144 lines
3.7 KiB
Go
144 lines
3.7 KiB
Go
// Copyright 2017 Google Inc. All rights reserved.
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//
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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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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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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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package build
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import (
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"errors"
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"fmt"
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"math"
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"os"
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"path/filepath"
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"syscall"
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"time"
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"android/soong/ui/logger"
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)
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// This file provides cross-process synchronization methods
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// i.e. making sure only one Soong process is running for a given output directory
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func BecomeSingletonOrFail(ctx Context, config Config) (lock *fileLock) {
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lockingInfo, err := newLock(config.OutDir())
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if err != nil {
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ctx.Logger.Fatal(err)
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}
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err = lockSynchronous(*lockingInfo, newSleepWaiter(lockfilePollDuration, lockfileTimeout), ctx.Logger)
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if err != nil {
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ctx.Logger.Fatal(err)
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}
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return lockingInfo
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}
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var lockfileTimeout = time.Second * 10
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var lockfilePollDuration = time.Second
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type lockable interface {
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tryLock() error
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Unlock() error
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description() string
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}
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var _ lockable = (*fileLock)(nil)
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type fileLock struct {
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File *os.File
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}
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func (l fileLock) description() (path string) {
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return l.File.Name()
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}
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func (l fileLock) tryLock() (err error) {
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return syscall.Flock(int(l.File.Fd()), syscall.LOCK_EX|syscall.LOCK_NB)
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}
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func (l fileLock) Unlock() (err error) {
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return l.File.Close()
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}
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func lockSynchronous(lock lockable, waiter waiter, logger logger.Logger) (err error) {
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waited := false
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for {
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err = lock.tryLock()
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if err == nil {
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if waited {
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// If we had to wait at all, then when the wait is done, we inform the user
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logger.Printf("Acquired lock on %v; previous Soong process must have completed. Continuing...\n", lock.description())
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}
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return nil
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}
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waited = true
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done, description := waiter.checkDeadline()
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if done {
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return fmt.Errorf("Tried to lock %s, but timed out %s . Make sure no other Soong process is using it",
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lock.description(), waiter.summarize())
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} else {
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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())
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waiter.wait()
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}
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}
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}
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func newLock(basedir string) (lock *fileLock, err error) {
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lockPath := filepath.Join(basedir, ".lock")
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os.MkdirAll(basedir, 0777)
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lockfileDescriptor, err := os.OpenFile(lockPath, os.O_RDWR|os.O_CREATE, 0666)
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if err != nil {
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return nil, errors.New("failed to open " + lockPath)
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}
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lockingInfo := &fileLock{File: lockfileDescriptor}
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return lockingInfo, nil
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}
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type waiter interface {
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wait()
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checkDeadline() (done bool, remainder string)
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summarize() (summary string)
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}
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type sleepWaiter struct {
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sleepInterval time.Duration
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deadline time.Time
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totalWait time.Duration
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}
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var _ waiter = (*sleepWaiter)(nil)
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func newSleepWaiter(interval time.Duration, duration time.Duration) (waiter *sleepWaiter) {
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return &sleepWaiter{interval, time.Now().Add(duration), duration}
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}
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func (s sleepWaiter) wait() {
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time.Sleep(s.sleepInterval)
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}
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func (s *sleepWaiter) checkDeadline() (done bool, remainder string) {
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remainingSleep := s.deadline.Sub(time.Now())
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numSecondsRounded := math.Floor(remainingSleep.Seconds()*10+0.5) / 10
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if remainingSleep > 0 {
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return false, fmt.Sprintf("%vs", numSecondsRounded)
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} else {
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return true, ""
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}
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}
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func (s sleepWaiter) summarize() (summary string) {
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return fmt.Sprintf("polling every %v until %v", s.sleepInterval, s.totalWait)
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}
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