From: Aaron Schulz <aschulz@wikimedia.org>
Date: Tue, 26 Mar 2019 05:26:13 +0000 (-0700)
Subject: Prune old edit stash entries from users as they create more
X-Git-Tag: 1.34.0-rc.0~2333^2
X-Git-Url: http://git.cyclocoop.org/%7B%24www_url%7Dadmin/compta/categories//%22?a=commitdiff_plain;h=c3348833097788dd8600e7e8cf826b217245633c;p=lhc%2Fweb%2Fwiklou.git

Prune old edit stash entries from users as they create more

This should reduce pressure on certain medium-large sized memcached
slabs. Pre-1.5 memcached versions have a harder time pruning expired
entries in time to avoid evictions, so it will be most useful that
scenario.

Bug: T203786
Change-Id: Ic357dbfcd9abd525b02e8d631d1344db3745d24c
---

diff --git a/includes/api/ApiStashEdit.php b/includes/api/ApiStashEdit.php
index 455ff458f1..fe5f6c4a44 100644
--- a/includes/api/ApiStashEdit.php
+++ b/includes/api/ApiStashEdit.php
@@ -46,6 +46,8 @@ class ApiStashEdit extends ApiBase {
 	const MAX_CACHE_TTL = 300; // 5 minutes
 	const MAX_SIGNATURE_TTL = 60;
 
+	const MAX_CACHE_RECENT = 2;
+
 	public function execute() {
 		$user = $this->getUser();
 		$params = $this->extractRequestParams();
@@ -461,9 +463,32 @@ class ApiStashEdit extends ApiBase {
 			);
 		}
 
+		if ( $ok ) {
+			// These blobs can waste slots in low cardinality memcached slabs
+			self::pruneExcessStashedEntries( $cache, $user, $key );
+		}
+
 		return $ok ? true : 'store_error';
 	}
 
+	/**
+	 * @param BagOStuff $cache
+	 * @param User $user
+	 * @param string $newKey
+	 */
+	private static function pruneExcessStashedEntries( BagOStuff $cache, User $user, $newKey ) {
+		$key = $cache->makeKey( 'stash-edit-recent', $user->getId() );
+
+		$keyList = $cache->get( $key ) ?: [];
+		if ( count( $keyList ) >= self::MAX_CACHE_RECENT ) {
+			$oldestKey = array_shift( $keyList );
+			$cache->delete( $oldestKey );
+		}
+
+		$keyList[] = $newKey;
+		$cache->set( $key, $keyList, 2 * self::MAX_CACHE_TTL );
+	}
+
 	public function getAllowedParams() {
 		return [
 			'title' => [