Make APCu key prefix configurable (#46)

Author: gkralik

src/Prometheus/Storage/APC.php

@@ -11,21 +11,29 @@
 
 class APC implements Adapter
 {
+    /** @var string Default prefix to use for APC keys. */
     const PROMETHEUS_PREFIX = 'prom';
 
+    /** @var string Prefix to use for APC keys. */
+    private $prometheusPrefix;
+
     /**
      * APC constructor.
      *
+     * @param string $prometheusPrefix Prefix for APCu keys (defaults to {@see PROMETHEUS_PREFIX}).
+     *
      * @throws StorageException
      */
-    public function __construct()
+    public function __construct(string $prometheusPrefix = self::PROMETHEUS_PREFIX)
     {
         if (!extension_loaded('apcu')) {
             throw new StorageException('APCu extension is not loaded');
         }
         if (!apcu_enabled()) {
             throw new StorageException('APCu is not enabled');
         }
+
+        $this->prometheusPrefix = $prometheusPrefix;
     }
 
     /**
@@ -145,7 +153,7 @@ public function wipeStorage(): void
         //                    ^       | match from first character only
         //                     %s:    | common prefix substitute with colon suffix
         //                        .+  | at least one additional character
-        $matchAll = sprintf('/^%s:.+/', self::PROMETHEUS_PREFIX);
+        $matchAll = sprintf('/^%s:.+/', $this->prometheusPrefix);
 
         foreach (new APCUIterator($matchAll) as $key => $value) {
             apcu_delete($key);
@@ -158,7 +166,7 @@ public function wipeStorage(): void
      */
     private function metaKey(array $data): string
     {
-        return implode(':', [self::PROMETHEUS_PREFIX, $data['type'], $data['name'], 'meta']);
+        return implode(':', [$this->prometheusPrefix, $data['type'], $data['name'], 'meta']);
     }
 
     /**
@@ -168,7 +176,7 @@ private function metaKey(array $data): string
     private function valueKey(array $data): string
     {
         return implode(':', [
-            self::PROMETHEUS_PREFIX,
+            $this->prometheusPrefix,
             $data['type'],
             $data['name'],
             $this->encodeLabelValues($data['labelValues']),
@@ -184,7 +192,7 @@ private function valueKey(array $data): string
     private function histogramBucketValueKey(array $data, $bucket): string
     {
         return implode(':', [
-            self::PROMETHEUS_PREFIX,
+            $this->prometheusPrefix,
             $data['type'],
             $data['name'],
             $this->encodeLabelValues($data['labelValues']),
@@ -210,7 +218,7 @@ private function metaData(array $data): array
     private function collectCounters(): array
     {
         $counters = [];
-        foreach (new APCUIterator('/^prom:counter:.*:meta/') as $counter) {
+        foreach (new APCUIterator('/^' . $this->prometheusPrefix . ':counter:.*:meta/') as $counter) {
             $metaData = json_decode($counter['value'], true);
             $data = [
                 'name' => $metaData['name'],
@@ -219,7 +227,7 @@ private function collectCounters(): array
                 'labelNames' => $metaData['labelNames'],
                 'samples' => [],
             ];
-            foreach (new APCUIterator('/^prom:counter:' . $metaData['name'] . ':.*:value/') as $value) {
+            foreach (new APCUIterator('/^' . $this->prometheusPrefix . ':counter:' . $metaData['name'] . ':.*:value/') as $value) {
                 $parts = explode(':', $value['key']);
                 $labelValues = $parts[3];
                 $data['samples'][] = [
@@ -241,7 +249,7 @@ private function collectCounters(): array
     private function collectGauges(): array
     {
         $gauges = [];
-        foreach (new APCUIterator('/^prom:gauge:.*:meta/') as $gauge) {
+        foreach (new APCUIterator('/^' . $this->prometheusPrefix . ':gauge:.*:meta/') as $gauge) {
             $metaData = json_decode($gauge['value'], true);
             $data = [
                 'name' => $metaData['name'],
@@ -250,7 +258,7 @@ private function collectGauges(): array
                 'labelNames' => $metaData['labelNames'],
                 'samples' => [],
             ];
-            foreach (new APCUIterator('/^prom:gauge:' . $metaData['name'] . ':.*:value/') as $value) {
+            foreach (new APCUIterator('/^' . $this->prometheusPrefix . ':gauge:' . $metaData['name'] . ':.*:value/') as $value) {
                 $parts = explode(':', $value['key']);
                 $labelValues = $parts[3];
                 $data['samples'][] = [
@@ -273,7 +281,7 @@ private function collectGauges(): array
     private function collectHistograms(): array
     {
         $histograms = [];
-        foreach (new APCUIterator('/^prom:histogram:.*:meta/') as $histogram) {
+        foreach (new APCUIterator('/^' . $this->prometheusPrefix . ':histogram:.*:meta/') as $histogram) {
             $metaData = json_decode($histogram['value'], true);
             $data = [
                 'name' => $metaData['name'],
@@ -287,7 +295,7 @@ private function collectHistograms(): array
             $data['buckets'][] = '+Inf';
 
             $histogramBuckets = [];
-            foreach (new APCUIterator('/^prom:histogram:' . $metaData['name'] . ':.*:value/') as $value) {
+            foreach (new APCUIterator('/^' . $this->prometheusPrefix . ':histogram:' . $metaData['name'] . ':.*:value/') as $value) {
                 $parts = explode(':', $value['key']);
                 $labelValues = $parts[3];
                 $bucket = $parts[4];

tests/Test/Prometheus/Storage/APCTest.php

@@ -41,4 +41,29 @@ public function itShouldNotClearWholeAPCacheOnFlush(): void
             ])
         );
     }
+
+    /**
+     * @test
+     */
+    public function itShouldUseConfiguredPrefix(): void
+    {
+        $apc = new APC('custom_prefix');
+        $apc->wipeStorage();
+
+        $registry = new CollectorRegistry($apc);
+
+        $registry->getOrRegisterCounter('namespace', 'counter', 'counter help')->inc();
+        $registry->getOrRegisterGauge('namespace', 'gauge', 'gauge help')->inc();
+        $registry->getOrRegisterHistogram('namespace', 'histogram', 'histogram help')->observe(1);
+
+        $entries = iterator_to_array(new APCUIterator('/^custom_prefix:.*:meta$/'), true);
+
+        $cacheKeys = array_map(function ($item) {
+            return $item['key'];
+        }, $entries);
+
+        self::assertArrayHasKey('custom_prefix:counter:namespace_counter:meta', $cacheKeys);
+        self::assertArrayHasKey('custom_prefix:gauge:namespace_gauge:meta', $cacheKeys);
+        self::assertArrayHasKey('custom_prefix:histogram:namespace_histogram:meta', $cacheKeys);
+    }
 }