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tailscale/tstime/rate/rate_test.go

251 lines
5.4 KiB
Go

// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// This is a modified, simplified version of code from golang.org/x/time/rate.
// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build go1.7
// +build go1.7
package rate
import (
"context"
"math"
"runtime"
"sync"
"sync/atomic"
"testing"
"time"
"tailscale.com/tstime/mono"
)
func closeEnough(a, b Limit) bool {
return (math.Abs(float64(a)/float64(b)) - 1.0) < 1e-9
}
func TestEvery(t *testing.T) {
cases := []struct {
interval time.Duration
lim Limit
}{
{1 * time.Nanosecond, Limit(1e9)},
{1 * time.Microsecond, Limit(1e6)},
{1 * time.Millisecond, Limit(1e3)},
{10 * time.Millisecond, Limit(100)},
{100 * time.Millisecond, Limit(10)},
{1 * time.Second, Limit(1)},
{2 * time.Second, Limit(0.5)},
{time.Duration(2.5 * float64(time.Second)), Limit(0.4)},
{4 * time.Second, Limit(0.25)},
{10 * time.Second, Limit(0.1)},
{time.Duration(math.MaxInt64), Limit(1e9 / float64(math.MaxInt64))},
}
for _, tc := range cases {
lim := Every(tc.interval)
if !closeEnough(lim, tc.lim) {
t.Errorf("Every(%v) = %v want %v", tc.interval, lim, tc.lim)
}
}
}
const (
d = 100 * time.Millisecond
)
var (
t0 = mono.Now()
t1 = t0.Add(time.Duration(1) * d)
t2 = t0.Add(time.Duration(2) * d)
t3 = t0.Add(time.Duration(3) * d)
t4 = t0.Add(time.Duration(4) * d)
t5 = t0.Add(time.Duration(5) * d)
t9 = t0.Add(time.Duration(9) * d)
)
type allow struct {
t mono.Time
ok bool
}
func run(t *testing.T, lim *Limiter, allows []allow) {
t.Helper()
for i, allow := range allows {
ok := lim.allow(allow.t)
if ok != allow.ok {
t.Errorf("step %d: lim.AllowN(%v) = %v want %v",
i, allow.t, ok, allow.ok)
}
}
}
func TestLimiterBurst1(t *testing.T) {
run(t, NewLimiter(10, 1), []allow{
{t0, true},
{t0, false},
{t0, false},
{t1, true},
{t1, false},
{t1, false},
{t2, true},
{t2, false},
})
}
func TestLimiterJumpBackwards(t *testing.T) {
run(t, NewLimiter(10, 3), []allow{
{t1, true}, // start at t1
{t0, true}, // jump back to t0, two tokens remain
{t0, true},
{t0, false},
{t0, false},
{t1, true}, // got a token
{t1, false},
{t1, false},
{t2, true}, // got another token
{t2, false},
{t2, false},
})
}
// Ensure that tokensFromDuration doesn't produce
// rounding errors by truncating nanoseconds.
// See golang.org/issues/34861.
func TestLimiter_noTruncationErrors(t *testing.T) {
if !NewLimiter(0.7692307692307693, 1).Allow() {
t.Fatal("expected true")
}
}
func TestSimultaneousRequests(t *testing.T) {
const (
limit = 1
burst = 5
numRequests = 15
)
var (
wg sync.WaitGroup
numOK = uint32(0)
)
// Very slow replenishing bucket.
lim := NewLimiter(limit, burst)
// Tries to take a token, atomically updates the counter and decreases the wait
// group counter.
f := func() {
defer wg.Done()
if ok := lim.Allow(); ok {
atomic.AddUint32(&numOK, 1)
}
}
wg.Add(numRequests)
for i := 0; i < numRequests; i++ {
go f()
}
wg.Wait()
if numOK != burst {
t.Errorf("numOK = %d, want %d", numOK, burst)
}
}
func TestLongRunningQPS(t *testing.T) {
if testing.Short() {
t.Skip("skipping in short mode")
}
if runtime.GOOS == "openbsd" {
t.Skip("low resolution time.Sleep invalidates test (golang.org/issue/14183)")
return
}
// The test runs for a few seconds executing many requests and then checks
// that overall number of requests is reasonable.
const (
limit = 100
burst = 100
)
var numOK = int32(0)
lim := NewLimiter(limit, burst)
var wg sync.WaitGroup
f := func() {
if ok := lim.Allow(); ok {
atomic.AddInt32(&numOK, 1)
}
wg.Done()
}
// This will still offer ~500 requests per second,
// but won't consume outrageous amount of CPU.
start := time.Now()
end := start.Add(1 * time.Second)
ticker := time.NewTicker(2 * time.Millisecond)
defer ticker.Stop()
for now := range ticker.C {
if now.After(end) {
break
}
wg.Add(1)
go f()
}
wg.Wait()
elapsed := time.Since(start)
ideal := burst + (limit * float64(elapsed) / float64(time.Second))
// We should never get more requests than allowed.
if want := int32(ideal + 1); numOK > want {
t.Errorf("numOK = %d, want %d (ideal %f)", numOK, want, ideal)
}
// We should get close-ish to the number of requests allowed.
// Trying to get too close causes flakes. Treat this as a sanity check.
if want := int32(0.9 * ideal); numOK < want {
t.Errorf("numOK = %d, want %d (ideal %f)", numOK, want, ideal)
}
}
type request struct {
t time.Time
n int
act time.Time
ok bool
}
// dFromDuration converts a duration to a multiple of the global constant d
func dFromDuration(dur time.Duration) int {
// Adding a millisecond to be swallowed by the integer division
// because we don't care about small inaccuracies
return int((dur + time.Millisecond) / d)
}
// dSince returns multiples of d since t0
func dSince(t mono.Time) int {
return dFromDuration(t.Sub(t0))
}
type wait struct {
name string
ctx context.Context
n int
delay int // in multiples of d
nilErr bool
}
func BenchmarkAllowN(b *testing.B) {
lim := NewLimiter(Every(1*time.Second), 1)
now := mono.Now()
b.ReportAllocs()
b.ResetTimer()
b.RunParallel(func(pb *testing.PB) {
for pb.Next() {
lim.allow(now)
}
})
}