fix(fetcher): ignore metric existing in storage, but missed in registry

Author: zlodes

src/Fetcher/StoredMetricsFetcher.php

@@ -5,6 +5,7 @@
 namespace Zlodes\PrometheusClient\Fetcher;
 
 use Generator;
+use Zlodes\PrometheusClient\Exception\MetricNotFoundException;
 use Zlodes\PrometheusClient\Fetcher\DTO\FetchedMetric;
 use Zlodes\PrometheusClient\Metric\Counter;
 use Zlodes\PrometheusClient\Metric\Gauge;
@@ -58,12 +59,16 @@ private function fetchCounters(): Generator
         }
 
         foreach ($countersByName as $metricName => $values) {
-            $metric = $this->registry->getMetric($metricName, Counter::class);
+            try {
+                $metric = $this->registry->getMetric($metricName, Counter::class);
 
-            yield new FetchedMetric(
-                $metric,
-                $values
-            );
+                yield new FetchedMetric(
+                    $metric,
+                    $values
+                );
+            } catch (MetricNotFoundException) {
+                // Skip. Metric might be removed from the registry after using
+            }
         }
     }
 

tests/Fetcher/StoredMetricsFetcherTest.php

@@ -7,6 +7,8 @@
 use Generator;
 use Mockery;
 use PHPUnit\Framework\TestCase;
+use Psr\Log\NullLogger;
+use Zlodes\PrometheusClient\Collector\ByType\CounterCollector;
 use Zlodes\PrometheusClient\Fetcher\DTO\FetchedMetric;
 use Zlodes\PrometheusClient\Fetcher\StoredMetricsFetcher;
 use Zlodes\PrometheusClient\Metric\Counter;
@@ -22,6 +24,10 @@
 use Zlodes\PrometheusClient\Storage\DTO\MetricNameWithLabels;
 use Zlodes\PrometheusClient\Storage\DTO\MetricValue;
 use Zlodes\PrometheusClient\Storage\DTO\SummaryMetricValue;
+use Zlodes\PrometheusClient\Storage\InMemory\InMemoryCounterStorage;
+use Zlodes\PrometheusClient\Tests\Stubs\GaugeStorageStub;
+use Zlodes\PrometheusClient\Tests\Stubs\HistogramStorageStub;
+use Zlodes\PrometheusClient\Tests\Stubs\SummaryStorageStub;
 
 /**
  * Kinda stupid test to check that the fetcher return metric as expected: with correct values and order
@@ -108,7 +114,7 @@ public function testFetch(): void
 
         $summaryStorageMock
             ->expects('fetchSummaries')
-            ->andReturnUsing(static function(): Generator {
+            ->andReturnUsing(static function (): Generator {
                 yield new SummaryMetricValue(
                     new MetricNameWithLabels('memory_usage'),
                     [300, 500, 200, 500, 400]
@@ -245,4 +251,34 @@ public function testFetch(): void
         self::assertSame([], $fetchedSummary->values[3]->metricNameWithLabels->labels);
         self::assertSame(5, $fetchedSummary->values[3]->value);
     }
+
+    /**
+     * Storage can return metric that was removed from the registry, it shouldn't break the fetcher
+     */
+    public function testRemovedMetricExistsInStorage(): void
+    {
+        $counterStorage = new InMemoryCounterStorage();
+
+        $counter = new Counter('foo_counter', 'help');
+
+        $counterCollector = new CounterCollector(
+            $counter,
+            $counterStorage,
+            new NullLogger(),
+        );
+
+        $counterCollector->increment();
+
+        $fetcher = new StoredMetricsFetcher(
+            registry: new ArrayRegistry(),
+            counterStorage: $counterStorage,
+            gaugeStorage: new GaugeStorageStub(),
+            histogramStorage: new HistogramStorageStub(),
+            summaryStorage: new SummaryStorageStub(),
+        );
+
+        $fetched = [...$fetcher->fetch()];
+
+        self::assertEmpty($fetched);
+    }
 }