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policy.go
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policy.go
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// Copyright (c) 2019 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package quotas
import (
"sync"
)
// MultiStageRateLimiter indicates a domain specific rate limit policy
type MultiStageRateLimiter struct {
sync.RWMutex
rps RPSFunc
domainRPS RPSKeyFunc
domainLimiters map[string]*DynamicRateLimiter
globalLimiter *DynamicRateLimiter
}
// NewMultiStageRateLimiter returns a new domain quota rate limiter. This is about
// an order of magnitude slower than
func NewMultiStageRateLimiter(rps RPSFunc, domainRps RPSKeyFunc) *MultiStageRateLimiter {
rl := &MultiStageRateLimiter{
rps: rps,
domainRPS: domainRps,
domainLimiters: map[string]*DynamicRateLimiter{},
globalLimiter: NewDynamicRateLimiter(rps),
}
return rl
}
// Allow attempts to allow a request to go through. The method returns
// immediately with a true or false indicating if the request can make
// progress
func (d *MultiStageRateLimiter) Allow(info Info) bool {
domain := info.Domain
if len(domain) == 0 {
return d.globalLimiter.Allow()
}
// check if we have a per-domain limiter - if not create a default one for
// the domain.
d.RLock()
limiter, ok := d.domainLimiters[domain]
d.RUnlock()
if !ok {
// create a new limiter
domainLimiter := NewDynamicRateLimiter(
func() float64 {
return d.domainRPS(domain)
},
)
// verify that it is needed and add to map
d.Lock()
limiter, ok = d.domainLimiters[domain]
if !ok {
d.domainLimiters[domain] = domainLimiter
limiter = domainLimiter
}
d.Unlock()
}
// take a reservation with the domain limiter first
rsv := limiter.Reserve()
if !rsv.OK() {
return false
}
// ensure that the reservation does not break the global rate limit, if it
// does, cancel the reservation and do not allow to proceed.
if !d.globalLimiter.Allow() {
rsv.Cancel()
return false
}
return true
}