/
ratelimiter.go
67 lines (57 loc) · 1.89 KB
/
ratelimiter.go
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// Copyright 2021 Ahmet Alp Balkan
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package ratelimiter
import (
"context"
"fmt"
"time"
"github.com/go-redis/redis/v8"
"go.opentelemetry.io/otel/trace"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/status"
)
type TimeProvider func() time.Time
type RateLimiter interface {
Hit(ctx context.Context, id string, max int64) error
}
type rateLimiter struct {
R *redis.Client
Trace trace.Tracer
T TimeProvider
Window time.Duration
}
func New(r *redis.Client, t TimeProvider, trace trace.Tracer, windowSize time.Duration) RateLimiter {
return &rateLimiter{R: r, T: t, Trace: trace, Window: windowSize}
}
func (r *rateLimiter) Hit(ctx context.Context, key string, max int64) error {
ctx, s := r.Trace.Start(ctx, "rate limiter")
defer s.End()
bucket := r.T().Truncate(r.Window)
k := RateKey(key, bucket)
p := r.R.TxPipeline()
incr := p.Incr(ctx, k)
p.Expire(ctx, k, r.Window*2) // no need for *2 here, but keep it for debugging
_, err := p.Exec(ctx)
if err != nil {
return status.Error(codes.Internal, fmt.Sprintf("failed to reach redis: %v", err))
}
cur := incr.Val()
if cur > max {
return status.Error(codes.ResourceExhausted, fmt.Sprintf("rate limited: %d requests in the past %v (max: %d)", cur, r.Window, max))
}
return nil
}
func RateKey(id string, t time.Time) string {
return fmt.Sprintf("rate::%s::%d", id, t.Unix())
}