* Job wrapper for HTMLCacheUpdate. Gets run whenever a related
* job gets called from the queue.
*
+ * This class is designed to work efficiently with small numbers of links, and
+ * to work reasonably well with up to ~10^5 links. Above ~10^6 links, the memory
+ * and time requirements of loading all backlinked IDs in doUpdate() might become
+ * prohibitive. The requirements measured at Wikimedia are approximately:
+ *
+ * memory: 48 bytes per row
+ * time: 16us per row for the query plus processing
+ *
+ * The reason this query is done is to support partitioning of the job
+ * by backlinked ID. The memory issue could be allieviated by doing this query in
+ * batches, but of course LIMIT with an offset is inefficient on the DB side.
+ *
+ * The class is nevertheless a vast improvement on the previous method of using
+ * File::getLinksTo() and Title::touchArray(), which uses about 2KB of memory per
+ * link.
+ *
* @ingroup JobQueue
*/
class HTMLCacheUpdateJob extends Job {
- var $table, $start, $end;
+ /** @var BacklinkCache */
+ protected $blCache;
+
+ protected $rowsPerJob, $rowsPerQuery;
/**
* Construct a job
* @param $id Integer: job id
*/
function __construct( $title, $params, $id = 0 ) {
+ global $wgUpdateRowsPerJob, $wgUpdateRowsPerQuery;
+
parent::__construct( 'htmlCacheUpdate', $title, $params, $id );
- $this->table = $params['table'];
- $this->start = $params['start'];
- $this->end = $params['end'];
+
+ $this->rowsPerJob = $wgUpdateRowsPerJob;
+ $this->rowsPerQuery = $wgUpdateRowsPerQuery;
+ $this->blCache = $title->getBacklinkCache();
}
public function run() {
- $update = new HTMLCacheUpdate( $this->title, $this->table, $this->start, $this->end );
- $update->doUpdate();
+ if ( isset( $this->params['start'] ) && isset( $this->params['end'] ) ) {
+ # This is hit when a job is actually performed
+ return $this->doPartialUpdate();
+ } else {
+ # This is hit when the jobs have to be inserted
+ return $this->doFullUpdate();
+ }
+ }
+
+ /**
+ * Update all of the backlinks
+ */
+ protected function doFullUpdate() {
+ # Get an estimate of the number of rows from the BacklinkCache
+ $numRows = $this->blCache->getNumLinks( $this->params['table'] );
+ if ( $numRows > $this->rowsPerJob * 2 ) {
+ # Do fast cached partition
+ $this->insertPartitionJobs();
+ } else {
+ # Get the links from the DB
+ $titleArray = $this->blCache->getLinks( $this->params['table'] );
+ # Check if the row count estimate was correct
+ if ( $titleArray->count() > $this->rowsPerJob * 2 ) {
+ # Not correct, do accurate partition
+ wfDebug( __METHOD__.": row count estimate was incorrect, repartitioning\n" );
+ $this->insertJobsFromTitles( $titleArray );
+ } else {
+ $this->invalidateTitles( $titleArray ); // just do the query
+ }
+ }
+ return true;
+ }
+
+ /**
+ * Update some of the backlinks, defined by a page ID range
+ */
+ protected function doPartialUpdate() {
+ $titleArray = $this->blCache->getLinks(
+ $this->params['table'], $this->params['start'], $this->params['end'] );
+ if ( $titleArray->count() <= $this->rowsPerJob * 2 ) {
+ # This partition is small enough, do the update
+ $this->invalidateTitles( $titleArray );
+ } else {
+ # Partitioning was excessively inaccurate. Divide the job further.
+ # This can occur when a large number of links are added in a short
+ # period of time, say by updating a heavily-used template.
+ $this->insertJobsFromTitles( $titleArray );
+ }
return true;
}
+
+ /**
+ * Partition the current range given by $this->params['start'] and $this->params['end'],
+ * using a pre-calculated title array which gives the links in that range.
+ * Queue the resulting jobs.
+ *
+ * @param $titleArray array
+ * @param $rootJobParams array
+ * @rerturn void
+ */
+ protected function insertJobsFromTitles( $titleArray, $rootJobParams = array() ) {
+ // Carry over any "root job" information
+ $rootJobParams = $this->getRootJobParams();
+ # We make subpartitions in the sense that the start of the first job
+ # will be the start of the parent partition, and the end of the last
+ # job will be the end of the parent partition.
