includes/api/ApiStashEdit.php

   1 <?php
   2 /**
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation; either version 2 of the License, or
   6  * (at your option) any later version.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  16  * http://www.gnu.org/copyleft/gpl.html
  17  *
  18  * @file
  19  * @author Aaron Schulz
  20  */
  21
  22 use MediaWiki\Logger\LoggerFactory;
  23
  24 /**
  25  * Prepare an edit in shared cache so that it can be reused on edit
  26  *
  27  * This endpoint can be called via AJAX as the user focuses on the edit
  28  * summary box. By the time of submission, the parse may have already
  29  * finished, and can be immediately used on page save. Certain parser
  30  * functions like {{REVISIONID}} or {{CURRENTTIME}} may cause the cache
  31  * to not be used on edit. Template and files used are check for changes
  32  * since the output was generated. The cache TTL is also kept low for sanity.
  33  *
  34  * @ingroup API
  35  * @since 1.25
  36  */
  37 class ApiStashEdit extends ApiBase {
  38         const ERROR_NONE = 'stashed';
  39         const ERROR_PARSE = 'error_parse';
  40         const ERROR_CACHE = 'error_cache';
  41         const ERROR_UNCACHEABLE = 'uncacheable';
  42         const ERROR_BUSY = 'busy';
  43
  44         const PRESUME_FRESH_TTL_SEC = 30;
  45         const MAX_CACHE_TTL = 300; // 5 minutes
  46
  47         public function execute() {
  48                 $user = $this->getUser();
  49                 $params = $this->extractRequestParams();
  50
  51                 if ( $user->isBot() ) { // sanity
  52                         $this->dieUsage( 'This interface is not supported for bots', 'botsnotsupported' );
  53                 }
  54
  55                 $cache = ObjectCache::getLocalClusterInstance();
  56                 $page = $this->getTitleOrPageId( $params );
  57                 $title = $page->getTitle();
  58
  59                 if ( !ContentHandler::getForModelID( $params['contentmodel'] )
  60                         ->isSupportedFormat( $params['contentformat'] )
  61                 ) {
  62                         $this->dieUsage( 'Unsupported content model/format', 'badmodelformat' );
  63                 }
  64
  65                 if ( strlen( $params['stashedtexthash'] ) ) {
  66                         // Load from cache since the client indicates the text is the same as last stash
  67                         $textHash = $params['stashedtexthash'];
  68                         $textKey = $cache->makeKey( 'stashedit', 'text', $textHash );
  69                         $text = $cache->get( $textKey );
  70                         if ( !is_string( $text ) ) {
  71                                 $this->dieUsage( 'No stashed text found with the given hash', 'missingtext' );
  72                         }
  73                 } elseif ( $params['text'] !== null ) {
  74                         // Trim and fix newlines so the key SHA1's match (see WebRequest::getText())
  75                         $text = rtrim( str_replace( "\r\n", "\n", $params['text'] ) );
  76                         $textHash = sha1( $text );
  77                 } else {
  78                         $this->dieUsage(
  79                                 'The text or stashedtexthash parameter must be given', 'missingtextparam' );
  80                 }
  81
  82                 $textContent = ContentHandler::makeContent(
  83                         $text, $title, $params['contentmodel'], $params['contentformat'] );
  84
  85                 $page = WikiPage::factory( $title );
  86                 if ( $page->exists() ) {
  87                         // Page exists: get the merged content with the proposed change
  88                         $baseRev = Revision::newFromPageId( $page->getId(), $params['baserevid'] );
  89                         if ( !$baseRev ) {
  90                                 $this->dieUsage( "No revision ID {$params['baserevid']}", 'missingrev' );
  91                         }
  92                         $currentRev = $page->getRevision();
  93                         if ( !$currentRev ) {
  94                                 $this->dieUsage( "No current revision of page ID {$page->getId()}", 'missingrev' );
  95                         }
  96                         // Merge in the new version of the section to get the proposed version
  97                         $editContent = $page->replaceSectionAtRev(
  98                                 $params['section'],
  99                                 $textContent,
 100                                 $params['sectiontitle'],
 101                                 $baseRev->getId()
 102                         );
 103                         if ( !$editContent ) {
 104                                 $this->dieUsage( 'Could not merge updated section.', 'replacefailed' );
 105                         }
 106                         if ( $currentRev->getId() == $baseRev->getId() ) {
 107                                 // Base revision was still the latest; nothing to merge
 108                                 $content = $editContent;
 109                         } else {
 110                                 // Merge the edit into the current version
 111                                 $baseContent = $baseRev->getContent();
 112                                 $currentContent = $currentRev->getContent();
 113                                 if ( !$baseContent || !$currentContent ) {
 114                                         $this->dieUsage( "Missing content for page ID {$page->getId()}", 'missingrev' );
 115                                 }
 116                                 $handler = ContentHandler::getForModelID( $baseContent->getModel() );
