MediaWiki  REL1_31
ExternalStoreDB.php
Go to the documentation of this file.
1 <?php
29 
47  public function fetchFromURL( $url ) {
48  list( $cluster, $id, $itemID ) = $this->parseURL( $url );
49  $ret = $this->fetchBlob( $cluster, $id, $itemID );
50 
51  if ( $itemID !== false && $ret !== false ) {
52  return $ret->getItem( $itemID );
53  }
54 
55  return $ret;
56  }
57 
67  public function batchFetchFromURLs( array $urls ) {
68  $batched = $inverseUrlMap = [];
69  foreach ( $urls as $url ) {
70  list( $cluster, $id, $itemID ) = $this->parseURL( $url );
71  $batched[$cluster][$id][] = $itemID;
72  // false $itemID gets cast to int, but should be ok
73  // since we do === from the $itemID in $batched
74  $inverseUrlMap[$cluster][$id][$itemID] = $url;
75  }
76  $ret = [];
77  foreach ( $batched as $cluster => $batchByCluster ) {
78  $res = $this->batchFetchBlobs( $cluster, $batchByCluster );
80  foreach ( $res as $id => $blob ) {
81  foreach ( $batchByCluster[$id] as $itemID ) {
82  $url = $inverseUrlMap[$cluster][$id][$itemID];
83  if ( $itemID === false ) {
84  $ret[$url] = $blob;
85  } else {
86  $ret[$url] = $blob->getItem( $itemID );
87  }
88  }
89  }
90  }
91 
92  return $ret;
93  }
94 
95  public function store( $location, $data ) {
96  $dbw = $this->getMaster( $location );
97  $dbw->insert( $this->getTable( $dbw ),
98  [ 'blob_text' => $data ],
99  __METHOD__ );
100  $id = $dbw->insertId();
101  if ( !$id ) {
102  throw new MWException( __METHOD__ . ': no insert ID' );
103  }
104 
105  return "DB://$location/$id";
106  }
107 
108  public function isReadOnly( $location ) {
109  return ( $this->getLoadBalancer( $location )->getReadOnlyReason() !== false );
110  }
111 
118  private function getLoadBalancer( $cluster ) {
119  $lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
120  return $lbFactory->getExternalLB( $cluster );
121  }
122 
129  public function getSlave( $cluster ) {
131 
132  $lb = $this->getLoadBalancer( $cluster );
133  $domainId = $this->getDomainId( $lb->getServerInfo( $lb->getWriterIndex() ) );
134 
135  if ( !in_array( "DB://" . $cluster, (array)$wgDefaultExternalStore ) ) {
136  wfDebug( "read only external store\n" );
137  $lb->allowLagged( true );
138  } else {
139  wfDebug( "writable external store\n" );
140  }
141 
142  $db = $lb->getConnectionRef( DB_REPLICA, [], $domainId );
143  $db->clearFlag( DBO_TRX ); // sanity
144 
145  return $db;
146  }
147 
154  public function getMaster( $cluster ) {
155  $lb = $this->getLoadBalancer( $cluster );
156  $domainId = $this->getDomainId( $lb->getServerInfo( $lb->getWriterIndex() ) );
157 
158  $db = $lb->getMaintenanceConnectionRef( DB_MASTER, [], $domainId );
159  $db->clearFlag( DBO_TRX ); // sanity
160 
161  return $db;
162  }
163 
168  private function getDomainId( array $server ) {
169  if ( isset( $this->params['wiki'] ) ) {
170  return $this->params['wiki']; // explicit domain
171  }
172 
173  if ( isset( $server['dbname'] ) ) {
174  // T200471: for b/c, treat any "dbname" field as forcing which database to use.
175  // MediaWiki/LoadBalancer previously did not enforce any concept of a local DB
176  // domain, but rather assumed that the LB server configuration matched $wgDBname.
177  // This check is useful when the external storage DB for this cluster does not use
178  // the same name as the corresponding "main" DB(s) for wikis.
