1// Copyright 2017 Google Inc. All rights reserved.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15package build
16
17import (
18	"errors"
19	"fmt"
20	"math"
21	"os"
22	"path/filepath"
23	"syscall"
24	"time"
25
26	"android/soong/ui/logger"
27)
28
29// This file provides cross-process synchronization methods
30// i.e. making sure only one Soong process is running for a given output directory
31
32func BecomeSingletonOrFail(ctx Context, config Config) (lock *fileLock) {
33	lockingInfo, err := newLock(config.OutDir())
34	if err != nil {
35		ctx.Logger.Fatal(err)
36	}
37	lockfilePollDuration := time.Second
38	lockfileTimeout := time.Second * 10
39	if envTimeout := os.Getenv("SOONG_LOCK_TIMEOUT"); envTimeout != "" {
40		lockfileTimeout, err = time.ParseDuration(envTimeout)
41		if err != nil {
42			ctx.Logger.Fatalf("failure parsing SOONG_LOCK_TIMEOUT %q: %s", envTimeout, err)
43		}
44	}
45	err = lockSynchronous(*lockingInfo, newSleepWaiter(lockfilePollDuration, lockfileTimeout), ctx.Logger)
46	if err != nil {
47		ctx.Logger.Fatal(err)
48	}
49	return lockingInfo
50}
51
52type lockable interface {
53	tryLock() error
54	Unlock() error
55	description() string
56}
57
58var _ lockable = (*fileLock)(nil)
59
60type fileLock struct {
61	File *os.File
62}
63
64func (l fileLock) description() (path string) {
65	return l.File.Name()
66}
67func (l fileLock) tryLock() (err error) {
68	return syscall.Flock(int(l.File.Fd()), syscall.LOCK_EX|syscall.LOCK_NB)
69}
70func (l fileLock) Unlock() (err error) {
71	return l.File.Close()
72}
73
74func lockSynchronous(lock lockable, waiter waiter, logger logger.Logger) (err error) {
75
76	waited := false
77
78	for {
79		err = lock.tryLock()
80		if err == nil {
81			if waited {
82				// If we had to wait at all, then when the wait is done, we inform the user
83				logger.Printf("Acquired lock on %v; previous Soong process must have completed. Continuing...\n", lock.description())
84			}
85			return nil
86		}
87
88		done, description := waiter.checkDeadline()
89
90		if !waited {
91			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())
92		}
93
94		waited = true
95
96		if done {
97			return fmt.Errorf("Tried to lock %s, but timed out %s . Make sure no other Soong process is using it",
98				lock.description(), waiter.summarize())
99		} else {
100			waiter.wait()
101		}
102	}
103}
104
105func newLock(basedir string) (lock *fileLock, err error) {
106	lockPath := filepath.Join(basedir, ".lock")
107
108	os.MkdirAll(basedir, 0777)
109	lockfileDescriptor, err := os.OpenFile(lockPath, os.O_RDWR|os.O_CREATE, 0666)
110	if err != nil {
111		return nil, errors.New("failed to open " + lockPath)
112	}
113	lockingInfo := &fileLock{File: lockfileDescriptor}
114
115	return lockingInfo, nil
116}
117
118type waiter interface {
119	wait()
120	checkDeadline() (done bool, remainder string)
121	summarize() (summary string)
122}
123
124type sleepWaiter struct {
125	sleepInterval time.Duration
126	deadline      time.Time
127
128	totalWait time.Duration
129}
130
131var _ waiter = (*sleepWaiter)(nil)
132
133func newSleepWaiter(interval time.Duration, duration time.Duration) (waiter *sleepWaiter) {
134	return &sleepWaiter{interval, time.Now().Add(duration), duration}
135}
136
137func (s sleepWaiter) wait() {
138	time.Sleep(s.sleepInterval)
139}
140func (s *sleepWaiter) checkDeadline() (done bool, remainder string) {
141	remainingSleep := s.deadline.Sub(time.Now())
142	numSecondsRounded := math.Floor(remainingSleep.Seconds()*10+0.5) / 10
143	if remainingSleep > 0 {
144		return false, fmt.Sprintf("%vs", numSecondsRounded)
145	} else {
146		return true, ""
147	}
148}
149func (s sleepWaiter) summarize() (summary string) {
150	return fmt.Sprintf("polling every %v until %v", s.sleepInterval, s.totalWait)
151}
152