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caply.go
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caply.go
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package caply
import (
"fmt"
"github.com/pkg/errors"
"time"
)
// NewCaply returns new instance of Caply
func NewCaply(maxOps int, perPeriod time.Duration, store Store) (*Caply, error) {
if perPeriod < 1*time.Second || perPeriod > 1*time.Hour {
return nil, errors.New("perPeriod has to be between 1 second and 1 hour")
}
return &Caply{
store,
maxOps,
perPeriod,
}, nil
}
// Caply is fixed window rate limiter where every next request is placed into respective time window batch
type Caply struct {
store Store
maxRequests int
perPeriod time.Duration
}
// Exceeded finds specified operation in current time window and returns true if limit has already exceeded (false otherwise)
func (rt *Caply) Exceeded(opName string) (bool, error) {
bucketTimeStamp := 0
now := time.Now()
if rt.perPeriod < 1*time.Minute {
bucketTimeStamp = now.Minute()
} else if rt.perPeriod < 1*time.Hour {
bucketTimeStamp = now.Hour()
}
key := fmt.Sprintf("%s_%d", opName, bucketTimeStamp)
val, err := rt.store.Get(key)
if err != nil {
return false, errors.Wrapf(err, "failed to get current limit state for key %s", key)
}
if val >= rt.maxRequests {
return true, nil
} else {
err = rt.store.AddOne(key, rt.perPeriod)
if err != nil {
return false, errors.Wrapf(err, "failed to increase rate limit for key %s", key)
}
}
return false, nil
}