mirror of
https://github.com/ceph/ceph-csi.git
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135 lines
3.7 KiB
Go
135 lines
3.7 KiB
Go
/*
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Copyright 2023 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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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
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package waitgroup
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import (
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"context"
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"fmt"
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"sync"
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)
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// RateLimiter abstracts the rate limiter used by RateLimitedSafeWaitGroup.
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// The implementation must be thread-safe.
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type RateLimiter interface {
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Wait(ctx context.Context) error
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}
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// RateLimiterFactoryFunc is used by the RateLimitedSafeWaitGroup to create a new
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// instance of a RateLimiter that will be used to rate limit the return rate
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// of the active number of request(s). 'count' is the number of requests in
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// flight that are expected to invoke 'Done' on this wait group.
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type RateLimiterFactoryFunc func(count int) (RateLimiter, context.Context, context.CancelFunc)
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// RateLimitedSafeWaitGroup must not be copied after first use.
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type RateLimitedSafeWaitGroup struct {
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wg sync.WaitGroup
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// Once Wait is initiated, all consecutive Done invocation will be
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// rate limited using this rate limiter.
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limiter RateLimiter
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stopCtx context.Context
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mu sync.Mutex
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// wait indicate whether Wait is called, if true,
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// then any Add with positive delta will return error.
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wait bool
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// number of request(s) currently using the wait group
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count int
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}
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// Add adds delta, which may be negative, similar to sync.WaitGroup.
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// If Add with a positive delta happens after Wait, it will return error,
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// which prevent unsafe Add.
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func (wg *RateLimitedSafeWaitGroup) Add(delta int) error {
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wg.mu.Lock()
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defer wg.mu.Unlock()
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if wg.wait && delta > 0 {
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return fmt.Errorf("add with positive delta after Wait is forbidden")
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}
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wg.wg.Add(delta)
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wg.count += delta
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return nil
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}
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// Done decrements the WaitGroup counter, rate limiting is applied only
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// when the wait group is in waiting mode.
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func (wg *RateLimitedSafeWaitGroup) Done() {
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var limiter RateLimiter
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func() {
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wg.mu.Lock()
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defer wg.mu.Unlock()
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wg.count -= 1
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if wg.wait {
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// we are using the limiter outside the scope of the lock
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limiter = wg.limiter
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}
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}()
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defer wg.wg.Done()
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if limiter != nil {
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limiter.Wait(wg.stopCtx)
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}
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}
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// Wait blocks until the WaitGroup counter is zero or a hard limit has elapsed.
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// It returns the number of active request(s) accounted for at the time Wait
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// has been invoked, number of request(s) that have drianed (done using the
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// wait group immediately before Wait returns).
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// Ideally, the both numbers returned should be equal, to indicate that all
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// request(s) using the wait group have released their lock.
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func (wg *RateLimitedSafeWaitGroup) Wait(limiterFactory RateLimiterFactoryFunc) (int, int, error) {
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if limiterFactory == nil {
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return 0, 0, fmt.Errorf("rate limiter factory must be specified")
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}
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var cancel context.CancelFunc
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var countNow, countAfter int
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func() {
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wg.mu.Lock()
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defer wg.mu.Unlock()
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wg.limiter, wg.stopCtx, cancel = limiterFactory(wg.count)
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countNow = wg.count
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wg.wait = true
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}()
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defer cancel()
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// there should be a hard stop, in case request(s) are not responsive
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// enough to invoke Done before the grace period is over.
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waitDoneCh := make(chan struct{})
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go func() {
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defer close(waitDoneCh)
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wg.wg.Wait()
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}()
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var err error
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select {
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case <-wg.stopCtx.Done():
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err = wg.stopCtx.Err()
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case <-waitDoneCh:
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}
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func() {
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wg.mu.Lock()
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defer wg.mu.Unlock()
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countAfter = wg.count
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}()
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return countNow, countAfter, err
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}
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