Merge pull request #15 from andrew-demb/denylist-operations-sampling

Provide way to disable sampling based on operation name

Author: allflame

README.md

@@ -12,3 +12,27 @@ return [
     // ...
 ];
 ```
+
+## Denylist sampling operations 
+
+This feature allows to disable sampling for deny-listed operations.
+
+It will be useful when your infrastructure initiates some operations which you are
+not insterested for tracking in Jaeger.
+
+Operation names used in package configuration refers to first (parent) span operation name
+(https://www.jaegertracing.io/docs/latest/architecture/#span).
+
+> Hint: if you use default name generator (class `\Jaeger\Symfony\Name\Generator\DefaultNameGenerator`),
+> your operation name for HTTP requests will be the same as matched symfony route name.
+
+Example bundle config with denylist feature:
+
+```yaml
+# config/jaeger.yaml
+jaeger:
+  denylist:
+    operation_names:
+      - 'healthcheck'
+      - 'metrics'
+```

src/DependencyInjection/Configuration.php

@@ -0,0 +1,36 @@
+<?php
+declare(strict_types=1);
+
+namespace Jaeger\Symfony\DependencyInjection;
+
+use Symfony\Component\Config\Definition\Builder\TreeBuilder;
+use Symfony\Component\Config\Definition\ConfigurationInterface;
+
+final class Configuration implements ConfigurationInterface
+{
+    public function getConfigTreeBuilder(): TreeBuilder
+    {
+        $treeBuilder = new TreeBuilder('jaeger');
+        if (true === method_exists($treeBuilder, 'getRootNode')) {
+            $rootNode = $treeBuilder->getRootNode();
+        } else {
+            $rootNode = $treeBuilder->root('jaeger', 'array');
+        }
+
+        // @formatter:off
+        $rootNode
+            ->children()
+                ->arrayNode('denylist')
+                    ->canBeEnabled()
+                    ->children()
+                        ->arrayNode('operation_names')
+                            ->scalarPrototype()->end()
+                        ->end()
+                    ->end()
+                ->end()
+            ->end();
+        // @formatter:on
+
+        return $treeBuilder;
+    }
+}

src/DependencyInjection/JaegerExtension.php

@@ -18,5 +18,13 @@ public function load(array $configs, ContainerBuilder $container)
             new FileLocator(__DIR__ . '/../Resources')
         );
         $loader->load('services.yml');
+
+        $configuration = new Configuration();
+        $config = $this->processConfiguration($configuration, $configs);
+
+        if ($this->isConfigEnabled($container, $config['denylist'])) {
+            $container->setParameter('jaeger.sampler.operation_denylist', $config['denylist']['operation_names']);
+            $loader->load('denylist.yml');
+        }
     }
 }

src/Resources/denylist.yml

@@ -0,0 +1,12 @@
+parameters:
+  # Will be configured in DI extension
+  # jaeger.sampler.operation_denylist: []
+
+services:
+  jaeger.sampler.denylist:
+    class: Jaeger\Symfony\Sampler\DenylistOperationsSampler
+    decorates: jaeger.sampler
+    decoration_priority: 10
+    arguments:
+      - '@jaeger.sampler.denylist.inner'
+      - '%jaeger.sampler.operation_denylist%'

src/Sampler/DenylistOperationsSampler.php

@@ -0,0 +1,50 @@
+<?php
+declare(strict_types=1);
+
+namespace Jaeger\Symfony\Sampler;
+
+use Jaeger\Sampler\SamplerDecisionTag;
+use Jaeger\Sampler\SamplerFlagsTag;
+use Jaeger\Sampler\SamplerInterface;
+use Jaeger\Sampler\SamplerParamTag;
+use Jaeger\Sampler\SamplerResult;
+use Jaeger\Sampler\SamplerTypeTag;
+
+final class DenylistOperationsSampler implements SamplerInterface
+{
+    private $sampler;
+
+    private $denylistedOperationsMap;
+
+    /**
+     * @var SamplerInterface $sampler
+     * @var string[]         $denylistedOperations
+     */
+    public function __construct(SamplerInterface $sampler, array $denylistedOperations)
+    {
+        $this->sampler = $sampler;
+        $this->denylistedOperationsMap = \array_fill_keys($denylistedOperations, true);
+    }
+
+    public function decide(int $traceId, string $operationName, string $debugId): SamplerResult
+    {
+        if ('' !== $debugId) {
+            return $this->sampler->decide($traceId, $operationName, $debugId);
+        }
+
+        if (false === \array_key_exists($operationName, $this->denylistedOperationsMap)) {
+            return $this->sampler->decide($traceId, $operationName, $debugId);
+        }
+
+        return new SamplerResult(
+            false,
+            0,
+            [
+                new SamplerTypeTag('denylist_operations'),
+                new SamplerParamTag($operationName),
+                new SamplerDecisionTag(false),
+                new SamplerFlagsTag(0x00),
+            ]
+        );
+    }
+}