From 10d93ac2a010edcb0add890efb3af631ad369b90 Mon Sep 17 00:00:00 2001
From: Trask Stalnaker <trask.stalnaker@gmail.com>
Date: Wed, 1 Apr 2020 10:49:45 -0700
Subject: [PATCH] Fix double log capture (#299)

---
 .../log4j/v2_0/Log4jSpansInstrumentation.java   | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/instrumentation/log4j/log4j-2.0/src/main/java/io/opentelemetry/auto/instrumentation/log4j/v2_0/Log4jSpansInstrumentation.java b/instrumentation/log4j/log4j-2.0/src/main/java/io/opentelemetry/auto/instrumentation/log4j/v2_0/Log4jSpansInstrumentation.java
index 5608a3b76570..4bb7291e8a22 100644
--- a/instrumentation/log4j/log4j-2.0/src/main/java/io/opentelemetry/auto/instrumentation/log4j/v2_0/Log4jSpansInstrumentation.java
+++ b/instrumentation/log4j/log4j-2.0/src/main/java/io/opentelemetry/auto/instrumentation/log4j/v2_0/Log4jSpansInstrumentation.java
@@ -85,12 +85,25 @@ public Map<? extends ElementMatcher<? super MethodDescription>, String> transfor
   public static class LogMessageAdvice {
 
     @Advice.OnMethodEnter(suppress = Throwable.class)
-    public static void methodEnter(
+    public static boolean methodEnter(
         @Advice.This final Logger logger,
         @Advice.Argument(1) final Level level,
         @Advice.Argument(3) final Message message,
         @Advice.Argument(4) final Throwable t) {
-      Log4jSpans.capture(logger, level, message, t);
+      // need to track call depth across all loggers in order to avoid double capture when one
+      // logging framework delegates to another
+      final boolean topLevel = CallDepthThreadLocalMap.incrementCallDepth("logger") == 0;
+      if (topLevel) {
+        Log4jSpans.capture(logger, level, message, t);
+      }
+      return topLevel;
+    }
+
+    @Advice.OnMethodExit(onThrowable = Throwable.class, suppress = Throwable.class)
+    public static void methodExit(@Advice.Enter final boolean topLevel) {
+      if (topLevel) {
+        CallDepthThreadLocalMap.reset("logger");
+      }
     }
   }