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<?php
/**
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
*/
declare( strict_types=1 );
namespace Wikimedia\Stats;
use TypeError;
use Wikimedia\Stats\Metrics\MetricInterface;
use Wikimedia\Stats\Metrics\NullMetric;
/**
* Singleton cache for Metric instances.
*
* For reuse and collision avoidance. Serves as the data source for Metric Emitters.
*
* @author Cole White
* @since 1.41
*/
class StatsCache {
public const DELIMITER = '.';
/** @var MetricInterface[] */
private array $cache = [];
/**
* Get a metric object from cache or null.
*
* @param string $component
* @param string $name
* @param string $expectedClass
* @return MetricInterface|null
* @throws TypeError If cached value is for a different metric type.
*/
public function get( string $component, string $name, string $expectedClass ) {
$key = self::cacheKey( $component, $name );
$metric = $this->cache[$key] ?? null;
if ( $metric !== null && get_class( $metric ) !== $expectedClass ) {
throw new TypeError( "Encountered metric name collision: $key defined as "
. get_class( $metric ) . " but $expectedClass was requested" );
}
return $metric;
}
/**
* Add a metric object to the cache.
*
* @param string $component
* @param string $name
* @param MetricInterface|NullMetric $metric
*/
public function set( string $component, string $name, $metric ): void {
$this->cache[self::cacheKey( $component, $name )] = $metric;
}
/**
* Get all metrics from cache.
*
* @return MetricInterface[]
*/
public function getAllMetrics(): array {
return $this->cache;
}
/**
* Clears the cache.
*
* @return void
*/
public function clear(): void {
$this->cache = [];
}
/**
* Get the metric formatted name.
*
* Takes the provided name and constructs a more specific name by combining
* component and name.
*
* @param string $component
* @param string $name
* @return string
*/
private static function cacheKey( string $component, string $name ): string {
// mitigate collision of empty-component metric with a component metric
if ( $component !== '' ) {
return implode( self::DELIMITER, [ $component, $name ] );
}
return $name;
}
}
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