Matthias Andreas Benkard | 832a54e | 2019-01-29 09:27:38 +0100 | [diff] [blame] | 1 | /* |
| 2 | Copyright 2014 The Kubernetes Authors. |
| 3 | |
| 4 | Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | you may not use this file except in compliance with the License. |
| 6 | You may obtain a copy of the License at |
| 7 | |
| 8 | http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | |
| 10 | Unless required by applicable law or agreed to in writing, software |
| 11 | distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | See the License for the specific language governing permissions and |
| 14 | limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package wait |
| 18 | |
| 19 | import ( |
| 20 | "context" |
| 21 | "errors" |
| 22 | "math/rand" |
| 23 | "sync" |
| 24 | "time" |
| 25 | |
| 26 | "k8s.io/apimachinery/pkg/util/runtime" |
| 27 | ) |
| 28 | |
| 29 | // For any test of the style: |
| 30 | // ... |
| 31 | // <- time.After(timeout): |
| 32 | // t.Errorf("Timed out") |
| 33 | // The value for timeout should effectively be "forever." Obviously we don't want our tests to truly lock up forever, but 30s |
| 34 | // is long enough that it is effectively forever for the things that can slow down a run on a heavily contended machine |
| 35 | // (GC, seeks, etc), but not so long as to make a developer ctrl-c a test run if they do happen to break that test. |
| 36 | var ForeverTestTimeout = time.Second * 30 |
| 37 | |
| 38 | // NeverStop may be passed to Until to make it never stop. |
| 39 | var NeverStop <-chan struct{} = make(chan struct{}) |
| 40 | |
| 41 | // Group allows to start a group of goroutines and wait for their completion. |
| 42 | type Group struct { |
| 43 | wg sync.WaitGroup |
| 44 | } |
| 45 | |
| 46 | func (g *Group) Wait() { |
| 47 | g.wg.Wait() |
| 48 | } |
| 49 | |
| 50 | // StartWithChannel starts f in a new goroutine in the group. |
| 51 | // stopCh is passed to f as an argument. f should stop when stopCh is available. |
| 52 | func (g *Group) StartWithChannel(stopCh <-chan struct{}, f func(stopCh <-chan struct{})) { |
| 53 | g.Start(func() { |
| 54 | f(stopCh) |
| 55 | }) |
| 56 | } |
| 57 | |
| 58 | // StartWithContext starts f in a new goroutine in the group. |
| 59 | // ctx is passed to f as an argument. f should stop when ctx.Done() is available. |
| 60 | func (g *Group) StartWithContext(ctx context.Context, f func(context.Context)) { |
| 61 | g.Start(func() { |
| 62 | f(ctx) |
| 63 | }) |
| 64 | } |
| 65 | |
| 66 | // Start starts f in a new goroutine in the group. |
| 67 | func (g *Group) Start(f func()) { |
| 68 | g.wg.Add(1) |
| 69 | go func() { |
| 70 | defer g.wg.Done() |
| 71 | f() |
| 72 | }() |
| 73 | } |
| 74 | |
| 75 | // Forever calls f every period for ever. |
| 76 | // |
| 77 | // Forever is syntactic sugar on top of Until. |
| 78 | func Forever(f func(), period time.Duration) { |
| 79 | Until(f, period, NeverStop) |
| 80 | } |
| 81 | |
| 82 | // Until loops until stop channel is closed, running f every period. |
| 83 | // |
| 84 | // Until is syntactic sugar on top of JitterUntil with zero jitter factor and |
| 85 | // with sliding = true (which means the timer for period starts after the f |
| 86 | // completes). |
| 87 | func Until(f func(), period time.Duration, stopCh <-chan struct{}) { |
| 88 | JitterUntil(f, period, 0.0, true, stopCh) |
| 89 | } |
| 90 | |
| 91 | // NonSlidingUntil loops until stop channel is closed, running f every |
| 92 | // period. |
| 93 | // |
| 94 | // NonSlidingUntil is syntactic sugar on top of JitterUntil with zero jitter |
| 95 | // factor, with sliding = false (meaning the timer for period starts at the same |
| 96 | // time as the function starts). |
| 97 | func NonSlidingUntil(f func(), period time.Duration, stopCh <-chan struct{}) { |
| 98 | JitterUntil(f, period, 0.0, false, stopCh) |
| 99 | } |
| 100 | |