179  $domain = new DatabaseDomain(
180  $server['dbname'],
181  $server['schema'] ?? null,
182  $server['tablePrefix'] ?? ''
183  );
184 
185  return $domain->getId();
186  }
187 
188  return false; // local LB domain
189  }
190 
197  public function getTable( $db ) {
198  $table = $db->getLBInfo( 'blobs table' );
199  if ( is_null( $table ) ) {
200  $table = 'blobs';
201  }
202 
203  return $table;
204  }
205 
215  private function fetchBlob( $cluster, $id, $itemID ) {
222  static $externalBlobCache = [];
223 
224  $cacheID = ( $itemID === false ) ? "$cluster/$id" : "$cluster/$id/";
225  if ( isset( $externalBlobCache[$cacheID] ) ) {
226  wfDebugLog( 'ExternalStoreDB-cache',
227  "ExternalStoreDB::fetchBlob cache hit on $cacheID" );
228 
229  return $externalBlobCache[$cacheID];
230  }
231 
232  wfDebugLog( 'ExternalStoreDB-cache',
233  "ExternalStoreDB::fetchBlob cache miss on $cacheID" );
234 
235  $dbr = $this->getSlave( $cluster );
236  $ret = $dbr->selectField( $this->getTable( $dbr ),
237  'blob_text', [ 'blob_id' => $id ], __METHOD__ );
238  if ( $ret === false ) {
239  wfDebugLog( 'ExternalStoreDB',
240  "ExternalStoreDB::fetchBlob master fallback on $cacheID" );
241  // Try the master
242  $dbw = $this->getMaster( $cluster );
243  $ret = $dbw->selectField( $this->getTable( $dbw ),
244  'blob_text', [ 'blob_id' => $id ], __METHOD__ );
245  if ( $ret === false ) {
246  wfDebugLog( 'ExternalStoreDB',
247  "ExternalStoreDB::fetchBlob master failed to find $cacheID" );
248  }
249  }
250  if ( $itemID !== false && $ret !== false ) {
251  // Unserialise object; caller extracts item
252  $ret = unserialize( $ret );
253  }
254 
255  $externalBlobCache = [ $cacheID => $ret ];
256 
257  return $ret;
258  }
259 
268  private function batchFetchBlobs( $cluster, array $ids ) {
269  $dbr = $this->getSlave( $cluster );
270  $res = $dbr->select( $this->getTable( $dbr ),
271  [ 'blob_id', 'blob_text' ], [ 'blob_id' => array_keys( $ids ) ], __METHOD__ );
272  $ret = [];
273  if ( $res !== false ) {
274  $this->mergeBatchResult( $ret, $ids, $res );
275  }
276  if ( $ids ) {
277  wfDebugLog( __CLASS__, __METHOD__ .
278  " master fallback on '$cluster' for: " .
279  implode( ',', array_keys( $ids ) ) );
280  // Try the master
281  $dbw = $this->getMaster( $cluster );
282  $res = $dbw->select( $this->getTable( $dbr ),
283  [ 'blob_id', 'blob_text' ],
284  [ 'blob_id' => array_keys( $ids ) ],
285  __METHOD__ );
286  if ( $res === false ) {
287  wfDebugLog( __CLASS__, __METHOD__ . " master failed on '$cluster'" );
288  } else {
289  $this->mergeBatchResult( $ret, $ids, $res );
290  }
291  }
292  if ( $ids ) {
293  wfDebugLog( __CLASS__, __METHOD__ .
294  " master on '$cluster' failed locating items: " .
295  implode( ',', array_keys( $ids ) ) );
296  }
297 
298  return $ret;
299  }
300 
307  private function mergeBatchResult( array &$ret, array &$ids, $res ) {
308  foreach ( $res as $row ) {
309  $id = $row->blob_id;
310  $itemIDs = $ids[$id];
311  unset( $ids[$id] ); // to track if everything is found
312  if ( count( $itemIDs ) === 1 && reset( $itemIDs ) === false ) {
313  // single result stored per blob
314  $ret[$id] = $row->blob_text;
315  } else {
316  // multi result stored per blob
317  $ret[$id] = unserialize( $row->blob_text );
318  }
319  }
320  }
321 
326  protected function parseURL( $url ) {
327  $path = explode( '/', $url );
328 
329  return [
330  $path[2], // cluster
331  $path[3], // id
332  isset( $path[4] ) ? $path[4] : false // itemID
333  ];
334  }
335 }
ExternalStoreDB\batchFetchBlobs
batchFetchBlobs( $cluster, array $ids)
Fetch multiple blob items out of the database.
Definition: ExternalStoreDB.php:268
ExternalStoreMedium
Accessable external objects in a particular storage medium.
Definition: ExternalStoreMedium.php:30
ExternalStoreDB\getSlave
getSlave( $cluster)
Get a replica DB connection for the specified cluster.
Definition: ExternalStoreDB.php:129
use
Apache License January AND DISTRIBUTION Definitions License shall mean the terms and conditions for use
Definition: APACHE-LICENSE-2.0.txt:10
ExternalStoreDB\parseURL
parseURL( $url)
Definition: ExternalStoreDB.php:326
ExternalStoreDB
DB accessible external objects.
Definition: ExternalStoreDB.php:38
ExternalStoreDB\store
store( $location, $data)
Insert a data item into a given location.
Definition: ExternalStoreDB.php:95
array
the array() calling protocol came about after MediaWiki 1.4rc1.