 117                                 $content = $handler->merge3( $baseContent, $editContent, $currentContent );
 118                         }
 119                 } else {
 120                         // New pages: use the user-provided content model
 121                         $content = $textContent;
 122                 }
 123
 124                 if ( !$content ) { // merge3() failed
 125                         $this->getResult()->addValue( null,
 126                                 $this->getModuleName(), [ 'status' => 'editconflict' ] );
 127                         return;
 128                 }
 129
 130                 // The user will abort the AJAX request by pressing "save", so ignore that
 131                 ignore_user_abort( true );
 132
 133                 if ( $user->pingLimiter( 'stashedit' ) ) {
 134                         $status = 'ratelimited';
 135                 } else {
 136                         $status = self::parseAndStash( $page, $content, $user, $params['summary'] );
 137                         $textKey = $cache->makeKey( 'stashedit', 'text', $textHash );
 138                         $cache->set( $textKey, $text, self::MAX_CACHE_TTL );
 139                 }
 140
 141                 $this->getStats()->increment( "editstash.cache_stores.$status" );
 142
 143                 $this->getResult()->addValue(
 144                         null,
 145                         $this->getModuleName(),
 146                         [
 147                                 'status' => $status,
 148                                 'texthash' => $textHash
 149                         ]
 150                 );
 151         }
 152
 153         /**
 154          * @param WikiPage $page
 155          * @param Content $content Edit content
 156          * @param User $user
 157          * @param string $summary Edit summary
 158          * @return integer ApiStashEdit::ERROR_* constant
 159          * @since 1.25
 160          */
 161         public static function parseAndStash( WikiPage $page, Content $content, User $user, $summary ) {
 162                 $cache = ObjectCache::getLocalClusterInstance();
 163                 $logger = LoggerFactory::getInstance( 'StashEdit' );
 164
 165                 $title = $page->getTitle();
 166                 $key = self::getStashKey( $title, self::getContentHash( $content ), $user );
 167
 168                 // Use the master DB for fast blocking locks
 169                 $dbw = wfGetDB( DB_MASTER );
 170                 if ( !$dbw->lock( $key, __METHOD__, 1 ) ) {
 171                         // De-duplicate requests on the same key
 172                         return self::ERROR_BUSY;
 173                 }
 174                 $unlocker = new ScopedCallback( function () use ( $dbw, $key ) {
 175                         $dbw->unlock( $key, __METHOD__ );
 176                 } );
 177
 178                 $cutoffTime = time() - self::PRESUME_FRESH_TTL_SEC;
 179
 180                 // Reuse any freshly build matching edit stash cache
 181                 $editInfo = $cache->get( $key );
 182                 if ( $editInfo && wfTimestamp( TS_UNIX, $editInfo->timestamp ) >= $cutoffTime ) {
 183                         $alreadyCached = true;
 184                 } else {
 185                         $format = $content->getDefaultFormat();
 186                         $editInfo = $page->prepareContentForEdit( $content, null, $user, $format, false );
 187                         $alreadyCached = false;
 188                 }
 189
 190                 if ( $editInfo && $editInfo->output ) {
 191                         // Let extensions add ParserOutput metadata or warm other caches
 192                         Hooks::run( 'ParserOutputStashForEdit',
 193                                 [ $page, $content, $editInfo->output, $summary, $user ] );
 194
 195                         if ( $alreadyCached ) {
 196                                 $logger->debug( "Already cached parser output for key '$key' ('$title')." );
 197                                 return self::ERROR_NONE;
 198                         }
 199
 200                         list( $stashInfo, $ttl, $code ) = self::buildStashValue(
 201                                 $editInfo->pstContent,
 202                                 $editInfo->output,
 203                                 $editInfo->timestamp,
 204                                 $user
 205                         );
 206
 207                         if ( $stashInfo ) {
 208                                 $ok = $cache->set( $key, $stashInfo, $ttl );
 209                                 if ( $ok ) {
 210                                         $logger->debug( "Cached parser output for key '$key' ('$title')." );
 211                                         return self::ERROR_NONE;
 212                                 } else {
 213                                         $logger->error( "Failed to cache parser output for key '$key' ('$title')." );
 214                                         return self::ERROR_CACHE;
 215                                 }
 216                         } else {
 217                                 $logger->info( "Uncacheable parser output for key '$key' ('$title') [$code]." );
 218                                 return self::ERROR_UNCACHEABLE;
 219                         }
 220                 }
 221
 222                 return self::ERROR_PARSE;
 223         }
 224
 225         /**
 226          * Check that a prepared edit is in cache and still up-to-date
 227          *
 228          * This method blocks if the prepared edit is already being rendered,
 229          * waiting until rendering finishes before doing final validity checks.
