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| 1 | <?php |
| 2 | |
| 3 | namespace MediaWiki\Settings\Source; |
| 4 | |
| 5 | use DnsSrvDiscoverer; |
| 6 | use GuzzleHttp\Client; |
| 7 | use GuzzleHttp\Exception\ClientException; |
| 8 | use GuzzleHttp\Exception\ConnectException; |
| 9 | use GuzzleHttp\Exception\ServerException; |
| 10 | use GuzzleHttp\Psr7\Uri; |
| 11 | use MediaWiki\Settings\Cache\CacheableSource; |
| 12 | use MediaWiki\Settings\SettingsBuilderException; |
| 13 | use MediaWiki\Settings\Source\Format\JsonFormat; |
| 14 | use UnexpectedValueException; |
| 15 | |
| 16 | /** |
| 17 | * Settings loaded from an etcd server. |
| 18 | * |
| 19 | * @since 1.38 |
| 20 | */ |
| 21 | class EtcdSource implements CacheableSource { |
| 22 | /** |
| 23 | * Default HTTP client connection and request timeout (2 seconds). |
| 24 | */ |
| 25 | private const TIMEOUT = 2; |
| 26 | |
| 27 | /** |
| 28 | * Cache expiry TTL for etcd sources (10 seconds). |
| 29 | * |
| 30 | * @see getExpiryTtl() |
| 31 | * @see CacheableSource::getExpiryTtl() |
| 32 | */ |
| 33 | private const EXPIRY_TTL = 10; |
| 34 | |
| 35 | /** |
| 36 | * Early expiry weight. This value influences the margin by which |
| 37 | * processes are selected to expire cached etcd settings early to avoid |
| 38 | * cache stampedes. |
| 39 | * |
| 40 | * @see getExpiryWeight() |
| 41 | * @see CacheableSource::getExpiryWeight() |
| 42 | */ |
| 43 | private const EXPIRY_WEIGHT = 1.0; |
| 44 | |
| 45 | /** @var Client */ |
| 46 | private $client; |
| 47 | |
| 48 | /** @var Uri */ |
| 49 | private $uri; |
| 50 | |
| 51 | /** @var callable */ |
| 52 | private $mapper; |
| 53 | |
| 54 | /** @var callable */ |
| 55 | private $resolver; |
| 56 | |
| 57 | /** @var JsonFormat */ |
| 58 | private $format; |
| 59 | |
| 60 | /** |
| 61 | * Constructs a new EtcdSource for the given etcd server details. |
| 62 | * |
| 63 | * @param array $params Parameter map: |
| 64 | * - host: Etcd server host/domain. Note that an empty host value will |
| 65 | * result in SRV discovery relative to the host's configured search |
| 66 | * domain. |
| 67 | * - port: Etcd server port. Defaults to 2379. |
| 68 | * - protocol: Endpoint protocol (http/https). Defaults to 'https'. |
| 69 | * - directory: Top level etcd directory to query for settings. |
| 70 | * - discover: Whether to perform SRV discovery on the given |
| 71 | * host/domain. Defaults to true. |
| 72 | * - service: service name used in SRV discovery of the default |
| 73 | * <code>$resolver</code>. Defaults to 'etcd-client-ssl' or |
| 74 | * 'etcd-client' when protocol is 'https' or 'http' respectively. |
| 75 | * @param ?callable $mapper Function that maps etcd entries to valid |
| 76 | * MediaWiki config/schema/php-ini values. Defaults to simply returning |
| 77 | * the structure stored in etcd. |
| 78 | * Signature: function ( array $settings ): array |
| 79 | * @param ?Client $client Guzzle HTTP client used to query etcd. |
| 80 | * @param ?callable $resolver Function that must return an array of server |
| 81 | * hostname/port pairs to try. The default resolver will either: |
| 82 | * - use an explicitly given hostname/port if both are provided |
| 83 | * - otherwise attempt DNS SRV discovery at <code>_etcd._tcp.$host</code> |
