Catch invalid JSON from Redis and throw an error

src/Prometheus/Exception/MetricJsonException.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace Prometheus\Exception;
+
+use Exception;
+
+/**
+ * Exception thrown if a metric can't be found in the CollectorRegistry.
+ */
+class MetricJsonException extends Exception
+{
+
+    private $metricName;
+    public function __construct($message = "", $code = 0, Exception $previous = null, ?string $metricName = null)
+    {
+        parent::__construct($message, $code, $previous);
+        $this->metricName = $metricName;
+    }
+
+    public function getMetricName(): ?string
+    {
+        return $this->metricName;
+    }
+}

src/Prometheus/Storage/Redis.php

@@ -6,6 +6,7 @@
 
 use InvalidArgumentException;
 use Prometheus\Counter;
+use Prometheus\Exception\MetricJsonException;
 use Prometheus\Exception\StorageException;
 use Prometheus\Gauge;
 use Prometheus\Histogram;
@@ -432,6 +433,9 @@ private function collectHistograms(): array
                 }
                 $allLabelValues[] = $d['labelValues'];
             }
+            if (json_last_error() !== JSON_ERROR_NONE) {
+                $this->throwMetricJsonException($key);
+            }
 
             // We need set semantics.
             // This is the equivalent of array_unique but for arrays of arrays.
@@ -618,6 +622,9 @@ private function collectGauges(bool $sortMetrics = true): array
                     'labelValues' => json_decode($k, true),
                     'value' => $value,
                 ];
+                if (json_last_error() !== JSON_ERROR_NONE) {
+                    $this->throwMetricJsonException($key, $gauge['name']);
+                }
             }
 
             if ($sortMetrics) {
@@ -633,6 +640,7 @@ private function collectGauges(bool $sortMetrics = true): array
 
     /**
      * @return mixed[]
+     * @throws MetricJsonException
      */
     private function collectCounters(bool $sortMetrics = true): array
     {
@@ -645,6 +653,7 @@ private function collectCounters(bool $sortMetrics = true): array
                 continue;
             }
             $counter = json_decode($raw['__meta'], true);
+
             unset($raw['__meta']);
             $counter['samples'] = [];
             foreach ($raw as $k => $value) {
@@ -654,6 +663,10 @@ private function collectCounters(bool $sortMetrics = true): array
                     'labelValues' => json_decode($k, true),
                     'value' => $value,
                 ];
+
+                if (json_last_error() !== JSON_ERROR_NONE) {
+                    $this->throwMetricJsonException($key, $counter['name']);
+                }
             }
 
             if ($sortMetrics) {
@@ -725,4 +738,17 @@ private function decodeLabelValues(string $values): array
         }
         return $decodedValues;
     }
+
+    /**
+     * @param string $redisKey
+     * @param string|null $metricName
+     * @return void
+     * @throws MetricJsonException
+     */
+    private function throwMetricJsonException(string $redisKey, ?string $metricName = null): void
+    {
+        $metricName = $metricName ?? 'unknown';
+        $message = 'Json error: ' . json_last_error_msg() . ' redis key : ' . $redisKey . ' metric name: ' . $metricName;
+        throw new MetricJsonException($message, 0, null, $metricName);
+    }
 }

src/Prometheus/Storage/RedisNg.php

@@ -6,6 +6,7 @@
 
 use InvalidArgumentException;
 use Prometheus\Counter;
+use Prometheus\Exception\MetricJsonException;
 use Prometheus\Exception\StorageException;
 use Prometheus\Gauge;
 use Prometheus\Histogram;
@@ -405,6 +406,7 @@ private function metaData(array $data): array
 
     /**
      * @return mixed[]
+     * @throws MetricJsonException
      */
     private function collectHistograms(): array
     {
@@ -429,6 +431,10 @@ private function collectHistograms(): array
                 $allLabelValues[] = $d['labelValues'];
             }
 
+            if (json_last_error() !== JSON_ERROR_NONE) {
+                $this->throwMetricJsonException($key);
+            }
+
             // We need set semantics.
             // This is the equivalent of array_unique but for arrays of arrays.
             $allLabelValues = array_map("unserialize", array_unique(array_map("serialize", $allLabelValues)));
@@ -599,6 +605,9 @@ private function collectGauges(bool $sortMetrics = true): array
                     'labelValues' => json_decode($k, true),
                     'value' => $value,
                 ];
+                if (json_last_error() !== JSON_ERROR_NONE) {
+                    $this->throwMetricJsonException($key, $gauge['name']);
+                }
             }
 
             if ($sortMetrics) {
@@ -614,6 +623,7 @@ private function collectGauges(bool $sortMetrics = true): array
 
     /**
      * @return mixed[]
+     * @throws MetricJsonException
      */
     private function collectCounters(bool $sortMetrics = true): array
     {
@@ -632,6 +642,9 @@ private function collectCounters(bool $sortMetrics = true): array
                     'labelValues' => json_decode($k, true),
                     'value' => $value,
                 ];
+                if (json_last_error() !== JSON_ERROR_NONE) {
+                    $this->throwMetricJsonException($key, $counter['name']);
+                }
             }
 
             if ($sortMetrics) {
@@ -703,4 +716,17 @@ private function decodeLabelValues(string $values): array
         }
         return $decodedValues;
     }
+
+    /**
+     * @param string $redisKey
+     * @param string|null $metricName
+     * @return void
+     * @throws MetricJsonException
+     */
+    private function throwMetricJsonException(string $redisKey, ?string $metricName = null): void
+    {
+        $metricName = $metricName ?? 'unknown';
+        $message = 'Json error: ' . json_last_error_msg() . ' redis key : ' . $redisKey . ' metric name: ' . $metricName;
+        throw new MetricJsonException($message, 0, null, $metricName);
+    }
 }