+ $jobs = array();
+ $start = $this->params['start']; # start of the current job
+ $numTitles = 0;
+ foreach ( $titleArray as $title ) {
+ $id = $title->getArticleID();
+ # $numTitles is now the number of titles in the current job not
+ # including the current ID
+ if ( $numTitles >= $this->rowsPerJob ) {
+ # Add a job up to but not including the current ID
+ $jobs[] = new HTMLCacheUpdateJob( $this->title,
+ array(
+ 'table' => $this->params['table'],
+ 'start' => $start,
+ 'end' => $id - 1
+ ) + $rootJobParams // carry over information for de-duplication
+ );
+ $start = $id;
+ $numTitles = 0;
+ }
+ $numTitles++;
+ }
+ # Last job
+ $jobs[] = new HTMLCacheUpdateJob( $this->title,
+ array(
+ 'table' => $this->params['table'],
+ 'start' => $start,
+ 'end' => $this->params['end']
+ ) + $rootJobParams // carry over information for de-duplication
+ );
+ wfDebug( __METHOD__.": repartitioning into " . count( $jobs ) . " jobs\n" );
+
+ if ( count( $jobs ) < 2 ) {
+ # I don't think this is possible at present, but handling this case
+ # makes the code a bit more robust against future code updates and
+ # avoids a potential infinite loop of repartitioning
+ wfDebug( __METHOD__.": repartitioning failed!\n" );
+ $this->invalidateTitles( $titleArray );
+ } else {
+ JobQueueGroup::singleton()->push( $jobs );
+ }
+ }
+
+ /**
+ * @param $rootJobParams array
+ * @return void
+ */
+ protected function insertPartitionJobs( $rootJobParams = array() ) {
+ // Carry over any "root job" information
+ $rootJobParams = $this->getRootJobParams();
+
+ $batches = $this->blCache->partition( $this->params['table'], $this->rowsPerJob );
+ if ( !count( $batches ) ) {
+ return; // no jobs to insert
+ }
+
+ $jobs = array();
+ foreach ( $batches as $batch ) {
+ list( $start, $end ) = $batch;
+ $jobs[] = new HTMLCacheUpdateJob( $this->title,
+ array(
+ 'table' => $this->params['table'],
+ 'start' => $start,
+ 'end' => $end,
+ ) + $rootJobParams // carry over information for de-duplication
+ );
+ }
+
+ JobQueueGroup::singleton()->push( $jobs );
+ }
+
+ /**
+ * Invalidate an array (or iterator) of Title objects, right now
+ * @param $titleArray array
+ */
+ protected function invalidateTitles( $titleArray ) {
+ global $wgUseFileCache, $wgUseSquid;
+
+ $dbw = wfGetDB( DB_MASTER );
+ $timestamp = $dbw->timestamp();
+
+ # Get all IDs in this query into an array
+ $ids = array();
+ foreach ( $titleArray as $title ) {
+ $ids[] = $title->getArticleID();
+ }
+
+ if ( !$ids ) {
+ return;
+ }
+
+ # Don't invalidated pages that were already invalidated
+ $touchedCond = isset( $this->params['rootJobTimestamp'] )
+ ? array( "page_touched < " .
+ $dbw->addQuotes( $dbw->timestamp( $this->params['rootJobTimestamp'] ) ) )
+ : array();
+
+ # Update page_touched
+ $batches = array_chunk( $ids, $this->rowsPerQuery );
+ foreach ( $batches as $batch ) {
+ $dbw->update( 'page',
+ array( 'page_touched' => $timestamp ),
+ array( 'page_id' => $batch ) + $touchedCond,
+ __METHOD__
+ );
+ }
+
+ # Update squid
+ if ( $wgUseSquid ) {
+ $u = SquidUpdate::newFromTitles( $titleArray );
+ $u->doUpdate();
+ }
+
+ # Update file cache
+ if ( $wgUseFileCache ) {
+ foreach ( $titleArray as $title ) {
+ HTMLFileCache::clearFileCache( $title );
+ }
+ }
+ }
}
dépôts / lhc / web / wiklou.git / blobdiff