Enhance OpenTelemetry's DropTargetsSampler

This allows us to move effectively drop traces
belonging to SwaggerUI and other framework endpoints

Fixes: quarkusio#34376

extensions/opentelemetry/runtime/src/main/java/io/quarkus/opentelemetry/runtime/tracing/DropTargetsSampler.java

@@ -25,15 +25,44 @@ public SamplingResult shouldSample(Context parentContext, String traceId, String
 
         if (spanKind.equals(SpanKind.SERVER)) {
             String target = attributes.get(SemanticAttributes.HTTP_TARGET);
-            // TODO - radcortez - Match /* endpoints
-            if (target != null && dropTargets.contains(target)) {
+            if (shouldDrop(target)) {
                 return SamplingResult.drop();
             }
         }
 
         return sampler.shouldSample(parentContext, traceId, name, spanKind, attributes, parentLinks);
     }
 
+    /**
+     * Determines whether a path should be dropped
+     * TODO: this can certainly be optimized if we find that it's a hot-path
+     */
+    private boolean shouldDrop(String target) {
+        if ((target == null) || target.isEmpty()) {
+            return false;
+        }
+        if (safeContains(target)) { // check exact match
+            return true;
+        }
+        if (target.charAt(target.length() - 1) == '/') { // check if the path without the ending slash matched
+            if (safeContains(target.substring(0, target.length() - 1))) {
+                return true;
+            }
+        }
+        int lastSlashIndex = target.lastIndexOf('/');
+        if (lastSlashIndex != -1) {
+            if (safeContains(target.substring(0, lastSlashIndex) + "*")
+                    || safeContains(target.substring(0, lastSlashIndex) + "/*")) { // check if a wildcard matches
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private boolean safeContains(String target) {
+        return dropTargets.contains(target);
+    }
+
     @Override
     public String getDescription() {
         return sampler.getDescription();

extensions/opentelemetry/runtime/src/test/java/io/quarkus/opentelemetry/runtime/tracing/DropTargetsSamplerTest.java

@@ -0,0 +1,62 @@
+package io.quarkus.opentelemetry.runtime.tracing;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.List;
+import java.util.concurrent.atomic.AtomicLong;
+
+import org.junit.jupiter.api.Test;
+
+import io.opentelemetry.api.common.Attributes;
+import io.opentelemetry.api.trace.SpanKind;
+import io.opentelemetry.context.Context;
+import io.opentelemetry.sdk.trace.data.LinkData;
+import io.opentelemetry.sdk.trace.samplers.Sampler;
+import io.opentelemetry.sdk.trace.samplers.SamplingResult;
+import io.opentelemetry.semconv.trace.attributes.SemanticAttributes;
+
+class DropTargetsSamplerTest {
+
+    @Test
+    void testDropTargets() {
+        CountingSampler countingSampler = new CountingSampler();
+        var sut = new DropTargetsSampler(countingSampler, List.of("/q/swagger-ui", "/q/swagger-ui*"));
+
+        assertEquals(SamplingResult.recordAndSample(), getShouldSample(sut, "/other"));
+        assertEquals(1, countingSampler.count.get());
+
+        assertEquals(SamplingResult.drop(), getShouldSample(sut, "/q/swagger-ui"));
+        assertEquals(1, countingSampler.count.get());
+
+        assertEquals(SamplingResult.drop(), getShouldSample(sut, "/q/swagger-ui/"));
+        assertEquals(1, countingSampler.count.get());
+
+        assertEquals(SamplingResult.drop(), getShouldSample(sut, "/q/swagger-ui/whatever"));
+        assertEquals(1, countingSampler.count.get());
+
+        assertEquals(SamplingResult.recordAndSample(), getShouldSample(sut, "/q/test"));
+        assertEquals(2, countingSampler.count.get());
+    }
+
+    private static SamplingResult getShouldSample(DropTargetsSampler sut, String target) {
+        return sut.shouldSample(null, null, null, SpanKind.SERVER,
+                Attributes.of(SemanticAttributes.HTTP_TARGET, target), null);
+    }
+
+    private static final class CountingSampler implements Sampler {
+
+        final AtomicLong count = new AtomicLong(0);
+
+        @Override
+        public SamplingResult shouldSample(Context parentContext, String traceId, String name, SpanKind spanKind,
+                Attributes attributes, List<LinkData> parentLinks) {
+            count.incrementAndGet();
+            return SamplingResult.recordAndSample();
+        }
+
+        @Override
+        public String getDescription() {
+            return "test";
+        }
+    }
+}