Removed "page-lastedit" cache key trick from WikiPage

* Just rely on chronology protected and edit conflict handling.
  The time a user spends looking at and editing pages is larger
  than any normal slave lag anyway.
* However make sure that pages just made in the request are visible.
* In "master" datacenters, the slave lag will low anyway, and
  callers make use of $flags when needed. In other datacenters,
  the cache will itself be subject to lag anyway.
* Logging (DBPerformance log) shows this case is very rarely
  hit anyway.

Change-Id: If34d67c02f9a7bf0a506ee8f3990697eb403a710

diff --git a/includes/page/WikiPage.php b/includes/page/WikiPage.php
index d96e271..f2a3c79 100644 (file)
--- a/includes/page/WikiPage.php
+++ b/includes/page/WikiPage.php
@@ -367,14 +367,12 @@ class WikiPage implements Page, IDBAccessObject {
                        $data = $this->pageDataFromTitle( wfGetDB( DB_MASTER ), $this->mTitle );
                } elseif ( $from === self::READ_NORMAL ) {
                        $data = $this->pageDataFromTitle( wfGetDB( DB_SLAVE ), $this->mTitle );
-                       // Use a "last rev inserted" timestamp key to diminish the issue of slave lag.
-                       // Note that DB also stores the master position in the session and checks it.
-                       $touched = $this->getCachedLastEditTime();
-                       if ( $touched ) { // key set
-                               if ( !$data || $touched > wfTimestamp( TS_MW, $data->page_touched ) ) {
-                                       $from = self::READ_LATEST;
-                                       $data = $this->pageDataFromTitle( wfGetDB( DB_MASTER ), $this->mTitle );
-                               }
+                       if ( !$data
+                               && wfGetLB()->getServerCount() > 1
+                               && wfGetLB()->hasOrMadeRecentMasterChanges()
+                       ) {
+                               $from = self::READ_LATEST;
+                               $data = $this->pageDataFromTitle( wfGetDB( DB_MASTER ), $this->mTitle );
                        }
                } else {
                        // No idea from where the caller got this data, assume slave database.
@@ -810,29 +808,6 @@ class WikiPage implements Page, IDBAccessObject {
                }
        }
 
-       /**
-        * Get the cached timestamp for the last time the page changed.
-        * This is only used to help handle slave lag by comparing to page_touched.
-        * @return string MW timestamp
-        */
-       protected function getCachedLastEditTime() {
-               global $wgMemc;
-               $key = wfMemcKey( 'page-lastedit', md5( $this->mTitle->getPrefixedDBkey() ) );
-               return $wgMemc->get( $key );
-       }
-
-       /**
-        * Set the cached timestamp for the last time the page changed.
-        * This is only used to help handle slave lag by comparing to page_touched.
-        * @param string $timestamp
-        * @return void
-        */
-       public function setCachedLastEditTime( $timestamp ) {
-               global $wgMemc;
-               $key = wfMemcKey( 'page-lastedit', md5( $this->mTitle->getPrefixedDBkey() ) );
-               $wgMemc->set( $key, wfTimestamp( TS_MW, $timestamp ), 60 * 15 );
-       }
-
        /**
         * Determine whether a page would be suitable for being counted as an
         * article in the site_stats table based on the title & its content
@@ -1304,7 +1279,6 @@ class WikiPage implements Page, IDBAccessObject {
                if ( $result ) {
                        $this->updateRedirectOn( $dbw, $rt, $lastRevIsRedirect );
                        $this->setLastEdit( $revision );
-                       $this->setCachedLastEditTime( $now );
                        $this->mLatest = $revision->getId();
                        $this->mIsRedirect = (bool)$rt;
                        // Update the LinkCache.