MediaWiki REL1_30
EtcdConfig.php
Go to the documentation of this file.
1<?php
21use Psr\Log\LoggerAwareInterface;
22use Psr\Log\LoggerInterface;
23use Wikimedia\WaitConditionLoop;
24
30class EtcdConfig implements Config, LoggerAwareInterface {
32 private $http;
34 private $srvCache;
36 private $procCache;
38 private $logger;
39
41 private $host;
43 private $protocol;
45 private $directory;
47 private $encoding;
53 private $timeout;
54
67 public function __construct( array $params ) {
68 $params += [
69 'protocol' => 'http',
70 'encoding' => 'JSON',
71 'cacheTTL' => 10,
72 'skewTTL' => 1,
73 'timeout' => 2
74 ];
75
76 $this->host = $params['host'];
77 $this->protocol = $params['protocol'];
78 $this->directory = trim( $params['directory'], '/' );
79 $this->encoding = $params['encoding'];
80 $this->skewCacheTTL = $params['skewTTL'];
81 $this->baseCacheTTL = max( $params['cacheTTL'] - $this->skewCacheTTL, 0 );
82 $this->timeout = $params['timeout'];
83
84 if ( !isset( $params['cache'] ) ) {
85 $this->srvCache = new HashBagOStuff();
86 } elseif ( $params['cache'] instanceof BagOStuff ) {
87 $this->srvCache = $params['cache'];
88 } else {
89 $this->srvCache = ObjectFactory::getObjectFromSpec( $params['cache'] );
90 }
91
92 $this->logger = new Psr\Log\NullLogger();
93 $this->http = new MultiHttpClient( [
94 'connTimeout' => $this->timeout,
95 'reqTimeout' => $this->timeout,
96 'logger' => $this->logger
97 ] );
98 }
99
100 public function setLogger( LoggerInterface $logger ) {
101 $this->logger = $logger;
102 $this->http->setLogger( $logger );
103 }
104
105 public function has( $name ) {
106 $this->load();
107
108 return array_key_exists( $name, $this->procCache['config'] );
109 }
110
111 public function get( $name ) {
112 $this->load();
113
114 if ( !array_key_exists( $name, $this->procCache['config'] ) ) {
115 throw new ConfigException( "No entry found for '$name'." );
116 }
117
118 return $this->procCache['config'][$name];
119 }
120
124 private function load() {
125 if ( $this->procCache !== null ) {
126 return; // already loaded
127 }
128
129 $now = microtime( true );
130 $key = $this->srvCache->makeGlobalKey(
131 __CLASS__,
132 $this->host,
133 $this->directory
134 );
135
136 // Get the cached value or block until it is regenerated (by this or another thread)...
137 $data = null; // latest config info
138 $error = null; // last error message
139 $loop = new WaitConditionLoop(
140 function () use ( $key, $now, &$data, &$error ) {
141 // Check if the values are in cache yet...
142 $data = $this->srvCache->get( $key );
143 if ( is_array( $data ) && $data['expires'] > $now ) {
144 $this->logger->debug( "Found up-to-date etcd configuration cache." );
145
146 return WaitConditionLoop::CONDITION_REACHED;
147 }
148
149 // Cache is either empty or stale;
150 // refresh the cache from etcd, using a mutex to reduce stampedes...
151 if ( $this->srvCache->lock( $key, 0, $this->baseCacheTTL ) ) {
152 try {
153 list( $config, $error, $retry ) = $this->fetchAllFromEtcd();
154 if ( is_array( $config ) ) {
155 // Avoid having all servers expire cache keys at the same time
156 $expiry = microtime( true ) + $this->baseCacheTTL;
157 $expiry += mt_rand( 0, 1e6 ) / 1e6 * $this->skewCacheTTL;
158
159 $data = [ 'config' => $config, 'expires' => $expiry ];
160 $this->srvCache->set( $key, $data, BagOStuff::TTL_INDEFINITE );
161
162 $this->logger->info( "Refreshed stale etcd configuration cache." );
163
164 return WaitConditionLoop::CONDITION_REACHED;
165 } else {
166 $this->logger->error( "Failed to fetch configuration: $error" );
167 if ( !$retry ) {
168 // Fail fast since the error is likely to keep happening
169 return WaitConditionLoop::CONDITION_FAILED;
170 }
171 }
172 } finally {
173 $this->srvCache->unlock( $key ); // release mutex
174 }
175 }
176
177 if ( is_array( $data ) ) {
178 $this->logger->info( "Using stale etcd configuration cache." );
179
180 return WaitConditionLoop::CONDITION_REACHED;
181 }
182
183 return WaitConditionLoop::CONDITION_CONTINUE;
184 },
186 );
187
188 if ( $loop->invoke() !== WaitConditionLoop::CONDITION_REACHED ) {
189 // No cached value exists and etcd query failed; throw an error
190 throw new ConfigException( "Failed to load configuration from etcd: $error" );
191 }
192
193 $this->procCache = $data;
194 }
195
199 public function fetchAllFromEtcd() {
200 $dsd = new DnsSrvDiscoverer( $this->host );
201 $servers = $dsd->getServers();
202 if ( !$servers ) {
203 return $this->fetchAllFromEtcdServer( $this->host );
204 }
205
206 do {
207 // Pick a random etcd server from dns
208 $server = $dsd->pickServer( $servers );
209 $host = IP::combineHostAndPort( $server['target'], $server['port'] );
210 // Try to load the config from this particular server
211 list( $config, $error, $retry ) = $this->fetchAllFromEtcdServer( $host );
