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Move backoff logic into own struct and increase test coverage of timeout logic #3031
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| Original file line number | Diff line number | Diff line change |
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| /* | ||
| Copyright 2020 The Tekton Authors | ||
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| 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 | ||
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| http://www.apache.org/licenses/LICENSE-2.0 | ||
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| 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. | ||
| */ | ||
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| package timeout | ||
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| import ( | ||
| "math" | ||
| "math/rand" | ||
| "sync" | ||
| "time" | ||
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| "github.com/tektoncd/pipeline/pkg/apis/pipeline/v1beta1" | ||
| "go.uber.org/zap" | ||
| ) | ||
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| // Backoff can be used to start timers used to perform exponential backoffs with jitter. | ||
| type Backoff struct { | ||
| logger *zap.SugaredLogger | ||
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| // attempts is a map from the name of the item being backed off to the Attemps object | ||
| // containing its current state | ||
| attempts map[string]Attempts | ||
| // attemptsMut is used to protect access to attempts to ensure that multiple goroutines | ||
| // don't try to update it simultaneously | ||
| attemptsMut sync.Mutex | ||
| // timeoutCallback is the function to call when a timeout has occurred. | ||
| timeoutCallback func(interface{}) | ||
| // timer is used to start timers in separate goroutines | ||
| timer *Timer | ||
| // j is the function that will be called to jitter the backoff intervals. | ||
| j jitterFunc | ||
| // now is the function that will be used to get the current time. | ||
| now nowFunc | ||
| } | ||
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| // Attempts contains state of exponential backoff for a given StatusKey | ||
| type Attempts struct { | ||
| // NumAttempts reflects the number of times a given StatusKey has been delayed | ||
| NumAttempts uint | ||
| // NextAttempt is the point in time at which this backoff expires | ||
| NextAttempt time.Time | ||
| } | ||
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| // jitterFunc is a func applied to a computed backoff duration to remove uniformity | ||
| // from its results. A jitterFunc receives the number of seconds calculated by a | ||
| // backoff algorithm and returns the "jittered" result. | ||
| type jitterFunc func(numSeconds int) (jitteredSeconds int) | ||
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| // nowFunc is a function that is used to get the current time | ||
| type nowFunc func() time.Time | ||
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| // NewBackoff returns an instance of Backoff with the specified stopCh and logger, instantiated | ||
| // and ready to track go routines. | ||
| func NewBackoff( | ||
| stopCh <-chan struct{}, | ||
| logger *zap.SugaredLogger, | ||
| ) *Backoff { | ||
| return &Backoff{ | ||
| timer: NewTimer(stopCh, logger), | ||
| attempts: make(map[string]Attempts), | ||
| j: rand.Intn, | ||
| now: time.Now, | ||
| logger: logger, | ||
| } | ||
| } | ||
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| // Release will remove keys tracking the specified runObj. | ||
| func (b *Backoff) Release(runObj StatusKey) { | ||
| b.attemptsMut.Lock() | ||
| defer b.attemptsMut.Unlock() | ||
| delete(b.attempts, runObj.GetRunKey()) | ||
| } | ||
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| // SetTimeoutCallback will set the function to be called when a timeout has occurred. | ||
| func (b *Backoff) SetTimeoutCallback(f func(interface{})) { | ||
| b.timeoutCallback = f | ||
| } | ||
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| // Get records the number of times it has seen a TaskRun and calculates an | ||
| // appropriate backoff deadline based on that count. Only one backoff per TaskRun | ||
| // may be active at any moment. Requests for a new backoff in the face of an | ||
| // existing one will be ignored and details of the existing backoff will be returned | ||
| // instead. Further, if a calculated backoff time is after the timeout of the TaskRun | ||
| // then the time of the timeout will be returned instead. | ||
| // | ||
| // Returned values are a backoff struct containing a NumAttempts field with the | ||
| // number of attempts performed for this TaskRun and a NextAttempt field | ||
| // describing the time at which the next attempt should be performed. | ||
| // Additionally a boolean is returned indicating whether a backoff for the | ||
| // TaskRun is already in progress. | ||
| func (b *Backoff) Get(tr *v1beta1.TaskRun) (a Attempts, inProgress bool) { | ||
| b.attemptsMut.Lock() | ||
| defer b.attemptsMut.Unlock() | ||
| a = b.attempts[tr.GetRunKey()] | ||
| if b.now().Before(a.NextAttempt) { | ||
| inProgress = true | ||
| return | ||
| } | ||
| a.NumAttempts++ | ||
| a.NextAttempt = b.now().Add(GetExponentialBackoffWithJitter(a.NumAttempts, b.j)) | ||
| duration := timeoutFromSpec((tr.Spec.Timeout)) | ||
| timeoutDeadline := tr.Status.StartTime.Time.Add(duration) | ||
| if timeoutDeadline.Before(a.NextAttempt) { | ||
| a.NextAttempt = timeoutDeadline | ||
| } | ||
| b.attempts[tr.GetRunKey()] = a | ||
| return | ||
| } | ||
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| // GetExponentialBackoffWithJitter will return a number which is 2 to the power | ||
| // of count, but with a jittered value obtained via jf. | ||
| func GetExponentialBackoffWithJitter(count uint, jf jitterFunc) time.Duration { | ||
| exp := float64(count) | ||
| if exp > maxBackoffExponent { | ||
| exp = maxBackoffExponent | ||
| } | ||
| seconds := int(math.Exp2(exp)) | ||
| jittered := 1 + jf(seconds) | ||
| if jittered > maxBackoffSeconds { | ||
| jittered = maxBackoffSeconds | ||
| } | ||
| return time.Duration(jittered) * time.Second | ||
| } | ||
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| // SetTimer creates a blocking function to wait for | ||
| // 1. Stop signal, 2. completion or 3. a given Duration to elapse. | ||
| func (b *Backoff) SetTimer(runObj StatusKey, d time.Duration) { | ||
| if b.timeoutCallback == nil { | ||
| b.logger.Errorf("attempted to set a timer for %q but no callback has been assigned", runObj) | ||
| return | ||
| } | ||
| b.logger.Infof("About to start backoff timer for %s. backing off for %s", runObj.GetRunKey(), d) | ||
| defer b.Release(runObj) | ||
| b.timer.SetTimer(runObj, d, b.timeoutCallback) | ||
| } | ||
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Sounds very odd (at least to me 😉), commenting out this
loggerfrom here fixes race condition. This function invocation within handlePodCreationError and the following SetCondition are somehow causing this.There was a problem hiding this comment.
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Ah, well spotted! It looks like swapping out the
%qfor a%pin this log statement also removes the error. Using%qresults in a string-formatted struct being printed, which probably walks the entire object and accesses all the fields. My hunch is that the%qformatter is not threadsafe in that case? In hindsight this may be why we have theStatusKeyinterface - theGetRunKey()func of TaskRun returns a thread-safe descriptor.There was a problem hiding this comment.
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nice catch, yup it does walk the entire object. The next log statement (using
GetRunKey()onrunObj) looks safe and just prints the address oftaskRunobject instead.