| 101 | // JitterUntil loops until stop channel is closed, running f every period. |
| 102 | // |
| 103 | // If jitterFactor is positive, the period is jittered before every run of f. |
| 104 | // If jitterFactor is not positive, the period is unchanged and not jittered. |
| 105 | // |
| 106 | // If sliding is true, the period is computed after f runs. If it is false then |
| 107 | // period includes the runtime for f. |
| 108 | // |
| 109 | // Close stopCh to stop. f may not be invoked if stop channel is already |
| 110 | // closed. Pass NeverStop to if you don't want it stop. |
| 111 | func JitterUntil(f func(), period time.Duration, jitterFactor float64, sliding bool, stopCh <-chan struct{}) { |
| 112 | var t *time.Timer |
| 113 | var sawTimeout bool |
| 114 | |
| 115 | for { |
| 116 | select { |
| 117 | case <-stopCh: |
| 118 | return |
| 119 | default: |
| 120 | } |
| 121 | |
| 122 | jitteredPeriod := period |
| 123 | if jitterFactor > 0.0 { |
| 124 | jitteredPeriod = Jitter(period, jitterFactor) |
| 125 | } |
| 126 | |
| 127 | if !sliding { |
| 128 | t = resetOrReuseTimer(t, jitteredPeriod, sawTimeout) |
| 129 | } |
| 130 | |
| 131 | func() { |
| 132 | defer runtime.HandleCrash() |
| 133 | f() |
| 134 | }() |
| 135 | |
| 136 | if sliding { |
| 137 | t = resetOrReuseTimer(t, jitteredPeriod, sawTimeout) |
| 138 | } |
| 139 | |
| 140 | // NOTE: b/c there is no priority selection in golang |
| 141 | // it is possible for this to race, meaning we could |
| 142 | // trigger t.C and stopCh, and t.C select falls through. |
| 143 | // In order to mitigate we re-check stopCh at the beginning |
| 144 | // of every loop to prevent extra executions of f(). |
| 145 | select { |
| 146 | case <-stopCh: |
| 147 | return |
| 148 | case <-t.C: |
| 149 | sawTimeout = true |
| 150 | } |
| 151 | } |
| 152 | } |
| 153 | |
| 154 | // Jitter returns a time.Duration between duration and duration + maxFactor * |
| 155 | // duration. |
| 156 | // |
| 157 | // This allows clients to avoid converging on periodic behavior. If maxFactor |
| 158 | // is 0.0, a suggested default value will be chosen. |
| 159 | func Jitter(duration time.Duration, maxFactor float64) time.Duration { |
| 160 | if maxFactor <= 0.0 { |
| 161 | maxFactor = 1.0 |
| 162 | } |
| 163 | wait := duration + time.Duration(rand.Float64()*maxFactor*float64(duration)) |
| 164 | return wait |
| 165 | } |
| 166 | |
| 167 | // ErrWaitTimeout is returned when the condition exited without success. |
| 168 | var ErrWaitTimeout = errors.New("timed out waiting for the condition") |
| 169 | |
| 170 | // ConditionFunc returns true if the condition is satisfied, or an error |
| 171 | // if the loop should be aborted. |
| 172 | type ConditionFunc func() (done bool, err error) |
| 173 | |
| 174 | // Backoff holds parameters applied to a Backoff function. |
| 175 | type Backoff struct { |
| 176 | Duration time.Duration // the base duration |
| 177 | Factor float64 // Duration is multiplied by factor each iteration |
| 178 | Jitter float64 // The amount of jitter applied each iteration |
| 179 | Steps int // Exit with error after this many steps |
| 180 | } |
| 181 | |
| 182 | // ExponentialBackoff repeats a condition check with exponential backoff. |
| 183 | // |
| 184 | // It checks the condition up to Steps times, increasing the wait by multiplying |
| 185 | // the previous duration by Factor. |
| 186 | // |
| 187 | // If Jitter is greater than zero, a random amount of each duration is added |
| 188 | // (between duration and duration*(1+jitter)). |
| 189 | // |
| 190 | // If the condition never returns true, ErrWaitTimeout is returned. All other |
| 191 | // errors terminate immediately. |
| 192 | func ExponentialBackoff(backoff Backoff, condition ConditionFunc) error { |
| 193 | duration := backoff.Duration |
| 194 | for i := 0; i < backoff.Steps; i++ { |
| 195 | if i != 0 { |
