[RenderTextFormat] Allow value errors to be rendered as comments.

joec4i · joec4i · commit dc0e6ce2b85f · 2023-12-20T17:15:52.000+11:00
Redis and RedisNg allow samples with mismatching labels to be stored, which could cause ValueError to be thrown when
rendering. Rendering would fail as a result, which is not ideal.

- Change render() to accept an optional $silent parameter. When set to true, render the errors as comments instead of
  throwing them and failing the whole operation.

Signed-off-by: Joe Cai &lt;joe.cai@bigcommerce.com&gt;
diff --git a/src/Prometheus/RenderTextFormat.php b/src/Prometheus/RenderTextFormat.php
@@ -5,16 +5,18 @@
 namespace Prometheus;
 
 use RuntimeException;
+use Throwable;
 
 class RenderTextFormat implements RendererInterface
 {
     const MIME_TYPE = 'text/plain; version=0.0.4';
 
     /**
      * @param MetricFamilySamples[] $metrics
+     * @param bool $silent If true, render value errors as comments instead of throwing them.
      * @return string
      */
-    public function render(array $metrics): string
+    public function render(array $metrics, bool $silent = false): string
     {
         usort($metrics, function (MetricFamilySamples $a, MetricFamilySamples $b): int {
             return strcmp($a->getName(), $b->getName());
@@ -25,7 +27,20 @@ public function render(array $metrics): string
             $lines[] = "# HELP " . $metric->getName() . " {$metric->getHelp()}";
             $lines[] = "# TYPE " . $metric->getName() . " {$metric->getType()}";
             foreach ($metric->getSamples() as $sample) {
-                $lines[] = $this->renderSample($metric, $sample);
+                try {
+                    $lines[] = $this->renderSample($metric, $sample);
+                } catch (Throwable $e) {
+                    // Redis and RedisNg allow samples with mismatching labels to be stored, which could cause ValueError
+                    // to be thrown when rendering. If this happens, users can decide whether to ignore the error or not.
+                    // These errors will normally disappear after the storage is flushed.
+                    if (!$silent) {
+                        throw $e;
+                    }
+
+                    $lines[] = "# Error: {$e->getMessage()}";
+                    $lines[] = "#   Labels: " . json_encode(array_merge($metric->getLabelNames(), $sample->getLabelNames()));
+                    $lines[] = "#   Values: " . json_encode(array_merge($sample->getLabelValues()));
+                }
             }
         }
         return implode("\n", $lines) . "\n";
diff --git a/tests/Test/Prometheus/RenderTextFormatTest.php b/tests/Test/Prometheus/RenderTextFormatTest.php
@@ -10,6 +10,8 @@
 use Prometheus\RenderTextFormat;
 use PHPUnit\Framework\TestCase;
 use Prometheus\Storage\InMemory;
+use Prometheus\Storage\Redis;
+use ValueError;
 
 class RenderTextFormatTest extends TestCase
 {
@@ -70,4 +72,58 @@ private function getExpectedOutput(): string
 
 TEXTPLAIN;
     }
+
+    public function testValueErrorThrownWithInvalidSamples(): void
+    {
+        $namespace = 'foo';
+        $counter = 'bar';
+        $storage = new Redis(['host' => REDIS_HOST]);
+        $storage->wipeStorage();
+
+        $registry = new CollectorRegistry($storage, false);
+        $registry->registerCounter($namespace, $counter, 'counter-help-text', ['label1', 'label2'])
+            ->inc(['bob', 'alice']);
+
+        // Reload the registry with an updated counter config
+        $registry = new CollectorRegistry($storage, false);
+        $registry->registerCounter($namespace, $counter, 'counter-help-text', ['label1', 'label2', 'label3'])
+            ->inc(['bob', 'alice', 'eve']);
+
+        $this->expectException(ValueError::class);
+
+        $renderer = new RenderTextFormat();
+        $renderer->render($registry->getMetricFamilySamples());
+
+    }
+
+    public function testOutputWithInvalidSamplesSkipped(): void
+    {
+        $namespace = 'foo';
+        $counter = 'bar';
+        $storage = new Redis(['host' => REDIS_HOST]);
+        $storage->wipeStorage();
+
+        $registry = new CollectorRegistry($storage, false);
+        $registry->registerCounter($namespace, $counter, 'counter-help-text', ['label1', 'label2'])
+            ->inc(['bob', 'alice']);
+
+        // Reload the registry with an updated counter config
+        $registry = new CollectorRegistry($storage, false);
+        $registry->registerCounter($namespace, $counter, 'counter-help-text', ['label1', 'label2', 'label3'])
+            ->inc(['bob', 'alice', 'eve']);
+
+        $expectedOutput = '
+# HELP foo_bar counter-help-text
+# TYPE foo_bar counter
+foo_bar{label1="bob",label2="alice"} 1
+# Error: array_combine(): Argument #1 ($keys) and argument #2 ($values) must have the same number of elements
+#   Labels: ["label1","label2"]
+#   Values: ["bob","alice","eve"]
+';
+
+        $renderer = new RenderTextFormat();
+        $output = $renderer->render($registry->getMetricFamilySamples(), true);
+
+        self::assertSame(trim($expectedOutput), trim($output));
+    }
 }
