harness-drone/scheduler/queue/canceller.go

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// Copyright 2019 Drone IO, Inc.
//
// 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
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// 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.
2019-02-19 23:56:41 +00:00
package queue
import (
"context"
"sync"
"time"
)
type canceller struct {
sync.Mutex
subscribers map[chan struct{}]int64
cancelled map[int64]time.Time
}
func newCanceller() *canceller {
return &canceller{
subscribers: make(map[chan struct{}]int64),
cancelled: make(map[int64]time.Time),
}
}
func (c *canceller) Cancel(ctx context.Context, id int64) error {
c.Lock()
c.cancelled[id] = time.Now().Add(time.Minute * 5)
for subscriber, build := range c.subscribers {
if id == build {
close(subscriber)
}
}
c.collect()
c.Unlock()
return nil
}
func (c *canceller) Cancelled(ctx context.Context, id int64) (bool, error) {
subscriber := make(chan struct{})
c.Lock()
c.subscribers[subscriber] = id
c.Unlock()
defer func() {
c.Lock()
delete(c.subscribers, subscriber)
c.Unlock()
}()
for {
select {
case <-ctx.Done():
return false, ctx.Err()
case <-time.After(time.Minute):
c.Lock()
_, ok := c.cancelled[id]
c.Unlock()
if ok {
return true, nil
}
case <-subscriber:
return true, nil
}
}
}
func (c *canceller) collect() {
// the list of cancelled builds is stored with a ttl, and
// is not removed until the ttl is reached. This provides
// adequate window for clients with connectivity issues to
// reconnect and receive notification of cancel events.
now := time.Now()
for build, timestamp := range c.cancelled {
if now.After(timestamp) {
delete(c.cancelled, build)
}
}
}