 230          *
 231          * The cache is rejected if template or file changes are detected.
 232          * Note that foreign template or file transclusions are not checked.
 233          *
 234          * The result is a map (pstContent,output,timestamp) with fields
 235          * extracted directly from WikiPage::prepareContentForEdit().
 236          *
 237          * @param Title $title
 238          * @param Content $content
 239          * @param User $user User to get parser options from
 240          * @return stdClass|bool Returns false on cache miss
 241          */
 242         public static function checkCache( Title $title, Content $content, User $user ) {
 243                 if ( $user->isBot() ) {
 244                         return false; // bots never stash - don't pollute stats
 245                 }
 246
 247                 $cache = ObjectCache::getLocalClusterInstance();
 248                 $logger = LoggerFactory::getInstance( 'StashEdit' );
 249                 $stats = RequestContext::getMain()->getStats();
 250
 251                 $key = self::getStashKey( $title, self::getContentHash( $content ), $user );
 252                 $editInfo = $cache->get( $key );
 253                 if ( !is_object( $editInfo ) ) {
 254                         $start = microtime( true );
 255                         // We ignore user aborts and keep parsing. Block on any prior parsing
 256                         // so as to use its results and make use of the time spent parsing.
 257                         // Skip this logic if there no master connection in case this method
 258                         // is called on an HTTP GET request for some reason.
 259                         $lb = wfGetLB();
 260                         $dbw = $lb->getAnyOpenConnection( $lb->getWriterIndex() );
 261                         if ( $dbw && $dbw->lock( $key, __METHOD__, 30 ) ) {
 262                                 $editInfo = $cache->get( $key );
 263                                 $dbw->unlock( $key, __METHOD__ );
 264                         }
 265
 266                         $timeMs = 1000 * max( 0, microtime( true ) - $start );
 267                         $stats->timing( 'editstash.lock_wait_time', $timeMs );
 268                 }
 269
 270                 if ( !is_object( $editInfo ) || !$editInfo->output ) {
 271                         $stats->increment( 'editstash.cache_misses.no_stash' );
 272                         $logger->debug( "Empty cache for key '$key' ('$title'); user '{$user->getName()}'." );
 273                         return false;
 274                 }
 275
 276                 $age = time() - wfTimestamp( TS_UNIX, $editInfo->output->getCacheTime() );
 277                 if ( $age <= self::PRESUME_FRESH_TTL_SEC ) {
 278                         // Assume nothing changed in this time
 279                         $stats->increment( 'editstash.cache_hits.presumed_fresh' );
 280                         $logger->debug( "Timestamp-based cache hit for key '$key' (age: $age sec)." );
 281                 } elseif ( isset( $editInfo->edits ) && $editInfo->edits === $user->getEditCount() ) {
 282                         // Logged-in user made no local upload/template edits in the meantime
 283                         $stats->increment( 'editstash.cache_hits.presumed_fresh' );
 284                         $logger->debug( "Edit count based cache hit for key '$key' (age: $age sec)." );
 285                 } elseif ( $user->isAnon()
 286                         && self::lastEditTime( $user ) < $editInfo->output->getCacheTime()
 287                 ) {
 288                         // Logged-out user made no local upload/template edits in the meantime
 289                         $stats->increment( 'editstash.cache_hits.presumed_fresh' );
 290                         $logger->debug( "Edit check based cache hit for key '$key' (age: $age sec)." );
 291                 } else {
 292                         // User may have changed included content
 293                         $editInfo = false;
 294                 }
 295
 296                 if ( !$editInfo ) {
 297                         $stats->increment( 'editstash.cache_misses.proven_stale' );
 298                         $logger->info( "Stale cache for key '$key'; old key with outside edits. (age: $age sec)" );
 299                 } elseif ( $editInfo->output->getFlag( 'vary-revision' ) ) {
 300                         // This can be used for the initial parse, e.g. for filters or doEditContent(),
 301                         // but a second parse will be triggered in doEditUpdates(). This is not optimal.
 302                         $logger->info( "Cache for key '$key' ('$title') has vary_revision." );
 303                 } elseif ( $editInfo->output->getFlag( 'vary-revision-id' ) ) {
 304                         // Similar to the above if we didn't guess the ID correctly.
