/usr/share/gocode/src/github.com/jacobsa/ratelimit/throttle.go is in golang-github-jacobsa-ratelimit-dev 0.0~git20150723.0.2ca5e0c-2.
This file is owned by root:root, with mode 0o644.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 | // Copyright 2015 Google Inc. All Rights Reserved.
//
// 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 ratelimit
import (
"time"
"github.com/jacobsa/syncutil"
"golang.org/x/net/context"
)
// A simple interface for limiting the rate of some event. Unlike TokenBucket,
// does not allow the user control over what time means.
//
// Safe for concurrent access.
type Throttle interface {
// Return the maximum number of tokens that can be requested in a call to
// Wait.
Capacity() (c uint64)
// Acquire the given number of tokens from the underlying token bucket, then
// sleep until when it says to wake. If the context is cancelled before then,
// return early with an error.
//
// REQUIRES: tokens <= capacity
Wait(ctx context.Context, tokens uint64) (err error)
}
// Create a throttle that uses time.Now to judge the time given to the
// underlying token bucket.
//
// Be aware of the monotonicity issues. In particular:
//
// * If the system clock jumps into the future, the throttle will let through
// a burst of traffic.
//
// * If the system clock jumps into the past, it will halt all traffic for
// a potentially very long amount of time.
//
func NewThrottle(
rateHz float64,
capacity uint64) (t Throttle) {
typed := &throttle{
startTime: time.Now(),
bucket: NewTokenBucket(rateHz, capacity),
}
typed.mu = syncutil.NewInvariantMutex(typed.checkInvariants)
t = typed
return
}
type throttle struct {
/////////////////////////
// Constant data
/////////////////////////
startTime time.Time
/////////////////////////
// Mutable state
/////////////////////////
mu syncutil.InvariantMutex
// INVARIANT: bucket.CheckInvariants()
//
// GUARDED_BY(mu)
bucket TokenBucket
}
// LOCKS_REQUIRED(t.mu)
func (t *throttle) checkInvariants() {
// INVARIANT: bucket.CheckInvariants()
t.bucket.CheckInvariants()
}
// LOCKS_EXCLUDED(t.mu)
func (t *throttle) Capacity() (c uint64) {
t.mu.Lock()
c = t.bucket.Capacity()
t.mu.Unlock()
return
}
// LOCKS_EXCLUDED(t.mu)
func (t *throttle) Wait(
ctx context.Context,
tokens uint64) (err error) {
now := MonotonicTime(time.Now().Sub(t.startTime))
t.mu.Lock()
sleepUntil := t.bucket.Remove(now, tokens)
t.mu.Unlock()
select {
case <-ctx.Done():
err = ctx.Err()
return
case <-time.After(time.Duration(sleepUntil - now)):
return
}
}
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