MediaWiki  master
purgeParserCache.php
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1 <?php
25 require_once __DIR__ . '/Maintenance.php';
26 
29 use Wikimedia\Timestamp\ConvertibleTimestamp;
30 
37 
39  private $lastProgress;
40 
42  private $lastTimestamp;
43 
44  private $tmpCount = 0;
45  private $usleep = 0;
46 
47  public function __construct() {
48  parent::__construct();
49  $this->addDescription( "Remove old objects from the parser cache. " .
50  "This only works when the parser cache is in an SQL database." );
51  $this->addOption( 'expiredate', 'Delete objects expiring before this date.', false, true );
52  $this->addOption(
53  'age',
54  'Delete objects created more than this many seconds ago, assuming ' .
55  '$wgParserCacheExpireTime has remained consistent.',
56  false,
57  true );
58  $this->addOption( 'dry-run', 'Perform a dry run, to verify age and date calculation.' );
59  $this->addOption( 'msleep', 'Milliseconds to sleep between purge chunks of $wgUpdateRowsPerQuery.',
60  false,
61  true );
62  $this->addOption(
63  'tag',
64  'Purge a single server only. This feature is designed for use by large wiki farms where ' .
65  'one has to purge multiple servers concurrently in order to keep up with new writes. ' .
66  'This requires using the SqlBagOStuff "servers" option in $wgObjectCaches.',
67  false,
68  true );
69  }
70 
71  public function execute() {
72  $inputDate = $this->getOption( 'expiredate' );
73  $inputAge = $this->getOption( 'age' );
74 
75  if ( $inputDate !== null ) {
76  $timestamp = strtotime( $inputDate );
77  } elseif ( $inputAge !== null ) {
78  $expireTime = (int)$this->getConfig()->get( MainConfigNames::ParserCacheExpireTime );
79  $timestamp = time() + $expireTime - intval( $inputAge );
80  } else {
81  $this->fatalError( "Must specify either --expiredate or --age" );
82  }
83  $this->usleep = 1e3 * $this->getOption( 'msleep', 0 );
84  $this->lastTimestamp = microtime( true );
85 
86  $humanDate = ConvertibleTimestamp::convert( TS_RFC2822, $timestamp );
87  if ( $this->hasOption( 'dry-run' ) ) {
88  $this->fatalError( "\nDry run mode, would delete objects having an expiry before " . $humanDate . "\n" );
89  }
90 
91  $this->output( "Deleting objects expiring before " . $humanDate . "\n" );
92 
93  $pc = MediaWikiServices::getInstance()->getParserCache()->getCacheStorage();
94  $success = $pc->deleteObjectsExpiringBefore(
95  $timestamp,
96  [ $this, 'showProgressAndWait' ],
97  INF,
98  // Note that "0" can be a valid server tag, and must not be discarded or changed to null.
99  $this->getOption( 'tag', null )
100  );
101  if ( !$success ) {
102  $this->fatalError( "\nCannot purge this kind of parser cache." );
103  }
104  $this->showProgressAndWait( 100 );
105  $this->output( "\nDone\n" );
106  }
107 
108  public function showProgressAndWait( $percent ) {
109  // Parser caches involve mostly-unthrottled writes of large blobs. This is sometimes prone
110  // to replication lag. As such, while our purge queries are simple primary key deletes,
111  // we want to avoid adding significant load to the replication stream, by being
112  // proactively graceful with these sleeps between each batch.
113  // The reason we don't explicitly wait for replication is that that would require the script
114  // to be aware of cross-dc replicas, which we prefer not to, and waiting for replication
115  // and confirmation latency might actually be *too* graceful and take so long that the
116  // purge script would not be able to finish within 24 hours for large wiki farms.
117  // (T150124).
118  usleep( $this->usleep );
119  $this->tmpCount++;
120 
121  $percentString = sprintf( "%.1f", $percent );
122  if ( $percentString === $this->lastProgress ) {
123  // Only print a line if we've progressed >= 0.1% since the last printed line.
124  // This does not mean every 0.1% step is printed since we only run this callback
125  // once after a deletion batch. How often and how many lines we print depends on the
126  // batch size (SqlBagOStuff::deleteObjectsExpiringBefore, $wgUpdateRowsPerQuery),
127  // and on how many table rows there are.
128  return;
129  }
130  $now = microtime( true );
131  $sec = sprintf( "%.1f", $now - $this->lastTimestamp );
132 
133  // Give a sense of how much time is spent in the delete operations vs the sleep time,
134  // by recording the number of iterations we've completed since the last progress update.
135  $this->output( "... {$percentString}% done (+{$this->tmpCount} iterations in {$sec}s)\n" );
136 
137  $this->lastProgress = $percentString;
138  $this->tmpCount = 0;
139  $this->lastTimestamp = $now;
140  }
141 }
142 
143 $maintClass = PurgeParserCache::class;
144 require_once RUN_MAINTENANCE_IF_MAIN;
$success
Abstract maintenance class for quickly writing and churning out maintenance scripts with minimal effo...
Definition: Maintenance.php:66
output( $out, $channel=null)
Throw some output to the user.
hasOption( $name)
Checks to see if a particular option was set.
addDescription( $text)
Set the description text.
addOption( $name, $description, $required=false, $withArg=false, $shortName=false, $multiOccurrence=false)
Add a parameter to the script.
getOption( $name, $default=null)
Get an option, or return the default.
fatalError( $msg, $exitCode=1)
Output a message and terminate the current script.
A class containing constants representing the names of configuration variables.
Service locator for MediaWiki core services.
Maintenance script to remove old objects from the parser cache.
execute()
Do the actual work.
__construct()
Default constructor.
showProgressAndWait( $percent)