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1 |
1 | <?php |
2 | |
3 | namespace MediaWiki\Extension\EventLogging; |
4 | |
5 | use JsonSerializable; |
6 | use MediaWiki\Http\HttpRequestFactory; |
7 | use MediaWiki\Json\FormatJson; |
8 | use MediaWiki\MediaWikiServices; |
9 | use stdClass; |
10 | use Wikimedia\ObjectCache\BagOStuff; |
11 | |
12 | /** |
13 | * Represents a schema revision on a remote wiki. |
14 | * Handles retrieval (via HTTP) and local caching. |
15 | */ |
16 | class RemoteSchema implements JsonSerializable { |
17 | |
18 | public const LOCK_TIMEOUT = 20; |
19 | |
20 | /** @var string */ |
21 | public $title; |
22 | /** @var int */ |
23 | public $revision; |
24 | /** @var BagOStuff */ |
25 | public $cache; |
26 | /** @var HttpRequestFactory */ |
27 | public $httpRequestFactory; |
28 | /** @var string */ |
29 | public $key; |
30 | /** @var array|false */ |
31 | public $content = false; |
32 | |
33 | /** |
34 | * Constructor. |
35 | * @param string $title |
36 | * @param int $revision |
37 | * @param BagOStuff|null $cache (optional) cache client. |
38 | * @param HttpRequestFactory|null $httpRequestFactory (optional) HttpRequestFactory client. |
39 | */ |
40 | public function __construct( $title, $revision, $cache = null, $httpRequestFactory = null ) { |
41 | global $wgEventLoggingSchemaApiUri; |
42 | |
43 | $this->title = $title; |
44 | $this->revision = $revision; |
45 | $this->cache = $cache ?: MediaWikiServices::getInstance() |
46 | ->getObjectCacheFactory()->getInstance( CACHE_ANYTHING ); |
47 | $this->httpRequestFactory = $httpRequestFactory ?: MediaWikiServices::getInstance()->getHttpRequestFactory(); |
48 | $this->key = $this->cache->makeGlobalKey( |
49 | 'eventlogging-schema', |
50 | $wgEventLoggingSchemaApiUri, |
51 | $revision |
52 | ); |
53 | } |
54 | |
55 | /** |
56 | * Retrieves schema content. |
57 | * @return array|bool Schema or false if irretrievable. |
58 | */ |
59 | public function get() { |
60 | if ( $this->content ) { |
61 | return $this->content; |
62 | } |
63 | |
64 | $this->content = $this->memcGet(); |
65 | if ( $this->content ) { |
66 | return $this->content; |
67 | } |
68 | |
69 | $this->content = $this->httpGet(); |
70 | if ( $this->content ) { |
71 | $this->memcSet(); |
72 | } |
73 | |
74 | return $this->content; |
75 | } |
76 | |
77 | /** |
78 | * Returns an object containing serializable properties. |
79 | * @return array |
80 | */ |
81 | public function jsonSerialize(): array { |
82 | return [ |
83 | 'schema' => $this->get() ?: new stdClass(), |
84 | 'revision' => $this->revision |
85 | ]; |
86 | } |
87 | |
88 | /** |
89 | * Retrieves content from memcached. |
90 | * @return array|bool Schema or false if not in cache. |
91 | */ |
92 | protected function memcGet() { |
93 | return $this->cache->get( $this->key ); |
94 | } |
95 | |
96 | /** |
97 | * Store content in memcached. |
98 | * @return bool |
99 | */ |
100 | protected function memcSet() { |
101 | return $this->cache->set( $this->key, $this->content ); |
102 | } |
103 | |
104 | /** |
105 | * Retrieves the schema using HTTP. |
106 | * Uses a memcached lock to avoid cache stampedes. |
107 | * @return array|bool Schema or false if unable to fetch. |
108 | */ |
109 | protected function httpGet() { |
110 | $uri = $this->getUri(); |
111 | if ( !$this->lock() ) { |
112 | EventLogging::getLogger()->warning( |
113 | 'Failed to get lock for requesting {schema_uri}.', |
114 | [ 'schema_uri' => $uri ] |
115 | ); |
116 | return false; |
117 | } |
118 | $raw = $this->httpRequestFactory->get( $uri, [ |
119 | 'timeout' => self::LOCK_TIMEOUT * 0.8 |
120 | ], __METHOD__ ); |
121 | $content = FormatJson::decode( $raw, true ); |
122 | if ( !$content ) { |
123 | EventLogging::getLogger()->error( |
124 | 'Request to {schema_uri} failed.', |
125 | [ 'schema_uri' => $uri ] |
126 | ); |
127 | } |
128 | return $content ?: false; |
129 | } |
130 | |
131 | /** |
132 | * Acquire a mutex lock for HTTP retrieval. |
133 | * @return bool Whether lock was successfully acquired. |
134 | */ |
135 | protected function lock() { |
136 | return $this->cache->add( $this->key . ':lock', 1, self::LOCK_TIMEOUT ); |
137 | } |
138 | |
139 | /** |
140 | * Constructs URI for retrieving schema from remote wiki. |
141 | * @return string URI. |
142 | */ |
143 | protected function getUri() { |
144 | global $wgEventLoggingSchemaApiUri; |
145 | |
146 | return wfAppendQuery( $wgEventLoggingSchemaApiUri, [ |
147 | 'action' => 'jsonschema', |
148 | 'revid' => $this->revision, |
149 | 'formatversion' => 2, |
150 | 'format' => 'json', |
151 | ] ); |
152 | } |
153 | } |