| 84 | * - fallback to using the host as the etcd server directly |
| 85 | * Signature: function (): array |
| 86 | * |
| 87 | * @throws SettingsBuilderException if the given host is invalid. |
| 88 | */ |
| 89 | public function __construct( |
| 90 | array $params = [], |
| 91 | ?callable $mapper = null, |
| 92 | ?Client $client = null, |
| 93 | ?callable $resolver = null |
| 94 | ) { |
| 95 | $params += [ |
| 96 | 'host' => '', |
| 97 | 'port' => 2379, |
| 98 | 'protocol' => 'https', |
| 99 | 'directory' => 'mediawiki', |
| 100 | 'discover' => true, |
| 101 | 'service' => null, |
| 102 | ]; |
| 103 | |
| 104 | $service = |
| 105 | $params['service'] ?? |
| 106 | $params['protocol'] == 'https' |
| 107 | ? 'etcd-client-ssl' |
| 108 | : 'etcd-client'; |
| 109 | |
| 110 | $this->mapper = $mapper ?? static function ( $settings ) { |
| 111 | return $settings; |
| 112 | }; |
| 113 | |
| 114 | $this->client = $client ?? new Client( [ |
| 115 | 'timeout' => self::TIMEOUT, |
| 116 | 'connect_timeout' => self::TIMEOUT, |
| 117 | ] ); |
| 118 | |
| 119 | $this->uri = ( new Uri() ) |
| 120 | ->withHost( $params['host'] ) |
| 121 | ->withPort( $params['port'] ) |
| 122 | ->withPath( '/v2/keys/' . trim( $params['directory'], '/' ) . '/' ) |
| 123 | ->withScheme( $params['protocol'] ) |
| 124 | ->withQuery( 'recursive=true' ); |
| 125 | |
| 126 | if ( $resolver !== null ) { |
| 127 | $this->resolver = $resolver; |
| 128 | } elseif ( $params['discover'] ) { |
| 129 | $discoverer = new DnsSrvDiscoverer( $service, 'tcp', $params['host'] ); |
| 130 | $this->uri = $this->uri->withHost( $discoverer->getSrvName() )->withPort( null ); |
| 131 | $this->resolver = static function () use ( $discoverer ) { |
| 132 | return $discoverer->getServers(); |
| 133 | }; |
| 134 | } else { |
| 135 | $this->resolver = static function () use ( $params ) { |
| 136 | return [ [ $params['host'], $params['port'] ] ]; |
| 137 | }; |
| 138 | } |
| 139 | |
| 140 | $this->format = new JsonFormat(); |
| 141 | } |
| 142 | |
| 143 | /** |
| 144 | * Allow stale results from etcd sources in case all servers become |
| 145 | * temporarily unavailable. |
| 146 | * |
| 147 | * @return bool |
| 148 | */ |
| 149 | public function allowsStaleLoad(): bool { |
| 150 | return true; |
| 151 | } |
| 152 | |
| 153 | /** |
| 154 | * Loads and returns settings from the etcd server. |
| 155 | * |
| 156 | * @throws SettingsBuilderException |
| 157 | * @return array |
| 158 | */ |
| 159 | public function load(): array { |
| 160 | $lastException = false; |
| 161 | |
| 162 | foreach ( ( $this->resolver )() as [ $host, $port ] ) { |
| 163 | try { |
| 164 | return $this->loadFromEtcdServer( $host, $port ); |
| 165 | } catch ( ConnectException | ServerException $e ) { |
| 166 | $lastException = $e; |
| 167 | } |
| 168 | } |
| 169 | |
| 170 | throw new SettingsBuilderException( |
| 171 | 'failed to load settings from etcd source: {source}: {message}', |
| 172 | [ |
| 173 | 'source' => $this, |
| 174 | 'message' => $lastException ? $lastException->getMessage() : '', |
| 175 | ] |
| 176 | ); |
| 177 | } |
| 178 | |
| 179 | /** |
| 180 | * The cache expiry TTL (in seconds) for this source. |
| 181 | * |
| 182 | * @return int |
| 183 | */ |
| 184 | public function getExpiryTtl(): int { |
| 185 | return self::EXPIRY_TTL; |
