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// Copyright 2017 Google Inc. All rights reserved.
//
// 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.
package build
import (
"errors"
"fmt"
"math"
"os"
"path/filepath"
"syscall"
"time"
"android/soong/ui/logger"
)
// This file provides cross-process synchronization methods
// i.e. making sure only one Soong process is running for a given output directory
func BecomeSingletonOrFail(ctx Context, config Config) (lock *fileLock) {
lockingInfo, err := newLock(config.OutDir())
if err != nil {
ctx.Logger.Fatal(err)
}
err = lockSynchronous(*lockingInfo, newSleepWaiter(lockfilePollDuration, lockfileTimeout), ctx.Logger)
if err != nil {
ctx.Logger.Fatal(err)
}
return lockingInfo
}
var lockfileTimeout = time.Second * 10
var lockfilePollDuration = time.Second
type lockable interface {
tryLock() error
Unlock() error
description() string
}
var _ lockable = (*fileLock)(nil)
type fileLock struct {
File *os.File
}
func (l fileLock) description() (path string) {
return l.File.Name()
}
func (l fileLock) tryLock() (err error) {
return syscall.Flock(int(l.File.Fd()), syscall.LOCK_EX|syscall.LOCK_NB)
}
func (l fileLock) Unlock() (err error) {
return l.File.Close()
}
func lockSynchronous(lock lockable, waiter waiter, logger logger.Logger) (err error) {
waited := false
for {
err = lock.tryLock()
if err == nil {
if waited {
// If we had to wait at all, then when the wait is done, we inform the user
logger.Printf("Acquired lock on %v; previous Soong process must have completed. Continuing...\n", lock.description())
}
return nil
}
waited = true
done, description := waiter.checkDeadline()
if done {
return fmt.Errorf("Tried to lock %s, but timed out %s . Make sure no other Soong process is using it",
lock.description(), waiter.summarize())
} else {
logger.Printf("Waiting up to %s to lock %v to ensure no other Soong process is running in the same output directory\n", description, lock.description())
waiter.wait()
}
}
}
func newLock(basedir string) (lock *fileLock, err error) {
lockPath := filepath.Join(basedir, ".lock")
os.MkdirAll(basedir, 0777)
lockfileDescriptor, err := os.OpenFile(lockPath, os.O_RDWR|os.O_CREATE, 0666)
if err != nil {
return nil, errors.New("failed to open " + lockPath)
}
lockingInfo := &fileLock{File: lockfileDescriptor}
return lockingInfo, nil
}
type waiter interface {
wait()
checkDeadline() (done bool, remainder string)
summarize() (summary string)
}
type sleepWaiter struct {
sleepInterval time.Duration
deadline time.Time
totalWait time.Duration
}
var _ waiter = (*sleepWaiter)(nil)
func newSleepWaiter(interval time.Duration, duration time.Duration) (waiter *sleepWaiter) {
return &sleepWaiter{interval, time.Now().Add(duration), duration}
}
func (s sleepWaiter) wait() {
time.Sleep(s.sleepInterval)
}
func (s *sleepWaiter) checkDeadline() (done bool, remainder string) {
remainingSleep := s.deadline.Sub(time.Now())
numSecondsRounded := math.Floor(remainingSleep.Seconds()*10+0.5) / 10
if remainingSleep > 0 {
return false, fmt.Sprintf("%vs", numSecondsRounded)
} else {
return true, ""
}
}
func (s sleepWaiter) summarize() (summary string) {
return fmt.Sprintf("polling every %v until %v", s.sleepInterval, s.totalWait)
}
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