Fix fatal error in redis when meta information is missing in metrics collection (#111)

Signed-off-by: m-idler <marcel.idler@mayflower.de>

Author: m-idler

src/Prometheus/Storage/Redis.php

@@ -396,6 +396,9 @@ private function collectHistograms(): array
         $histograms = [];
         foreach ($keys as $key) {
             $raw = $this->redis->hGetAll(str_replace($this->redis->_prefix(''), '', $key));
+            if (!isset($raw['__meta'])) {
+                continue;
+            }
             $histogram = json_decode($raw['__meta'], true);
             unset($raw['__meta']);
             $histogram['samples'] = [];
@@ -576,6 +579,9 @@ private function collectGauges(): array
         $gauges = [];
         foreach ($keys as $key) {
             $raw = $this->redis->hGetAll(str_replace($this->redis->_prefix(''), '', $key));
+            if (!isset($raw['__meta'])) {
+                continue;
+            }
             $gauge = json_decode($raw['__meta'], true);
             unset($raw['__meta']);
             $gauge['samples'] = [];
@@ -605,6 +611,9 @@ private function collectCounters(): array
         $counters = [];
         foreach ($keys as $key) {
             $raw = $this->redis->hGetAll(str_replace($this->redis->_prefix(''), '', $key));
+            if (!isset($raw['__meta'])) {
+                continue;
+            }
             $counter = json_decode($raw['__meta'], true);
             unset($raw['__meta']);
             $counter['samples'] = [];

tests/Test/Prometheus/Storage/RedisTest.php

@@ -146,4 +146,33 @@ public function itShouldOnlyConnectOnceForInjectedRedisConnectionOnSubsequentCal
             $this->redisConnection->rawCommand('client', 'list')
         );
     }
+
+    /**
+     * @test
+     */
+    public function itShouldCollectMetricsAndIgnoreInvalidMetricsWithoutMetaData(): void
+    {
+        $redisConnection = $this->createMock(\Redis::class);
+        $redisConnection->method('isConnected')->willReturn(true);
+        $redisConnection->method('_prefix')->willReturnArgument(0);
+        $redisConnection->method('keys')->with('PROMETHEUS_summary_METRIC_KEYS:*:meta')->willReturn([]);
+        $redisConnection->method('sMembers')
+            ->withConsecutive(
+                ['PROMETHEUS_histogram_METRIC_KEYS'],
+                ['PROMETHEUS_gauge_METRIC_KEYS'],
+                ['PROMETHEUS_counter_METRIC_KEYS']
+            )
+            ->willReturnOnConsecutiveCalls(
+                ['key_histogramm'],
+                ['key_gauge'],
+                ['key_counter'],
+            )
+        ;
+        $redisConnection->method('hGetAll')->willReturn(['any_invalid_data' => '']);
+
+        $redis = Redis::fromExistingConnection($redisConnection);
+        $metrics = $redis->collect();
+
+        self::assertEquals([], $metrics);
+    }
 }