X-Ray Sampler: Match rule's HTTP path against http.url attribute if target not present. (#141)

Author: anuraaga

aws-xray/src/main/java/io/opentelemetry/contrib/awsxray/SamplingRuleApplier.java

@@ -147,12 +147,15 @@ private SamplingRuleApplier(
   boolean matches(Attributes attributes, Resource resource) {
     int matchedAttributes = 0;
     String httpTarget = null;
+    String httpUrl = null;
     String httpMethod = null;
     String host = null;
 
     for (Map.Entry<AttributeKey<?>, Object> entry : attributes.asMap().entrySet()) {
       if (entry.getKey().equals(SemanticAttributes.HTTP_TARGET)) {
         httpTarget = (String) entry.getValue();
+      } else if (entry.getKey().equals(SemanticAttributes.HTTP_URL)) {
+        httpUrl = (String) entry.getValue();
       } else if (entry.getKey().equals(SemanticAttributes.HTTP_METHOD)) {
         httpMethod = (String) entry.getValue();
       } else if (entry.getKey().equals(SemanticAttributes.HTTP_HOST)) {
@@ -174,6 +177,22 @@ boolean matches(Attributes attributes, Resource resource) {
       return false;
     }
 
+    // URL Path may be in either http.target or http.url
+    if (httpTarget == null && httpUrl != null) {
+      int schemeEndIndex = httpUrl.indexOf("://");
+      // Per spec, http.url is always populated with scheme://host/target. If scheme doesn't
+      // match, assume it's bad instrumentation and ignore.
+      if (schemeEndIndex > 0) {
+        int pathIndex = httpUrl.indexOf('/', schemeEndIndex + "://".length());
+        if (pathIndex < 0) {
+          // No path, equivalent to root path.
+          httpTarget = "/";
+        } else {
+          httpTarget = httpUrl.substring(pathIndex);
+        }
+      }
+    }
+
     return urlPathMatcher.matches(httpTarget)
         && serviceNameMatcher.matches(resource.getAttribute(ResourceAttributes.SERVICE_NAME))
         && httpMethodMatcher.matches(httpMethod)

aws-xray/src/test/java/io/opentelemetry/contrib/awsxray/SamplingRuleApplierTest.java

@@ -104,6 +104,16 @@ void fixedRateAlwaysSample() {
     @Test
     void matches() {
       assertThat(applier.matches(attributes, resource)).isTrue();
+
+      // http.url works too
+      assertThat(
+              applier.matches(
+                  attributes.toBuilder()
+                      .remove(SemanticAttributes.HTTP_TARGET)
+                      .put(SemanticAttributes.HTTP_URL, "scheme://host:port/instrument-me")
+                      .build(),
+                  resource))
+          .isTrue();
     }
 
     @Test
@@ -143,6 +153,27 @@ void pathNotMatch() {
               .put(SemanticAttributes.HTTP_TARGET, "/instrument-you")
               .build();
       assertThat(applier.matches(attributes, resource)).isFalse();
+      attributes =
+          this.attributes.toBuilder()
+              .remove(SemanticAttributes.HTTP_TARGET)
+              .put(SemanticAttributes.HTTP_URL, "scheme://host:port/instrument-you")
+              .build();
+      assertThat(applier.matches(attributes, resource)).isFalse();
+      attributes =
+          this.attributes.toBuilder()
+              .remove(SemanticAttributes.HTTP_TARGET)
+              .put(SemanticAttributes.HTTP_URL, "scheme://host:port")
+              .build();
+      assertThat(applier.matches(attributes, resource)).isFalse();
+
+      // Correct path, but we ignore anyways since the URL is malformed per spec, scheme is always
+      // present.
+      attributes =
+          this.attributes.toBuilder()
+              .remove(SemanticAttributes.HTTP_TARGET)
+              .put(SemanticAttributes.HTTP_URL, "host:port/instrument-me")
+              .build();
+      assertThat(applier.matches(attributes, resource)).isFalse();
     }
 
     @Test