MediaWiki REL1_32
EtcdConfig.php
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1<?php
21use Psr\Log\LoggerAwareInterface;
22use Psr\Log\LoggerInterface;
23use Wikimedia\ObjectFactory;
24use Wikimedia\WaitConditionLoop;
25
31class EtcdConfig implements Config, LoggerAwareInterface {
33 private $http;
35 private $srvCache;
37 private $procCache;
39 private $logger;
40
42 private $host;
44 private $protocol;
46 private $directory;
48 private $encoding;
54 private $timeout;
55
68 public function __construct( array $params ) {
69 $params += [
70 'protocol' => 'http',
71 'encoding' => 'JSON',
72 'cacheTTL' => 10,
73 'skewTTL' => 1,
74 'timeout' => 2
75 ];
76
77 $this->host = $params['host'];
78 $this->protocol = $params['protocol'];
79 $this->directory = trim( $params['directory'], '/' );
80 $this->encoding = $params['encoding'];
81 $this->skewCacheTTL = $params['skewTTL'];
82 $this->baseCacheTTL = max( $params['cacheTTL'] - $this->skewCacheTTL, 0 );
83 $this->timeout = $params['timeout'];
84
85 if ( !isset( $params['cache'] ) ) {
86 $this->srvCache = new HashBagOStuff();
87 } elseif ( $params['cache'] instanceof BagOStuff ) {
88 $this->srvCache = $params['cache'];
89 } else {
90 $this->srvCache = ObjectFactory::getObjectFromSpec( $params['cache'] );
91 }
92
93 $this->logger = new Psr\Log\NullLogger();
94 $this->http = new MultiHttpClient( [
95 'connTimeout' => $this->timeout,
96 'reqTimeout' => $this->timeout,
97 'logger' => $this->logger
98 ] );
99 }
100
101 public function setLogger( LoggerInterface $logger ) {
102 $this->logger = $logger;
103 $this->http->setLogger( $logger );
104 }
105
106 public function has( $name ) {
107 $this->load();
108
109 return array_key_exists( $name, $this->procCache['config'] );
110 }
111
112 public function get( $name ) {
113 $this->load();
114
115 if ( !array_key_exists( $name, $this->procCache['config'] ) ) {
116 throw new ConfigException( "No entry found for '$name'." );
117 }
118
119 return $this->procCache['config'][$name];
120 }
121
122 public function getModifiedIndex() {
123 $this->load();
124 return $this->procCache['modifiedIndex'];
125 }
126
130 private function load() {
131 if ( $this->procCache !== null ) {
132 return; // already loaded
133 }
134
135 $now = microtime( true );
136 $key = $this->srvCache->makeGlobalKey(
137 __CLASS__,
138 $this->host,
139 $this->directory
140 );
141
142 // Get the cached value or block until it is regenerated (by this or another thread)...
143 $data = null; // latest config info
144 $error = null; // last error message
145 $loop = new WaitConditionLoop(
146 function () use ( $key, $now, &$data, &$error ) {
147 // Check if the values are in cache yet...
148 $data = $this->srvCache->get( $key );
149 if ( is_array( $data ) && $data['expires'] > $now ) {
150 $this->logger->debug( "Found up-to-date etcd configuration cache." );
151
152 return WaitConditionLoop::CONDITION_REACHED;
153 }
154
155 // Cache is either empty or stale;
156 // refresh the cache from etcd, using a mutex to reduce stampedes...
157 if ( $this->srvCache->lock( $key, 0, $this->baseCacheTTL ) ) {
158 try {
159 $etcdResponse = $this->fetchAllFromEtcd();
160 $error = $etcdResponse['error'];
161 if ( is_array( $etcdResponse['config'] ) ) {
162 // Avoid having all servers expire cache keys at the same time
163 $expiry = microtime( true ) + $this->baseCacheTTL;
164 $expiry += mt_rand( 0, 1e6 ) / 1e6 * $this->skewCacheTTL;
165 $data = [
166 'config' => $etcdResponse['config'],
167 'expires' => $expiry,
168 'modifiedIndex' => $etcdResponse['modifiedIndex']
169 ];
170 $this->srvCache->set( $key, $data, BagOStuff::TTL_INDEFINITE );
171
172 $this->logger->info( "Refreshed stale etcd configuration cache." );
173
174 return WaitConditionLoop::CONDITION_REACHED;
175 } else {
176 $this->logger->error( "Failed to fetch configuration: $error" );
177 if ( !$etcdResponse['retry'] ) {
178 // Fail fast since the error is likely to keep happening
179 return WaitConditionLoop::CONDITION_FAILED;
180 }
181 }
182 } finally {
183 $this->srvCache->unlock( $key ); // release mutex
184 }
185 }
186
187 if ( is_array( $data ) ) {
188 $this->logger->info( "Using stale etcd configuration cache." );
189
190 return WaitConditionLoop::CONDITION_REACHED;
191 }
192
193 return WaitConditionLoop::CONDITION_CONTINUE;
194 },
196 );
197
198 if ( $loop->invoke() !== WaitConditionLoop::CONDITION_REACHED ) {
199 // No cached value exists and etcd query failed; throw an error
200 throw new ConfigException( "Failed to load configuration from etcd: $error" );
201 }
202
203 $this->procCache = $data;
204 }
205
209 public function fetchAllFromEtcd() {
210 // TODO: inject DnsSrvDiscoverer in order to be able to test this method
211 $dsd = new DnsSrvDiscoverer( $this->host );
212 $servers = $dsd->getServers();
213 if ( !$servers ) {
214 return $this->fetchAllFromEtcdServer( $this->host );
215 }
216
217 do {
218 // Pick a random etcd server from dns
219 $server = $dsd->pickServer( $servers );
220 $host = IP::combineHostAndPort( $server['target'], $server['port'] );
221 // Try to load the config from this particular server
222 $response = $this->fetchAllFromEtcdServer( $host );
223 if ( is_array( $response['config'] ) || $response['retry'] ) {
224 break;
225 }
226
227 // Avoid the server next time if that failed
228 $servers = $dsd->removeServer( $server, $servers );
229 } while ( $servers );
230
231 return $response;
232 }
233
238 protected function fetchAllFromEtcdServer( $address ) {
239 // Retrieve all the values under the MediaWiki config directory
