From cecfc3461bcbceb79b6a58b33d4d320a28fc7acf Mon Sep 17 00:00:00 2001
From: John Watson <jkwatson@gmail.com>
Date: Thu, 1 Jul 2021 06:16:17 -0700
Subject: [PATCH] Best effort at recording the content length on a http
 response. (#60)

---
 .../com/splunk/rum/OkHttpRumInterceptor.java  | 19 ++++++++++++++++++-
 .../splunk/rum/OkHttpRumInterceptorTest.java  |  2 ++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/splunk-otel-android/src/main/java/com/splunk/rum/OkHttpRumInterceptor.java b/splunk-otel-android/src/main/java/com/splunk/rum/OkHttpRumInterceptor.java
index e241a934..ffc7ba8b 100644
--- a/splunk-otel-android/src/main/java/com/splunk/rum/OkHttpRumInterceptor.java
+++ b/splunk-otel-android/src/main/java/com/splunk/rum/OkHttpRumInterceptor.java
@@ -23,6 +23,7 @@
 
 import io.opentelemetry.api.common.AttributeKey;
 import io.opentelemetry.api.trace.Span;
+import io.opentelemetry.semconv.trace.attributes.SemanticAttributes;
 import okhttp3.Call;
 import okhttp3.Connection;
 import okhttp3.Interceptor;
@@ -78,13 +79,14 @@ public Response proceed(@NotNull Request request) throws IOException {
             Span span = Span.current();
             span.setAttribute(SplunkRum.COMPONENT_KEY, "http");
 
-            Response response = null;
+            Response response;
             try {
                 response = chain.proceed(request);
             } catch (IOException e) {
                 SplunkRum.addExceptionAttributes(span, e);
                 throw e;
             }
+            recordContentLength(span, response);
 
             String serverTimingHeader = response.header("Server-Timing");
 
@@ -96,6 +98,21 @@ public Response proceed(@NotNull Request request) throws IOException {
             return response;
         }
 
+        private void recordContentLength(Span span, Response response) {
+            //make a best low-impact effort at getting the content length on the response.
+            String contentLengthHeader = response.header("Content-Length");
+            if (contentLengthHeader != null) {
+                try {
+                    long contentLength = Long.parseLong(contentLengthHeader);
+                    if (contentLength > 0) {
+                        span.setAttribute(SemanticAttributes.HTTP_RESPONSE_CONTENT_LENGTH, contentLength);
+                    }
+                } catch (NumberFormatException e) {
+                    //who knows what we got back? It wasn't a number!
+                }
+            }
+        }
+
         @Override
         public Connection connection() {
             return chain.connection();
diff --git a/splunk-otel-android/src/test/java/com/splunk/rum/OkHttpRumInterceptorTest.java b/splunk-otel-android/src/test/java/com/splunk/rum/OkHttpRumInterceptorTest.java
index 32773b01..255bec42 100644
--- a/splunk-otel-android/src/test/java/com/splunk/rum/OkHttpRumInterceptorTest.java
+++ b/splunk-otel-android/src/test/java/com/splunk/rum/OkHttpRumInterceptorTest.java
@@ -67,6 +67,7 @@ public void spanDecoration() throws IOException {
                 .message("hello")
                 .code(200)
                 .addHeader("Server-Timing", "headerValue")
+                .addHeader("Content-Length", "101")
                 .build());
 
         OkHttpRumInterceptor interceptor = new OkHttpRumInterceptor(new TestTracingInterceptor(tracer), headerParser);
@@ -78,6 +79,7 @@ public void spanDecoration() throws IOException {
         assertEquals("http", spanData.getAttributes().get(SplunkRum.COMPONENT_KEY));
         assertEquals("9499195c502eb217c448a68bfe0f967c", spanData.getAttributes().get(OkHttpRumInterceptor.LINK_TRACE_ID_KEY));
         assertEquals("fe16eca542cd5d86", spanData.getAttributes().get(OkHttpRumInterceptor.LINK_SPAN_ID_KEY));
+        assertEquals(101L, (long) spanData.getAttributes().get(SemanticAttributes.HTTP_RESPONSE_CONTENT_LENGTH));
     }
 
     @Test