jenkins-bot has submitted this change and it was merged. (
https://gerrit.wikimedia.org/r/395690 )
Change subject: objectcache: add another example case to
WANObjectCache::getWithSetCallback()
......................................................................
objectcache: add another example case to WANObjectCache::getWithSetCallback()
Change-Id: I4beb1441790f5371d9fe55ca05cd17dc9fcdcf80
---
M includes/libs/objectcache/WANObjectCache.php
1 file changed, 35 insertions(+), 1 deletion(-)
Approvals:
Krinkle: Looks good to me, approved
jenkins-bot: Verified
diff --git a/includes/libs/objectcache/WANObjectCache.php
b/includes/libs/objectcache/WANObjectCache.php
index ac28076..36b45a1 100644
--- a/includes/libs/objectcache/WANObjectCache.php
+++ b/includes/libs/objectcache/WANObjectCache.php
@@ -900,6 +900,40 @@
* );
* @endcode
*
+ * Example usage (key holding an LRU subkey:value map; this can avoid
flooding cache with
+ * keys for an unlimited set of (constraint,situation) pairs, thereby
avoiding elevated
+ * cache evictions and wasted memory):
+ * @code
+ * $catSituationTolerabilityCache =
$this->cache->getWithSetCallback(
+ * // Group by constraint ID/hash, cat family ID/hash, or
something else useful
+ * $this->cache->makeKey( 'cat-situation-tolerablity-checks',
$groupKey ),
+ * WANObjectCache::TTL_DAY, // rarely used groups should fade
away
+ * // The $scenarioKey format is $constraintId:<ID/hash of
$situation>
+ * function ( $cacheMap ) use ( $scenarioKey, $constraintId,
$situation ) {
+ * $lruCache = MapCacheLRU::newFromArray( $cacheMap ?: [],
self::CACHE_SIZE );
+ * $result = $lruCache->get( $scenarioKey ); // triggers
LRU bump if present
+ * if ( $result === null || $this->isScenarioResultExpired(
$result ) ) {
+ * $result = $this->checkScenarioTolerability(
$constraintId, $situation );
+ * $lruCache->set( $scenarioKey, $result, 3 / 8 );
+ * }
+ * // Save the new LRU cache map and reset the map's TTL
+ * return $lruCache->toArray();
+ * },
+ * [
+ * // Once map is > 1 sec old, consider refreshing
+ * 'ageNew' => 1,
+ * // Update within 5 seconds after "ageNew" given a 1hz
cache check rate
+ * 'hotTTR' => 5,
+ * // Avoid querying cache servers multiple times in a
request; this also means
+ * // that a request can only alter the value of any given
constraint key once
+ * 'pcTTL' => WANObjectCache::TTL_PROC_LONG
+ * ]
+ * );
+ * $tolerability = isset(
$catSituationTolerabilityCache[$scenarioKey] )
+ * ? $catSituationTolerabilityCache[$scenarioKey]
+ * : $this->checkScenarioTolerability( $constraintId,
$situation );
+ * @endcode
+ *
* @see WANObjectCache::get()
* @see WANObjectCache::set()
*
@@ -1678,7 +1712,7 @@
* $ttl = ( $newList === $oldValue )
* // No change: cache for 150% of the age of
$oldValue
* ? $cache->adaptiveTTL( $oldAsOf, $maxTTL,
$minTTL, 1.5 )
- * // Changed: cache for %50 of the age of $oldValue
+ * // Changed: cache for 50% of the age of $oldValue
* : $cache->adaptiveTTL( $oldAsOf, $maxTTL,
$minTTL, .5 );
* }
*
--
To view, visit https://gerrit.wikimedia.org/r/395690
To unsubscribe, visit https://gerrit.wikimedia.org/r/settings
Gerrit-MessageType: merged
Gerrit-Change-Id: I4beb1441790f5371d9fe55ca05cd17dc9fcdcf80
Gerrit-PatchSet: 5
Gerrit-Project: mediawiki/core
Gerrit-Branch: master
Gerrit-Owner: Aaron Schulz <[email protected]>
Gerrit-Reviewer: Krinkle <[email protected]>
Gerrit-Reviewer: jenkins-bot <>
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