/**
* Retrieve or build a graph cache bucket from the cache.
*
* Normally, this operates as a readthrough cache call. It can also be used
* to force a cache update by passing the existing data to `$rebuild_data`.
*
* @param int Bucket key, from @{method:getBucketKey}.
* @param mixed Current data, to force a cache rebuild of this bucket.
* @return array Data from the cache.
* @task cache
*/
private function getBucketData($bucket_key, $rebuild_data = null)
{
$cache_key = $this->getBucketCacheKey($bucket_key);
// TODO: This cache stuff could be handled more gracefully, but the
// database cache currently requires values to be strings and needs
// some tweaking to support this as part of a stack. Our cache semantics
// here are also unusual (not purely readthrough) because this cache is
// appendable.
$cache_level1 = PhabricatorCaches::getRepositoryGraphL1Cache();
$cache_level2 = PhabricatorCaches::getRepositoryGraphL2Cache();
if ($rebuild_data === null) {
$bucket_data = $cache_level1->getKey($cache_key);
if ($bucket_data) {
return $bucket_data;
}
$bucket_data = $cache_level2->getKey($cache_key);
if ($bucket_data) {
$unserialized = @unserialize($bucket_data);
if ($unserialized) {
// Fill APC if we got a database hit but missed in APC.
$cache_level1->setKey($cache_key, $unserialized);
return $unserialized;
}
}
}
if (!is_array($rebuild_data)) {
$rebuild_data = array();
}
$bucket_data = $this->rebuildBucket($bucket_key, $rebuild_data);
// Don't bother writing the data if we didn't update anything.
if ($bucket_data !== $rebuild_data) {
$cache_level2->setKey($cache_key, serialize($bucket_data));
$cache_level1->setKey($cache_key, $bucket_data);
}
return $bucket_data;
}