added metrics interface

Author: wolfy-j

src/Metrics.php

@@ -16,7 +16,7 @@
 /**
  * Application metrics.
  */
-final class Metrics
+final class Metrics implements MetricsInterface
 {
     /** @var RPC */
     private $rpc;

src/MetricsInterface.php

@@ -0,0 +1,59 @@
+<?php
+/**
+ * Spiral Framework.
+ *
+ * @license   MIT
+ * @author    Anton Titov (Wolfy-J)
+ */
+declare(strict_types=1);
+
+namespace Spiral\RoadRunner;
+
+use Spiral\RoadRunner\Exception\MetricException;
+
+interface MetricsInterface
+{
+    /**
+     * Add collector value. Fallback to appropriate method of related collector.
+     *
+     * @param string $collector
+     * @param float  $value
+     * @param array  $labels
+     *
+     * @throws MetricException
+     */
+    public function add(string $collector, float $value, array $labels = []);
+
+    /**
+     * Subtract the collector value, only for gauge collector.
+     *
+     * @param string $collector
+     * @param float  $value
+     * @param array  $labels
+     *
+     * @throws MetricException
+     */
+    public function sub(string $collector, float $value, array $labels = []);
+
+    /**
+     * Observe collector value, only for histogram and summary collectors.
+     *
+     * @param string $collector
+     * @param float  $value
+     * @param array  $labels
+     *
+     * @throws MetricException
+     */
+    public function observe(string $collector, float $value, array $labels = []);
+
+    /**
+     * Set collector value, only for gauge collector.
+     *
+     * @param string $collector
+     * @param float  $value
+     * @param array  $labels
+     *
+     * @throws MetricException
+     */
+    public function set(string $collector, float $value, array $labels = []);
+}