1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
|
<?php
/**
* Piwik - free/libre analytics platform
*
* @link http://piwik.org
* @license http://www.gnu.org/licenses/gpl-3.0.html GPL v3 or later
*
*/
namespace Piwik\Concurrency;
use Piwik\Common;
class Lock
{
const MAX_KEY_LEN = 70;
/**
* @var LockBackend
*/
private $backend;
private $lockKeyStart;
private $lockKey = null;
private $lockValue = null;
private $defaultTtl = null;
public function __construct(LockBackend $backend, $lockKeyStart, $defaultTtl = null)
{
$this->backend = $backend;
$this->lockKeyStart = $lockKeyStart;
$this->lockKey = $this->lockKeyStart;
$this->defaultTtl = $defaultTtl;
}
public function reexpireLock()
{
$this->expireLock($this->defaultTtl);
}
public function getNumberOfAcquiredLocks()
{
return count($this->getAllAcquiredLockKeys());
}
public function getAllAcquiredLockKeys()
{
return $this->backend->getKeysMatchingPattern($this->lockKeyStart . '*');
}
public function execute($id, $callback)
{
if (Common::mb_strlen($id) > self::MAX_KEY_LEN) {
// Lock key might be too long for DB column, so we hash it but leave the start of the original as well
// to make it more readable
$md5Len = 32;
$id = Common::mb_substr($id, 0, self::MAX_KEY_LEN - $md5Len - 1) . md5($id);
}
$i = 0;
while (!$this->acquireLock($id)) {
$i++;
usleep( 100 * 1000 ); // 100ms
if ($i > 50) { // give up after 5seconds (50 * 100ms)
throw new \Exception('Could not get the lock for ID: ' . $id);
}
};
try {
return $callback();
} finally {
$this->unlock();
}
}
public function acquireLock($id, $ttlInSeconds = 60)
{
$this->lockKey = $this->lockKeyStart . $id;
$lockValue = substr(Common::generateUniqId(), 0, 12);
$locked = $this->backend->setIfNotExists($this->lockKey, $lockValue, $ttlInSeconds);
if ($locked) {
$this->lockValue = $lockValue;
}
return $locked;
}
public function isLocked()
{
if (!$this->lockValue) {
return false;
}
return $this->lockValue === $this->backend->get($this->lockKey);
}
public function unlock()
{
if ($this->lockValue) {
$this->backend->deleteIfKeyHasValue($this->lockKey, $this->lockValue);
$this->lockValue = null;
}
}
public function expireLock($ttlInSeconds)
{
if ($ttlInSeconds > 0) {
if ($this->lockValue) {
$success = $this->backend->expireIfKeyHasValue($this->lockKey, $this->lockValue, $ttlInSeconds);
if (!$success) {
$value = $this->backend->get($this->lockKey);
$message = sprintf('Failed to expire key %s (%s / %s).', $this->lockKey, $this->lockValue, (string)$value);
if ($value === false) {
Common::printDebug($message . ' It seems like the key already expired as it no longer exists.');
} elseif (!empty($value) && $value == $this->lockValue) {
Common::printDebug($message . ' We still have the lock but for some reason it did not expire.');
} elseif (!empty($value)) {
Common::printDebug($message . ' This lock has been acquired by another process/server.');
} else {
Common::printDebug($message . ' Failed to expire key.');
}
return false;
}
return true;
} else {
Common::printDebug('Lock is not acquired, cannot update expiration.');
}
} else {
Common::printDebug('Provided TTL ' . $ttlInSeconds . ' is in valid in Lock::expireLock().');
}
return false;
}
}
|
