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
|
<?php
namespace React\Dns\Query;
use React\Cache\CacheInterface;
use React\Dns\Model\Message;
use React\Promise\Promise;
final class CachingExecutor implements ExecutorInterface
{
/**
* Default TTL for negative responses (NXDOMAIN etc.).
*
* @internal
*/
const TTL = 60;
private $executor;
private $cache;
public function __construct(ExecutorInterface $executor, CacheInterface $cache)
{
$this->executor = $executor;
$this->cache = $cache;
}
public function query(Query $query)
{
$id = $query->name . ':' . $query->type . ':' . $query->class;
$cache = $this->cache;
$that = $this;
$executor = $this->executor;
$pending = $cache->get($id);
return new Promise(function ($resolve, $reject) use ($query, $id, $cache, $executor, &$pending, $that) {
$pending->then(
function ($message) use ($query, $id, $cache, $executor, &$pending, $that) {
// return cached response message on cache hit
if ($message !== null) {
return $message;
}
// perform DNS lookup if not already cached
return $pending = $executor->query($query)->then(
function (Message $message) use ($cache, $id, $that) {
// DNS response message received => store in cache when not truncated and return
if (!$message->tc) {
$cache->set($id, $message, $that->ttl($message));
}
return $message;
}
);
}
)->then($resolve, function ($e) use ($reject, &$pending) {
$reject($e);
$pending = null;
});
}, function ($_, $reject) use (&$pending, $query) {
$reject(new \RuntimeException('DNS query for ' . $query->describe() . ' has been cancelled'));
$pending->cancel();
$pending = null;
});
}
/**
* @param Message $message
* @return int
* @internal
*/
public function ttl(Message $message)
{
// select TTL from answers (should all be the same), use smallest value if available
// @link https://tools.ietf.org/html/rfc2181#section-5.2
$ttl = null;
foreach ($message->answers as $answer) {
if ($ttl === null || $answer->ttl < $ttl) {
$ttl = $answer->ttl;
}
}
if ($ttl === null) {
$ttl = self::TTL;
}
return $ttl;
}
}
|