 305                         $logger->info( "Cache for key '$key' ('$title') has vary_revision_id." );
 306                 }
 307
 308                 return $editInfo;
 309         }
 310
 311         /**
 312          * @param User $user
 313          * @return string|null TS_MW timestamp or null
 314          */
 315         private static function lastEditTime( User $user ) {
 316                 $time = wfGetDB( DB_SLAVE )->selectField(
 317                         'recentchanges',
 318                         'MAX(rc_timestamp)',
 319                         [ 'rc_user_text' => $user->getName() ],
 320                         __METHOD__
 321                 );
 322
 323                 return wfTimestampOrNull( TS_MW, $time );
 324         }
 325
 326         /**
 327          * Get hash of the content, factoring in model/format
 328          *
 329          * @param Content $content
 330          * @return string
 331          */
 332         private static function getContentHash( Content $content ) {
 333                 return sha1( implode( "\n", [
 334                         $content->getModel(),
 335                         $content->getDefaultFormat(),
 336                         $content->serialize( $content->getDefaultFormat() )
 337                 ] ) );
 338         }
 339
 340         /**
 341          * Get the temporary prepared edit stash key for a user
 342          *
 343          * This key can be used for caching prepared edits provided:
 344          *   - a) The $user was used for PST options
 345          *   - b) The parser output was made from the PST using cannonical matching options
 346          *
 347          * @param Title $title
 348          * @param string $contentHash Result of getContentHash()
 349          * @param User $user User to get parser options from
 350          * @return string
 351          */
 352         private static function getStashKey( Title $title, $contentHash, User $user ) {
 353                 return ObjectCache::getLocalClusterInstance()->makeKey(
 354                         'prepared-edit',
 355                         md5( $title->getPrefixedDBkey() ),
 356                         // Account for the edit model/text
 357                         $contentHash,
 358                         // Account for user name related variables like signatures
 359                         md5( $user->getId() . "\n" . $user->getName() )
 360                 );
 361         }
 362
 363         /**
 364          * Build a value to store in memcached based on the PST content and parser output
 365          *
 366          * This makes a simple version of WikiPage::prepareContentForEdit() as stash info
 367          *
 368          * @param Content $pstContent Pre-Save transformed content
 369          * @param ParserOutput $parserOutput
 370          * @param string $timestamp TS_MW
 371          * @param User $user
 372          * @return array (stash info array, TTL in seconds, info code) or (null, 0, info code)
 373          */
 374         private static function buildStashValue(
 375                 Content $pstContent, ParserOutput $parserOutput, $timestamp, User $user
 376         ) {
 377                 // If an item is renewed, mind the cache TTL determined by config and parser functions.
 378                 // Put an upper limit on the TTL for sanity to avoid extreme template/file staleness.
 379                 $since = time() - wfTimestamp( TS_UNIX, $parserOutput->getTimestamp() );
 380                 $ttl = min( $parserOutput->getCacheExpiry() - $since, self::MAX_CACHE_TTL );
 381                 if ( $ttl <= 0 ) {
 382                         return [ null, 0, 'no_ttl' ];
 383                 }
 384
 385                 // Only store what is actually needed
 386                 $stashInfo = (object)[
 387                         'pstContent' => $pstContent,
 388                         'output'     => $parserOutput,
 389                         'timestamp'  => $timestamp,
 390                         'edits'      => $user->getEditCount()
 391                 ];
 392
 393                 return [ $stashInfo, $ttl, 'ok' ];
 394         }
 395
 396         public function getAllowedParams() {
 397                 return [
 398                         'title' => [
 399                                 ApiBase::PARAM_TYPE => 'string',
 400                                 ApiBase::PARAM_REQUIRED => true
 401                         ],
 402                         'section' => [
 403                                 ApiBase::PARAM_TYPE => 'string',
 404                         ],
 405                         'sectiontitle' => [
 406                                 ApiBase::PARAM_TYPE => 'string'
 407                         ],
 408                         'text' => [
 409                                 ApiBase::PARAM_TYPE => 'text',
 410                                 ApiBase::PARAM_DFLT => null
 411                         ],
 412                         'stashedtexthash' => [
 413                                 ApiBase::PARAM_TYPE => 'string',
 414                                 ApiBase::PARAM_DFLT => null
 415                         ],
 416                         'summary' => [
 417                                 ApiBase::PARAM_TYPE => 'string',
 418                         ],
 419                         'contentmodel' => [
 420                                 ApiBase::PARAM_TYPE => ContentHandler::getContentModels(),
 421                                 ApiBase::PARAM_REQUIRED => true
 422                         ],
 423                         'contentformat' => [
 424                                 ApiBase::PARAM_TYPE => ContentHandler::getAllContentFormats(),
 425                                 ApiBase::PARAM_REQUIRED => true
 426                         ],
 427                         'baserevid' => [
 428                                 ApiBase::PARAM_TYPE => 'integer',
 429                                 ApiBase::PARAM_REQUIRED => true
 430                         ]
 431                 ];
 432         }
 433
 434         public function needsToken() {
 435                 return 'csrf';
 436         }
 437
 438         public function mustBePosted() {
 439                 return true;
 440         }
 441
 442         public function isWriteMode() {
 443                 return true;
 444         }
 445
 446         public function isInternal() {
 447                 return true;
 448         }
 449 }