open-consul/testutil/retry/retry.go

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// Package retry provides support for repeating operations in tests.
//
// A sample retry operation looks like this:
//
// func TestX(t *testing.T) {
// retry.Run(t, func(r *retry.R) {
// if err := foo(); err != nil {
// r.Fatal("f: ", err)
// }
// })
// }
//
package retry
import (
"bytes"
"fmt"
"runtime"
"strings"
"sync"
"time"
)
// Failer is an interface compatible with testing.T.
type Failer interface {
// Log is called for the final test output
Log(args ...interface{})
// FailNow is called when the retrying is abandoned.
FailNow()
}
// R provides context for the retryer.
type R struct {
fail bool
output []string
}
func (r *R) FailNow() {
r.fail = true
runtime.Goexit()
}
func (r *R) Fatal(args ...interface{}) {
r.log(fmt.Sprint(args...))
r.FailNow()
}
func (r *R) Fatalf(format string, args ...interface{}) {
r.log(fmt.Sprintf(format, args...))
r.FailNow()
}
func (r *R) Error(args ...interface{}) {
r.log(fmt.Sprint(args...))
r.fail = true
}
func (r *R) log(s string) {
r.output = append(r.output, decorate(s))
}
func decorate(s string) string {
_, file, line, ok := runtime.Caller(3)
if ok {
n := strings.LastIndex(file, "/")
if n >= 0 {
file = file[n+1:]
}
} else {
file = "???"
line = 1
}
return fmt.Sprintf("%s:%d: %s", file, line, s)
}
func Run(t Failer, f func(r *R)) {
run(OneSec(), t, f)
}
func RunWith(r Retryer, t Failer, f func(r *R)) {
run(r, t, f)
}
func dedup(a []string) string {
if len(a) == 0 {
return ""
}
m := map[string]int{}
for _, s := range a {
m[s] = m[s] + 1
}
var b bytes.Buffer
for _, s := range a {
if _, ok := m[s]; ok {
b.WriteString(s)
b.WriteRune('\n')
delete(m, s)
}
}
return string(b.Bytes())
}
func run(r Retryer, t Failer, f func(r *R)) {
rr := &R{}
fail := func() {
out := dedup(rr.output)
if out != "" {
t.Log(out)
}
t.FailNow()
}
for r.NextOr(fail) {
var wg sync.WaitGroup
wg.Add(1)
go func() {
defer wg.Done()
f(rr)
}()
wg.Wait()
if rr.fail {
rr.fail = false
continue
}
break
}
}
// OneSec repeats an operation for one second and waits 25ms in between.
func OneSec() *Timer {
return &Timer{Timeout: time.Second, Wait: 25 * time.Millisecond}
}
// ThreeTimes repeats an operation three times and waits 25ms in between.
func ThreeTimes() *Counter {
return &Counter{Count: 3, Wait: 25 * time.Millisecond}
}
// Retryer provides an interface for repeating operations
// until they succeed or an exit condition is met.
type Retryer interface {
// NextOr returns true if the operation should be repeated.
// Otherwise, it calls fail and returns false.
NextOr(fail func()) bool
}
// Counter repeats an operation a given number of
// times and waits between subsequent operations.
type Counter struct {
Count int
Wait time.Duration
count int
}
func (r *Counter) NextOr(fail func()) bool {
if r.count == r.Count {
fail()
return false
}
if r.count > 0 {
time.Sleep(r.Wait)
}
r.count++
return true
}
// Timer repeats an operation for a given amount
// of time and waits between subsequent operations.
type Timer struct {
Timeout time.Duration
Wait time.Duration
// stop is the timeout deadline.
// Set on the first invocation of Next().
stop time.Time
}
func (r *Timer) NextOr(fail func()) bool {
if r.stop.IsZero() {
r.stop = time.Now().Add(r.Timeout)
return true
}
if time.Now().After(r.stop) {
fail()
return false
}
time.Sleep(r.Wait)
return true
}