ExternalStoreDB\batchFetchFromURLs
batchFetchFromURLs(array $urls)
Fetch data from given external store URLs.
Definition: ExternalStoreDB.php:67
$ret
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 & $ret
Definition: hooks.txt:2005
unserialize
unserialize( $serialized)
Definition: ApiMessage.php:192
$res
$res
Definition: database.txt:21
$wgDefaultExternalStore
array $wgDefaultExternalStore
The place to put new revisions, false to put them in the local text table.
Definition: DefaultSettings.php:2171
ExternalStoreDB\fetchBlob
fetchBlob( $cluster, $id, $itemID)
Fetch a blob item out of the database; a cache of the last-loaded blob will be kept so that multiple ...
Definition: ExternalStoreDB.php:215
wfDebugLog
wfDebugLog( $logGroup, $text, $dest='all', array $context=[])
Send a line to a supplementary debug log file, if configured, or main debug log if not.
Definition: GlobalFunctions.php:1087
DBO_TRX
const DBO_TRX
Definition: defines.php:12
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
Wikimedia\Rdbms\IDatabase
Basic database interface for live and lazy-loaded relation database handles.
Definition: IDatabase.php:38
ExternalStoreDB\getDomainId
getDomainId(array $server)
Definition: ExternalStoreDB.php:168
$dbr
$dbr
Definition: testCompression.php:50
Wikimedia\Rdbms\MaintainableDBConnRef
Helper class to handle automatically marking connections as reusable (via RAII pattern) as well handl...
Definition: MaintainableDBConnRef.php:13
ExternalStoreDB\getLoadBalancer
getLoadBalancer( $cluster)
Get a LoadBalancer for the specified cluster.
Definition: ExternalStoreDB.php:118
MWException
MediaWiki exception.
Definition: MWException.php:26
$blob
$blob
Definition: testCompression.php:65
ExternalStoreDB\isReadOnly
isReadOnly( $location)
Check if a given location is read-only.
Definition: ExternalStoreDB.php:108
global
when a variable name is used in a it is silently declared as a new masking the global
Definition: design.txt:95
DB_REPLICA
const DB_REPLICA
Definition: defines.php:25
DB_MASTER
const DB_MASTER
Definition: defines.php:26
wfDebug
wfDebug( $text, $dest='all', array $context=[])
Sends a line to the debug log if enabled or, optionally, to a comment in output.
Definition: GlobalFunctions.php:994
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
ExternalStoreDB\getTable
getTable( $db)
Get the 'blobs' table name for this database.
Definition: ExternalStoreDB.php:197
ExternalStoreDB\fetchFromURL
fetchFromURL( $url)
The provided URL is in the form of DB://cluster/id or DB://cluster/id/itemid for concatened storage.
Definition: ExternalStoreDB.php:47
$urls
$urls
Definition: opensearch_desc.php:76
Wikimedia\Rdbms\DBConnRef
Helper class to handle automatically marking connections as reusable (via RAII pattern) as well handl...
Definition: DBConnRef.php:15
$path
$path
Definition: NoLocalSettings.php:25
as
This document is intended to provide useful advice for parties seeking to redistribute MediaWiki to end users It s targeted particularly at maintainers for Linux since it s been observed that distribution packages of MediaWiki often break We ve consistently had to recommend that users seeking support use official tarballs instead of their distribution s and this often solves whatever problem the user is having It would be nice if this could such as
Definition: distributors.txt:22
MediaWikiServices
injection txt This is an overview of how MediaWiki makes use of dependency injection The design described here grew from the discussion of RFC T384 The term dependency this means that anything an object needs to operate should be injected from the the object itself should only know narrow no concrete implementation of the logic it relies on The requirement to inject everything typically results in an architecture that based on two main types of and essentially stateless service objects that use other service objects to operate on the value objects As of the beginning MediaWiki is only starting to use the DI approach Much of the code still relies on global state or direct resulting in a highly cyclical dependency MediaWikiServices
Definition: injection.txt:25
Wikimedia\Rdbms\DatabaseDomain
Class to handle database/prefix specification for IDatabase domains.
Definition: DatabaseDomain.php:28
ExternalStoreDB\mergeBatchResult
mergeBatchResult(array &$ret, array &$ids, $res)
Helper function for self::batchFetchBlobs for merging master/replica DB results.
Definition: ExternalStoreDB.php:307
false
processing should stop and the error should be shown to the user * false
Definition: hooks.txt:187
ExternalStoreDB\getMaster
getMaster( $cluster)
Get a master database connection for the specified cluster.
Definition: ExternalStoreDB.php:154
Wikimedia\Rdbms\ILoadBalancer
Database cluster connection, tracking, load balancing, and transaction manager interface.
Definition: ILoadBalancer.php:78