212 if ( is_array( $config ) || !$retry ) {
213 break;
214 }
215
216 // Avoid the server next time if that failed
217 $servers = $dsd->removeServer( $server, $servers );
218 } while ( $servers );
219
220 return [ $config, $error, $retry ];
221 }
222
227 protected function fetchAllFromEtcdServer( $address ) {
228 // Retrieve all the values under the MediaWiki config directory
229 list( $rcode, $rdesc, /* $rhdrs */, $rbody, $rerr ) = $this->http->run( [
230 'method' => 'GET',
231 'url' => "{$this->protocol}://{$address}/v2/keys/{$this->directory}/?recursive=true",
232 'headers' => [ 'content-type' => 'application/json' ]
233 ] );
234
235 static $terminalCodes = [ 404 => true ];
236 if ( $rcode < 200 || $rcode > 399 ) {
237 return [
238 null,
239 strlen( $rerr ) ? $rerr : "HTTP $rcode ($rdesc)",
240 empty( $terminalCodes[$rcode] )
241 ];
242 }
243 try {
244 return [ $this->parseResponse( $rbody ), null, false ];
245 } catch ( EtcdConfigParseError $e ) {
246 return [ null, $e->getMessage(), false ];
247 }
248 }
249
256 protected function parseResponse( $rbody ) {
257 $info = json_decode( $rbody, true );
258 if ( $info === null ) {
259 throw new EtcdConfigParseError( "Error unserializing JSON response." );
260 }
261 if ( !isset( $info['node'] ) || !is_array( $info['node'] ) ) {
262 throw new EtcdConfigParseError(
263 "Unexpected JSON response: Missing or invalid node at top level." );
264 }
265 $config = [];
266 $this->parseDirectory( '', $info['node'], $config );
267 return $config;
268 }
269
278 protected function parseDirectory( $dirName, $dirNode, &$config ) {
279 if ( !isset( $dirNode['nodes'] ) ) {
280 throw new EtcdConfigParseError(
281 "Unexpected JSON response in dir '$dirName'; missing 'nodes' list." );
282 }
283 if ( !is_array( $dirNode['nodes'] ) ) {
284 throw new EtcdConfigParseError(
285 "Unexpected JSON response in dir '$dirName'; 'nodes' is not an array." );
286 }
287
288 foreach ( $dirNode['nodes'] as $node ) {
289 $baseName = basename( $node['key'] );
290 $fullName = $dirName === '' ? $baseName : "$dirName/$baseName";
291 if ( !empty( $node['dir'] ) ) {
292 $this->parseDirectory( $fullName, $node, $config );
293 } else {
294 $value = $this->unserialize( $node['value'] );
295 if ( !is_array( $value ) || !array_key_exists( 'val', $value ) ) {
296 throw new EtcdConfigParseError( "Failed to parse value for '$fullName'." );
297 }
298
299 $config[$fullName] = $value['val'];
300 }
301 }
302 }
303
308 private function unserialize( $string ) {
309 if ( $this->encoding === 'YAML' ) {
310 return yaml_parse( $string );
311 } else { // JSON
312 return json_decode( $string, true );
313 }
314 }
315}
Apache License January http
unserialize( $serialized)
interface is intended to be more or less compatible with the PHP memcached client.
Definition BagOStuff.php:47
Exceptions for config failures.
Interface for configuration instances.
string $encoding
int $skewCacheTTL
unserialize( $string)
string $host
string $protocol
MultiHttpClient $http
parseDirectory( $dirName, $dirNode, &$config)
Recursively parse a directory node and populate the array passed by reference, throwing EtcdConfigPar...
array $procCache
LoggerInterface $logger
string $directory
setLogger(LoggerInterface $logger)
__construct(array $params)
BagOStuff $srvCache
int $baseCacheTTL
has( $name)
parseResponse( $rbody)
Parse a response body, throwing EtcdConfigParseError if there is a validation error.
fetchAllFromEtcdServer( $address)
Simple store for keeping values in an associative array for the current process.
Class to handle concurrent HTTP requests.
deferred txt A few of the database updates required by various functions here can be deferred until after the result page is displayed to the user For updating the view updating the linked to tables after a etc PHP does not yet have any way to tell the server to actually return and disconnect while still running these but it might have such a feature in the future We handle these by creating a deferred update object and putting those objects on a global list
Definition deferred.txt:11
null means default in associative array with keys and values unescaped Should be merged with default with a value of false meaning to suppress the attribute in associative array with keys and values unescaped noclasses just before the function returns a value If you return true
Definition hooks.txt:1976
Allows to change the fields on the form that will be generated $name
Definition hooks.txt:302
processing should stop and the error should be shown to the user * false
Definition hooks.txt:187
returning false will NOT prevent logging $e
Definition hooks.txt:2146
The most up to date schema for the tables in the database will always be tables sql in the maintenance directory
Definition schema.txt:2
$params