| 186 | } |
| 187 | |
| 188 | /** |
| 189 | * Coefficient used in determining early expiration of cached settings to |
| 190 | * avoid stampedes. |
| 191 | * |
| 192 | * @return float |
| 193 | */ |
| 194 | public function getExpiryWeight(): float { |
| 195 | return self::EXPIRY_WEIGHT; |
| 196 | } |
| 197 | |
| 198 | /** |
| 199 | * Returns a naive hash key for use in caching based on an etcd request |
| 200 | * URL constructed using the etcd request URL. In the case where SRV |
| 201 | * discovery is performed, the host in the URL will be the SRV record |
| 202 | * name. |
| 203 | * |
| 204 | * @return string |
| 205 | */ |
| 206 | public function getHashKey(): string { |
| 207 | return (string)$this->uri; |
| 208 | } |
| 209 | |
| 210 | /** |
| 211 | * Returns this etcd source as a string. |
| 212 | * |
| 213 | * @return string |
| 214 | */ |
| 215 | public function __toString(): string { |
| 216 | return (string)$this->uri; |
| 217 | } |
| 218 | |
| 219 | /** |
| 220 | * @param string $host |
| 221 | * @param int $port |
| 222 | * |
| 223 | * @throws SettingsBuilderException |
| 224 | * @return array |
| 225 | */ |
| 226 | private function loadFromEtcdServer( string $host, int $port ): array { |
| 227 | $uri = $this->uri->withHost( $host )->withPort( $port ); |
| 228 | |
| 229 | try { |
| 230 | $response = $this->client->get( $uri, [ 'http_errors' => true ] ); |
| 231 | } catch ( ClientException $e ) { |
| 232 | throw new SettingsBuilderException( |
| 233 | 'bad request made to etcd server: {message}: uri {uri}', |
| 234 | [ 'message' => $e->getMessage(), 'uri' => $uri ] |
| 235 | ); |
| 236 | } |
| 237 | |
| 238 | $settings = []; |
| 239 | |
| 240 | try { |
| 241 | $resp = $this->format->decode( $response->getBody()->getContents() ); |
| 242 | |
| 243 | if ( |
| 244 | !isset( $resp['node'] ) || !is_array( $resp['node'] ) |
| 245 | || !isset( $resp['node']['dir'] ) || !$resp['node']['dir'] |
| 246 | ) { |
| 247 | throw new SettingsBuilderException( |
| 248 | 'etcd request to {uri} did not return a valid directory node', |
| 249 | [ 'uri' => $uri ] |
| 250 | ); |
| 251 | } |
| 252 | |
| 253 | $this->parseDirectory( |
| 254 | $resp['node'], |
| 255 | strlen( $resp['node']['key'] ) + 1, |
| 256 | $settings |
| 257 | ); |
| 258 | } catch ( UnexpectedValueException $e ) { |
| 259 | throw new SettingsBuilderException( |
| 260 | 'failed to parse etcd response body: {message}', |
| 261 | [ 'message' => $e->getMessage() ] |
| 262 | ); |
| 263 | } |
| 264 | |
| 265 | return ( $this->mapper )( $settings ); |
| 266 | } |
| 267 | |
| 268 | /** |
| 269 | * @param array $dir Directory node. |
| 270 | * @param int $prefix Length of the directory prefix to remove. |
| 271 | * @param array &$settings Flattened settings array to which to write. |
| 272 | */ |
| 273 | private function parseDirectory( array $dir, int $prefix, array &$settings ) { |
| 274 | foreach ( $dir['nodes'] as $node ) { |
| 275 | if ( isset( $node['dir'] ) && $node['dir'] ) { |
| 276 | $this->parseDirectory( $node, $prefix, $settings ); |
| 277 | } else { |
| 278 | $key = substr( $node['key'], $prefix ); |
| 279 | $value = $this->format->decode( $node['value'] ); |
| 280 | $settings[$key] = $value['val']; |
| 281 | } |
| 282 | } |
| 283 | } |
| 284 | } |