| 196 | adjusted := duration |
| 197 | if backoff.Jitter > 0.0 { |
| 198 | adjusted = Jitter(duration, backoff.Jitter) |
| 199 | } |
| 200 | time.Sleep(adjusted) |
| 201 | duration = time.Duration(float64(duration) * backoff.Factor) |
| 202 | } |
| 203 | if ok, err := condition(); err != nil || ok { |
| 204 | return err |
| 205 | } |
| 206 | } |
| 207 | return ErrWaitTimeout |
| 208 | } |
| 209 | |
| 210 | // Poll tries a condition func until it returns true, an error, or the timeout |
| 211 | // is reached. |
| 212 | // |
| 213 | // Poll always waits the interval before the run of 'condition'. |
| 214 | // 'condition' will always be invoked at least once. |
| 215 | // |
| 216 | // Some intervals may be missed if the condition takes too long or the time |
| 217 | // window is too short. |
| 218 | // |
| 219 | // If you want to Poll something forever, see PollInfinite. |
| 220 | func Poll(interval, timeout time.Duration, condition ConditionFunc) error { |
| 221 | return pollInternal(poller(interval, timeout), condition) |
| 222 | } |
| 223 | |
| 224 | func pollInternal(wait WaitFunc, condition ConditionFunc) error { |
| 225 | done := make(chan struct{}) |
| 226 | defer close(done) |
| 227 | return WaitFor(wait, condition, done) |
| 228 | } |
| 229 | |
| 230 | // PollImmediate tries a condition func until it returns true, an error, or the timeout |
| 231 | // is reached. |
| 232 | // |
| 233 | // Poll always checks 'condition' before waiting for the interval. 'condition' |
| 234 | // will always be invoked at least once. |
| 235 | // |
| 236 | // Some intervals may be missed if the condition takes too long or the time |
| 237 | // window is too short. |
| 238 | // |
| 239 | // If you want to Poll something forever, see PollInfinite. |
| 240 | func PollImmediate(interval, timeout time.Duration, condition ConditionFunc) error { |
| 241 | return pollImmediateInternal(poller(interval, timeout), condition) |
| 242 | } |
| 243 | |
| 244 | func pollImmediateInternal(wait WaitFunc, condition ConditionFunc) error { |
| 245 | done, err := condition() |
| 246 | if err != nil { |
| 247 | return err |
| 248 | } |
| 249 | if done { |
| 250 | return nil |
| 251 | } |
| 252 | return pollInternal(wait, condition) |
| 253 | } |
| 254 | |
| 255 | // PollInfinite tries a condition func until it returns true or an error |
| 256 | // |
| 257 | // PollInfinite always waits the interval before the run of 'condition'. |
| 258 | // |
| 259 | // Some intervals may be missed if the condition takes too long or the time |
| 260 | // window is too short. |
| 261 | func PollInfinite(interval time.Duration, condition ConditionFunc) error { |
| 262 | done := make(chan struct{}) |
| 263 | defer close(done) |
| 264 | return PollUntil(interval, condition, done) |
| 265 | } |
| 266 | |
| 267 | // PollImmediateInfinite tries a condition func until it returns true or an error |
| 268 | // |
| 269 | // PollImmediateInfinite runs the 'condition' before waiting for the interval. |
| 270 | // |
| 271 | // Some intervals may be missed if the condition takes too long or the time |
| 272 | // window is too short. |
| 273 | func PollImmediateInfinite(interval time.Duration, condition ConditionFunc) error { |
| 274 | done, err := condition() |
| 275 | if err != nil { |
| 276 | return err |
| 277 | } |
| 278 | if done { |
| 279 | return nil |
| 280 | } |
| 281 | return PollInfinite(interval, condition) |
| 282 | } |
| 283 | |
| 284 | // PollUntil tries a condition func until it returns true, an error or stopCh is |
| 285 | // closed. |
| 286 | // |
| 287 | // PollUntil always waits interval before the first run of 'condition'. |
| 288 | // 'condition' will always be invoked at least once. |
| 289 | func PollUntil(interval time.Duration, condition ConditionFunc, stopCh <-chan struct{}) error { |
| 290 | return WaitFor(poller(interval, 0), condition, stopCh) |
| 291 | } |
