BagOStuff: Optionally log duplicate key lookups

[lhc/web/wiklou.git] / includes / libs / objectcache / BagOStuff.php

diff --git a/includes/libs/objectcache/BagOStuff.php b/includes/libs/objectcache/BagOStuff.php
index 1aed280..8e3c0a5 100644 (file)
--- a/includes/libs/objectcache/BagOStuff.php
+++ b/includes/libs/objectcache/BagOStuff.php
@@ -55,9 +55,21 @@ abstract class BagOStuff implements IExpiringStore, LoggerAwareInterface {
        /** @var LoggerInterface */
        protected $logger;
 
+       /** @var callback|null */
+       protected $asyncHandler;
+
        /** @var bool */
        private $debugMode = false;
 
+       /** @var array */
+       private $duplicateKeyLookups = [];
+
+       /** @var bool */
+       private $reportDupes = false;
+
+       /** @var bool */
+       private $dupeTrackScheduled = false;
+
        /** Possible values for getLastError() */
        const ERR_NONE = 0; // no error
        const ERR_NO_RESPONSE = 1; // no response
@@ -71,6 +83,16 @@ abstract class BagOStuff implements IExpiringStore, LoggerAwareInterface {
        const WRITE_SYNC = 1; // synchronously write to all locations for replicated stores
        const WRITE_CACHE_ONLY = 2; // Only change state of the in-memory cache
 
+       /**
+        * $params include:
+        *   - logger: Psr\Log\LoggerInterface instance
+        *   - keyspace: Default keyspace for $this->makeKey()
+        *   - asyncHandler: Callable to use for scheduling tasks after the web request ends.
+        *      In CLI mode, it should run the task immediately.
+        *   - reportDupes: Whether to emit warning log messages for all keys that were
+        *      requested more than once (requires an asyncHandler).
+        * @param array $params
+        */
        public function __construct( array $params = [] ) {
                if ( isset( $params['logger'] ) ) {
                        $this->setLogger( $params['logger'] );
@@ -81,6 +103,14 @@ abstract class BagOStuff implements IExpiringStore, LoggerAwareInterface {
                if ( isset( $params['keyspace'] ) ) {
                        $this->keyspace = $params['keyspace'];
                }
+
+               $this->asyncHandler = isset( $params['asyncHandler'] )
+                       ? $params['asyncHandler']
+                       : null;
+
+               if ( !empty( $params['reportDupes'] ) && is_callable( $this->asyncHandler ) ) {
+                       $this->reportDupes = true;
+               }
        }
 
        /**
@@ -144,9 +174,44 @@ abstract class BagOStuff implements IExpiringStore, LoggerAwareInterface {
                // B/C for ( $key, &$casToken = null, $flags = 0 )
                $flags = is_int( $oldFlags ) ? $oldFlags : $flags;
 
+               $this->trackDuplicateKeys( $key );
+
                return $this->doGet( $key, $flags );
        }
 
+       /**
+        * Track the number of times that a given key has been used.
+        * @param string $key
+        */
+       private function trackDuplicateKeys( $key ) {
+               if ( !$this->reportDupes ) {
+                       return;
+               }
+
+               if ( !isset( $this->duplicateKeyLookups[$key] ) ) {
+                       // Track that we have seen this key. This N-1 counting style allows
+                       // easy filtering with array_filter() later.
+                       $this->duplicateKeyLookups[$key] = 0;
+               } else {
+                       $this->duplicateKeyLookups[$key] += 1;
+
+                       if ( $this->dupeTrackScheduled === false ) {
+                               $this->dupeTrackScheduled = true;
+                               // Schedule a callback that logs keys processed more than once by get().
+                               call_user_func( $this->asyncHandler, function () {
+                                       $dups = array_filter( $this->duplicateKeyLookups );
+                                       foreach ( $dups as $key => $count ) {
+                                               $this->logger->warning(
+                                                       'Duplicate get(): "{key}" fetched {count} times',
+                                                       // Count is N-1 of the actual lookup count
+                                                       [ 'key' => $key, 'count' => $count + 1, ]
+                                               );
+                                       }
+                               } );
+                       }
+               }
+       }
+
        /**
         * @param string $key
         * @param integer $flags Bitfield of BagOStuff::READ_* constants [optional]