MediaWiki  REL1_31
EtcdConfig.php
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1 <?php
21 use Psr\Log\LoggerAwareInterface;
22 use Psr\Log\LoggerInterface;
23 use Wikimedia\ObjectFactory;
24 use Wikimedia\WaitConditionLoop;
25 
31 class 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;
50  private $baseCacheTTL;
52  private $skewCacheTTL;
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 }
DnsSrvDiscoverer
Definition: DnsSrvDiscoverer.php:26
EtcdConfig\$http
MultiHttpClient $http
Definition: EtcdConfig.php:33
MultiHttpClient
Class to handle concurrent HTTP requests.
Definition: MultiHttpClient.php:48
directory
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
use
Apache License January AND DISTRIBUTION Definitions License shall mean the terms and conditions for use
Definition: APACHE-LICENSE-2.0.txt:10
HashBagOStuff
Simple store for keeping values in an associative array for the current process.
Definition: HashBagOStuff.php:31
EtcdConfig\__construct
__construct(array $params)
Definition: EtcdConfig.php:68
$response
this hook is for auditing only $response
Definition: hooks.txt:783
array
the array() calling protocol came about after MediaWiki 1.4rc1.
IP\combineHostAndPort
static combineHostAndPort( $host, $port, $defaultPort=false)
Given a host name and a port, combine them into host/port string like you might find in a URL.
Definition: IP.php:315
EtcdConfig\fetchAllFromEtcd
fetchAllFromEtcd()
Definition: EtcdConfig.php:209
EtcdConfig\fetchAllFromEtcdServer
fetchAllFromEtcdServer( $address)
Definition: EtcdConfig.php:238
EtcdConfig
Interface for configuration instances.
Definition: EtcdConfig.php:31
unserialize
unserialize( $serialized)
Definition: ApiMessage.php:192
$params
$params
Definition: styleTest.css.php:40
BagOStuff
interface is intended to be more or less compatible with the PHP memcached client.
Definition: BagOStuff.php:47
$fullName
$fullName
Definition: opensearch_desc.php:63
http
Apache License January http
Definition: APACHE-LICENSE-2.0.txt:6
true
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:2006
php
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
EtcdConfig\load
load()
Definition: EtcdConfig.php:130
EtcdConfig\$directory
string $directory
Definition: EtcdConfig.php:46
Config
Interface for configuration instances.
Definition: Config.php:28
EtcdConfig\setLogger
setLogger(LoggerInterface $logger)
Definition: EtcdConfig.php:101
ConfigException
Exceptions for config failures.
Definition: ConfigException.php:28
EtcdConfig\$logger
LoggerInterface $logger
Definition: EtcdConfig.php:39
EtcdConfig\$skewCacheTTL
int $skewCacheTTL
Definition: EtcdConfig.php:52
EtcdConfig\unserialize
unserialize( $string)
Definition: EtcdConfig.php:326
list
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
EtcdConfig\$procCache
array $procCache
Definition: EtcdConfig.php:37
EtcdConfig\parseDirectory
parseDirectory( $dirName, $dirNode, &$config)
Recursively parse a directory node and populate the array passed by reference, throwing EtcdConfigPar...
Definition: EtcdConfig.php:292
$value
$value
Definition: styleTest.css.php:45
EtcdConfig\$baseCacheTTL
int $baseCacheTTL
Definition: EtcdConfig.php:50
EtcdConfig\$srvCache
BagOStuff $srvCache
Definition: EtcdConfig.php:35
$name
Allows to change the fields on the form that will be generated $name
Definition: hooks.txt:302
EtcdConfig\$host
string $host
Definition: EtcdConfig.php:42
as
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
Definition: distributors.txt:22
EtcdConfig\$protocol
string $protocol
Definition: EtcdConfig.php:44
EtcdConfig\has
has( $name)
Check whether a configuration option is set for the given name.
Definition: EtcdConfig.php:106
EtcdConfig\$timeout
int $timeout
Definition: EtcdConfig.php:54
EtcdConfig\getModifiedIndex
getModifiedIndex()
Definition: EtcdConfig.php:122
EtcdConfig\$encoding
string $encoding
Definition: EtcdConfig.php:48
EtcdConfig\parseResponse
parseResponse( $rbody)
Parse a response body, throwing EtcdConfigParseError if there is a validation error.
Definition: EtcdConfig.php:269
EtcdConfigParseError
Definition: EtcdConfigParseError.php:3
$e
div flags Integer display flags(NO_ACTION_LINK, NO_EXTRA_USER_LINKS) 'LogException' returning false will NOT prevent logging $e
Definition: hooks.txt:2171