240 list( $rcode, $rdesc, /* $rhdrs */, $rbody, $rerr ) = $this->http->run( [
241 'method' => 'GET',
242 'url' => "{$this->protocol}://{$address}/v2/keys/{$this->directory}/?recursive=true",
243 'headers' => [ 'content-type' => 'application/json' ]
244 ] );
245
246 $response = [ 'config' => null, 'error' => null, 'retry' => false, 'modifiedIndex' => 0 ];
247
248 static $terminalCodes = [ 404 => true ];
249 if ( $rcode < 200 || $rcode > 399 ) {
250 $response['error'] = strlen( $rerr ) ? $rerr : "HTTP $rcode ($rdesc)";
251 $response['retry'] = empty( $terminalCodes[$rcode] );
252 return $response;
253 }
254
255 try {
256 $parsedResponse = $this->parseResponse( $rbody );
257 } catch ( EtcdConfigParseError $e ) {
258 $parsedResponse = [ 'error' => $e->getMessage() ];
259 }
260 return array_merge( $response, $parsedResponse );
261 }
262
269 protected function parseResponse( $rbody ) {
270 $info = json_decode( $rbody, true );
271 if ( $info === null ) {
272 throw new EtcdConfigParseError( "Error unserializing JSON response." );
273 }
274 if ( !isset( $info['node'] ) || !is_array( $info['node'] ) ) {
275 throw new EtcdConfigParseError(
276 "Unexpected JSON response: Missing or invalid node at top level." );
277 }
278 $config = [];
279 $lastModifiedIndex = $this->parseDirectory( '', $info['node'], $config );
280 return [ 'modifiedIndex' => $lastModifiedIndex, 'config' => $config ];
281 }
282
292 protected function parseDirectory( $dirName, $dirNode, &$config ) {
293 $lastModifiedIndex = 0;
294 if ( !isset( $dirNode['nodes'] ) ) {
295 throw new EtcdConfigParseError(
296 "Unexpected JSON response in dir '$dirName'; missing 'nodes' list." );
297 }
298 if ( !is_array( $dirNode['nodes'] ) ) {
299 throw new EtcdConfigParseError(
300 "Unexpected JSON response in dir '$dirName'; 'nodes' is not an array." );
301 }
302
303 foreach ( $dirNode['nodes'] as $node ) {
304 $baseName = basename( $node['key'] );
305 $fullName = $dirName === '' ? $baseName : "$dirName/$baseName";
306 if ( !empty( $node['dir'] ) ) {
307 $lastModifiedIndex = max(
308 $this->parseDirectory( $fullName, $node, $config ),
309 $lastModifiedIndex );
310 } else {
311 $value = $this->unserialize( $node['value'] );
312 if ( !is_array( $value ) || !array_key_exists( 'val', $value ) ) {
313 throw new EtcdConfigParseError( "Failed to parse value for '$fullName'." );
314 }
315 $lastModifiedIndex = max( $node['modifiedIndex'], $lastModifiedIndex );
316 $config[$fullName] = $value['val'];
317 }
318 }
319 return $lastModifiedIndex;
320 }
321
326 private function unserialize( $string ) {
327 if ( $this->encoding === 'YAML' ) {
328 return yaml_parse( $string );
329 } else { // JSON
330 return json_decode( $string, true );
331 }
332 }
333}
Apache License January http
Apache License January AND DISTRIBUTION Definitions License shall mean the terms and conditions for use
unserialize( $serialized)
Class representing a cache/ephemeral data store.
Definition BagOStuff.php:58
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)
Check whether a configuration option is set for the given 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 multiple 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
This document is intended to provide useful advice for parties seeking to redistribute MediaWiki to end users It s targeted particularly at maintainers for Linux since it s been observed that distribution packages of MediaWiki often break We ve consistently had to recommend that users seeking support use official tarballs instead of their distribution s and this often solves whatever problem the user is having It would be nice if this could such as
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:2055
Allows to change the fields on the form that will be generated $name
Definition hooks.txt:302
this hook is for auditing only $response
Definition hooks.txt:813
returning false will NOT prevent logging $e
Definition hooks.txt:2226
injection txt This is an overview of how MediaWiki makes use of dependency injection The design described here grew from the discussion of RFC T384 The term dependency this means that anything an object needs to operate should be injected from the the object itself should only know narrow no concrete implementation of the logic it relies on The requirement to inject everything typically results in an architecture that based on two main types of and essentially stateless service objects that use other service objects to operate on the value objects As of the beginning MediaWiki is only starting to use the DI approach Much of the code still relies on global state or direct resulting in a highly cyclical dependency which acts as the top level factory for services in MediaWiki which can be used to gain access to default instances of various services MediaWikiServices however also allows new services to be defined and default services to be redefined Services are defined or redefined by providing a callback the instantiator that will return a new instance of the service When it will create an instance of MediaWikiServices and populate it with the services defined in the files listed by thereby bootstrapping the DI framework Per $wgServiceWiringFiles lists includes ServiceWiring php
Definition injection.txt:37
Interface for configuration instances.
Definition Config.php:28
The wiki should then use memcached to cache various data To use multiple just add more items to the array To increase the weight of a make its entry a array("192.168.0.1:11211", 2))
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