| 292 | |
| 293 | // PollImmediateUntil tries a condition func until it returns true, an error or stopCh is closed. |
| 294 | // |
| 295 | // PollImmediateUntil runs the 'condition' before waiting for the interval. |
| 296 | // 'condition' will always be invoked at least once. |
| 297 | func PollImmediateUntil(interval time.Duration, condition ConditionFunc, stopCh <-chan struct{}) error { |
| 298 | done, err := condition() |
| 299 | if err != nil { |
| 300 | return err |
| 301 | } |
| 302 | if done { |
| 303 | return nil |
| 304 | } |
| 305 | select { |
| 306 | case <-stopCh: |
| 307 | return ErrWaitTimeout |
| 308 | default: |
| 309 | return PollUntil(interval, condition, stopCh) |
| 310 | } |
| 311 | } |
| 312 | |
| 313 | // WaitFunc creates a channel that receives an item every time a test |
| 314 | // should be executed and is closed when the last test should be invoked. |
| 315 | type WaitFunc func(done <-chan struct{}) <-chan struct{} |
| 316 | |
| 317 | // WaitFor continually checks 'fn' as driven by 'wait'. |
| 318 | // |
| 319 | // WaitFor gets a channel from 'wait()'', and then invokes 'fn' once for every value |
| 320 | // placed on the channel and once more when the channel is closed. |
| 321 | // |
| 322 | // If 'fn' returns an error the loop ends and that error is returned, and if |
| 323 | // 'fn' returns true the loop ends and nil is returned. |
| 324 | // |
| 325 | // ErrWaitTimeout will be returned if the channel is closed without fn ever |
| 326 | // returning true. |
| 327 | func WaitFor(wait WaitFunc, fn ConditionFunc, done <-chan struct{}) error { |
| 328 | c := wait(done) |
| 329 | for { |
| 330 | _, open := <-c |
| 331 | ok, err := fn() |
| 332 | if err != nil { |
| 333 | return err |
| 334 | } |
| 335 | if ok { |
| 336 | return nil |
| 337 | } |
| 338 | if !open { |
| 339 | break |
| 340 | } |
| 341 | } |
| 342 | return ErrWaitTimeout |
| 343 | } |
| 344 | |
| 345 | // poller returns a WaitFunc that will send to the channel every interval until |
| 346 | // timeout has elapsed and then closes the channel. |
| 347 | // |
| 348 | // Over very short intervals you may receive no ticks before the channel is |
| 349 | // closed. A timeout of 0 is interpreted as an infinity. |
| 350 | // |
| 351 | // Output ticks are not buffered. If the channel is not ready to receive an |
| 352 | // item, the tick is skipped. |
| 353 | func poller(interval, timeout time.Duration) WaitFunc { |
| 354 | return WaitFunc(func(done <-chan struct{}) <-chan struct{} { |
| 355 | ch := make(chan struct{}) |
| 356 | |
| 357 | go func() { |
| 358 | defer close(ch) |
| 359 | |
| 360 | tick := time.NewTicker(interval) |
| 361 | defer tick.Stop() |
| 362 | |
| 363 | var after <-chan time.Time |
| 364 | if timeout != 0 { |
| 365 | // time.After is more convenient, but it |
| 366 | // potentially leaves timers around much longer |
| 367 | // than necessary if we exit early. |
| 368 | timer := time.NewTimer(timeout) |
| 369 | after = timer.C |
| 370 | defer timer.Stop() |
| 371 | } |
| 372 | |
| 373 | for { |
| 374 | select { |
| 375 | case <-tick.C: |
| 376 | // If the consumer isn't ready for this signal drop it and |
| 377 | // check the other channels. |
| 378 | select { |
| 379 | case ch <- struct{}{}: |
| 380 | default: |
| 381 | } |
| 382 | case <-after: |
| 383 | return |
| 384 | case <-done: |
| 385 | return |
| 386 | } |
| 387 | } |
| 388 | }() |
| 389 | |
| 390 | return ch |
| 391 | }) |
| 392 | } |
| 393 | |
| 394 | // resetOrReuseTimer avoids allocating a new timer if one is already in use. |
| 395 | // Not safe for multiple threads. |
| 396 | func resetOrReuseTimer(t *time.Timer, d time.Duration, sawTimeout bool) *time.Timer { |
| 397 | if t == nil { |
| 398 | return time.NewTimer(d) |
| 399 | } |
| 400 | if !t.Stop() && !sawTimeout { |
| 401 | <-t.C |
| 402 | } |
| 403 | t.Reset(d) |
| 404 | return t |
| 405 | } |