com/go-kit/kit/ratelimit" + "golang.org/x/time/rate" ) func TestTokenBucketLimiter(t *testing.T) { @@ -53,3 +55,29 @@ t.Errorf("rate=%d: want %v, have %v", rate, ratelimit.ErrLimited, err) } } + +func TestXRateErroring(t *testing.T) { + limit := rate.NewLimiter(rate.Every(time.Minute), 1) + e := func(context.Context, interface{}) (interface{}, error) { return struct{}{}, nil } + testLimiter(t, ratelimit.NewErroringLimiter(limit)(e), 1) +} + +func TestXRateDelaying(t *testing.T) { + limit := rate.NewLimiter(rate.Every(time.Minute), 1) + e := func(context.Context, interface{}) (interface{}, error) { return struct{}{}, nil } + e = ratelimit.NewDelayingLimiter(limit)(e) + + _, err := e(context.Background(), struct{}{}) + if err != nil { + t.Errorf("unexpected: %v\n", err) + } + + dur := 500 * time.Millisecond + ctx, cxl := context.WithTimeout(context.Background(), dur) + defer cxl() + + _, err = e(ctx, struct{}{}) + if !strings.Contains(err.Error(), "exceed context deadline") { + t.Errorf("expected timeout: %v\n", err) + } +}