From a258f1424ad907a40bcc1630be2cd4860c378b9d Mon Sep 17 00:00:00 2001
From: Nikita Salnikov-Tarnovski <gnikem@gmail.com>
Date: Wed, 20 May 2020 23:47:25 +0300
Subject: [PATCH] Fix khttp instrumentation in case of absent or read-only
 headers map (#416)

---
 .../instrumentation/khttp/KHttpAdvice.java     |  5 +++--
 .../khttp/KHttpHeadersInjectAdapter.java       | 18 ++----------------
 2 files changed, 5 insertions(+), 18 deletions(-)

diff --git a/instrumentation/khttp-0.1/src/main/java/io/opentelemetry/auto/instrumentation/khttp/KHttpAdvice.java b/instrumentation/khttp-0.1/src/main/java/io/opentelemetry/auto/instrumentation/khttp/KHttpAdvice.java
index d04bc8d65f..31a7999b79 100644
--- a/instrumentation/khttp-0.1/src/main/java/io/opentelemetry/auto/instrumentation/khttp/KHttpAdvice.java
+++ b/instrumentation/khttp-0.1/src/main/java/io/opentelemetry/auto/instrumentation/khttp/KHttpAdvice.java
@@ -39,7 +39,7 @@ public class KHttpAdvice {
   public static SpanWithScope methodEnter(
       @Advice.Argument(value = 0) String method,
       @Advice.Argument(value = 1) String uri,
-      @Advice.Argument(value = 2) Map<String, String> headers) {
+      @Advice.Argument(value = 2, readOnly = false) Map<String, String> headers) {
 
     final int callDepth = CallDepthThreadLocalMap.incrementCallDepth(KHttp.class);
     if (callDepth > 0) {
@@ -53,7 +53,8 @@ public class KHttpAdvice {
 
     final Context context = withSpan(span, Context.current());
 
-    OpenTelemetry.getPropagators().getHttpTextFormat().inject(context, asWritable(headers), SETTER);
+    headers = asWritable(headers);
+    OpenTelemetry.getPropagators().getHttpTextFormat().inject(context, headers, SETTER);
     return new SpanWithScope(span, withScopedContext(context));
   }
 
diff --git a/instrumentation/khttp-0.1/src/main/java/io/opentelemetry/auto/instrumentation/khttp/KHttpHeadersInjectAdapter.java b/instrumentation/khttp-0.1/src/main/java/io/opentelemetry/auto/instrumentation/khttp/KHttpHeadersInjectAdapter.java
index 1809f7127c..ce321eba37 100644
--- a/instrumentation/khttp-0.1/src/main/java/io/opentelemetry/auto/instrumentation/khttp/KHttpHeadersInjectAdapter.java
+++ b/instrumentation/khttp-0.1/src/main/java/io/opentelemetry/auto/instrumentation/khttp/KHttpHeadersInjectAdapter.java
@@ -21,23 +21,9 @@ import java.util.Map;
 
 public class KHttpHeadersInjectAdapter implements HttpTextFormat.Setter<Map<String, String>> {
 
-  private static Class emptyMap;
-
-  static {
-    try {
-      emptyMap = Class.forName("kotlin.collections.EmptyMap");
-    } catch (ClassNotFoundException e) {
-    }
-  }
-
   public static Map<String, String> asWritable(Map<String, String> headers) {
-    // EmptyMap is read-only so we have to substitute it with writable instance to be able to inject
-    // headers
-    if (emptyMap != null && emptyMap.isInstance(headers)) {
-      return new HashMap<>();
-    } else {
-      return headers;
-    }
+    // Kotlin likes to use read-only data structures, so wrap into new writable map
+    return new HashMap<>(headers);
   }
 
   public static final KHttpHeadersInjectAdapter SETTER = new KHttpHeadersInjectAdapter();