MediaWiki  master
ExternalStoreAccess.php
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1 <?php
21 use Psr\Log\LoggerAwareInterface;
22 use Psr\Log\LoggerInterface;
23 use Psr\Log\NullLogger;
24 use Wikimedia\RequestTimeout\TimeoutException;
25 
43 class ExternalStoreAccess implements LoggerAwareInterface {
45  private $storeFactory;
47  private $logger;
48 
53  public function __construct( ExternalStoreFactory $factory, LoggerInterface $logger = null ) {
54  $this->storeFactory = $factory;
55  $this->logger = $logger ?: new NullLogger();
56  }
57 
58  public function setLogger( LoggerInterface $logger ) {
59  $this->logger = $logger;
60  }
61 
72  public function fetchFromURL( $url, array $params = [] ) {
73  return $this->storeFactory->getStoreForUrl( $url, $params )->fetchFromURL( $url );
74  }
75 
86  public function fetchFromURLs( array $urls, array $params = [] ) {
87  $batches = $this->storeFactory->getUrlsByProtocol( $urls );
88  $retval = [];
89  foreach ( $batches as $proto => $batchedUrls ) {
90  $store = $this->storeFactory->getStore( $proto, $params );
91  $retval += $store->batchFetchFromURLs( $batchedUrls );
92  }
93  // invalid, not found, db dead, etc.
94  $missing = array_diff( $urls, array_keys( $retval ) );
95  foreach ( $missing as $url ) {
96  $retval[$url] = false;
97  }
98 
99  return $retval;
100  }
101 
117  public function insert( $data, array $params = [], array $tryStores = null ) {
118  $tryStores = $tryStores ?? $this->storeFactory->getWriteBaseUrls();
119  if ( !$tryStores ) {
120  throw new ExternalStoreException( "List of external stores provided is empty." );
121  }
122 
123  $error = false; // track the last exception thrown
124  $readOnlyCount = 0; // track if a store was read-only
125  while ( count( $tryStores ) > 0 ) {
126  $index = mt_rand( 0, count( $tryStores ) - 1 );
127  $storeUrl = $tryStores[$index];
128 
129  $this->logger->debug( __METHOD__ . ": trying $storeUrl" );
130 
131  $store = $this->storeFactory->getStoreForUrl( $storeUrl, $params );
132  if ( $store === false ) {
133  throw new ExternalStoreException( "Invalid external storage protocol - $storeUrl" );
134  }
135 
136  $location = $this->storeFactory->getStoreLocationFromUrl( $storeUrl );
137  try {
138  if ( $store->isReadOnly( $location ) ) {
139  $readOnlyCount++;
140  $msg = 'read only';
141  } else {
142  $url = $store->store( $location, $data );
143  if ( strlen( $url ) ) {
144  // A store accepted the write; done!
145  return $url;
146  }
147  throw new ExternalStoreException(
148  "No URL returned by storage medium ($storeUrl)"
149  );
150  }
151  } catch ( TimeoutException $e ) {
152  throw $e;
153  } catch ( Exception $ex ) {
154  $error = $ex;
155  $msg = 'caught ' . get_class( $error ) . ' exception: ' . $error->getMessage();
156  }
157 
158  unset( $tryStores[$index] ); // Don't try this one again!
159  $tryStores = array_values( $tryStores ); // Must have consecutive keys
160  $this->logger->error(
161  "Unable to store text to external storage {store_path} ({failure})",
162  [ 'store_path' => $storeUrl, 'failure' => $msg ]
163  );
164  }
165 
166  // We only get here when all stores failed.
167  if ( $error ) {
168  // At least one store threw an exception. Re-throw the most recent one.
169  throw $error;
170  } elseif ( $readOnlyCount ) {
171  // If no exceptions where thrown and we get here,
172  // this should mean that all stores were in read-only mode.
173  throw new ReadOnlyError();
174  } else {
175  // We shouldn't get here. If there were no failures, this method should have returned
176  // from inside the body of the loop.
177  throw new LogicException( "Unexpected failure to store text to external store" );
178  }
179  }
180 
186  public function isReadOnly( $storeUrls = null ) {
187  if ( $storeUrls === null ) {
188  $storeUrls = $this->storeFactory->getWriteBaseUrls();
189  } else {
190  $storeUrls = is_array( $storeUrls ) ? $storeUrls : [ $storeUrls ];
191  }
192 
193  if ( !$storeUrls ) {
194  return false; // no stores exists which can be "read only"
195  }
196 
197  foreach ( $storeUrls as $storeUrl ) {
198  $store = $this->storeFactory->getStoreForUrl( $storeUrl );
199  $location = $this->storeFactory->getStoreLocationFromUrl( $storeUrl );
200  if ( $store !== false && !$store->isReadOnly( $location ) ) {
201  return false; // at least one store is not read-only
202  }
203  }
204 
205  return true; // all stores are read-only
206  }
207 }
This is the main interface for fetching or inserting objects with ExternalStore.
insert( $data, array $params=[], array $tryStores=null)
Insert data into storage and return the assigned URL.
setLogger(LoggerInterface $logger)
fetchFromURL( $url, array $params=[])
Fetch data from given URL.
fetchFromURLs(array $urls, array $params=[])
Fetch data from multiple URLs with a minimum of round trips.
isReadOnly( $storeUrls=null)
__construct(ExternalStoreFactory $factory, LoggerInterface $logger=null)
Show an error when the wiki is locked/read-only and the user tries to do something that requires writ...