Simplify ApiStashEdit::checkCache()

Per https://grafana.wikimedia.org/dashboard/db/edit-stash, the
proven_* cases are almost never hit. Simplify the code to avoid
complexity and slow link table queries.

Change-Id: I3f8bd79a80ddb26c6188b1a301c08766e38f6ad4

diff --git a/includes/api/ApiStashEdit.php b/includes/api/ApiStashEdit.php
index 51da606..814a111 100644 (file)
--- a/includes/api/ApiStashEdit.php
+++ b/includes/api/ApiStashEdit.php
@@ -41,6 +41,7 @@ class ApiStashEdit extends ApiBase {
        const ERROR_UNCACHEABLE = 'uncacheable';
 
        const PRESUME_FRESH_TTL_SEC = 30;
+       const MAX_CACHE_TTL = 300; // 5 minutes
 
        public function execute() {
                $user = $this->getUser();
@@ -319,64 +320,10 @@ class ApiStashEdit extends ApiBase {
                        return $editInfo;
                }
 
-               $dbr = wfGetDB( DB_SLAVE );
+               $stats->increment( 'editstash.cache_misses.proven_stale' );
+               $logger->info( "Stale cache for key '$key'; old key with outside edits. (age: $age sec)" );
 
-               $templates = []; // conditions to find changes/creations
-               $templateUses = 0; // expected existing templates
-               foreach ( $editInfo->output->getTemplateIds() as $ns => $stuff ) {
-                       foreach ( $stuff as $dbkey => $revId ) {
-                               $templates[(string)$ns][$dbkey] = (int)$revId;
-                               ++$templateUses;
-                       }
-               }
-               // Check that no templates used in the output changed...
-               if ( count( $templates ) ) {
-                       $res = $dbr->select(
-                               'page',
-                               [ 'ns' => 'page_namespace', 'dbk' => 'page_title', 'page_latest' ],
-                               $dbr->makeWhereFrom2d( $templates, 'page_namespace', 'page_title' ),
-                               __METHOD__
-                       );
-                       $changed = false;
-                       foreach ( $res as $row ) {
-                               $changed = $changed || ( $row->page_latest != $templates[$row->ns][$row->dbk] );
-                       }
-
-                       if ( $changed || $res->numRows() != $templateUses ) {
-                               $stats->increment( 'editstash.cache_misses.proven_stale' );
-                               $logger->info( "Stale cache for key '$key'; template changed. (age: $age sec)" );
-                               return false;
-                       }
-               }
-
-               $files = []; // conditions to find changes/creations
-               foreach ( $editInfo->output->getFileSearchOptions() as $name => $options ) {
-                       $files[$name] = (string)$options['sha1'];
-               }
-               // Check that no files used in the output changed...
-               if ( count( $files ) ) {
-                       $res = $dbr->select(
-                               'image',
-                               [ 'name' => 'img_name', 'img_sha1' ],
-                               [ 'img_name' => array_keys( $files ) ],
-                               __METHOD__
-                       );
-                       $changed = false;
-                       foreach ( $res as $row ) {
-                               $changed = $changed || ( $row->img_sha1 != $files[$row->name] );
-                       }
-
-                       if ( $changed || $res->numRows() != count( $files ) ) {
-                               $stats->increment( 'editstash.cache_misses.proven_stale' );
-                               $logger->info( "Stale cache for key '$key'; file changed. (age: $age sec)" );
-                               return false;
-                       }
-               }
-
-               $stats->increment( 'editstash.cache_hits.proven_fresh' );
-               $logger->debug( "Verified cache hit for key '$key' (age: $age sec)." );
-
-               return $editInfo;
+               return false;
        }
 
        /**
@@ -437,7 +384,7 @@ class ApiStashEdit extends ApiBase {
                // If an item is renewed, mind the cache TTL determined by config and parser functions.
                // Put an upper limit on the TTL for sanity to avoid extreme template/file staleness.
                $since = time() - wfTimestamp( TS_UNIX, $parserOutput->getTimestamp() );
-               $ttl = min( $parserOutput->getCacheExpiry() - $since, 5 * 60 );
+               $ttl = min( $parserOutput->getCacheExpiry() - $since, self::MAX_CACHE_TTL );
 
                if ( $ttl > 0 && !$parserOutput->getFlag( 'vary-revision' ) ) {
                        // Only store what is actually needed