From 6966bf80497f5b4644db474babf661b226d11de5 Mon Sep 17 00:00:00 2001
From: Markus Spann <Markus.Spann@baaderbank.de>
Date: Fri, 9 Jul 2021 16:08:18 +0200
Subject: [PATCH 1/3] LOG4J2-3121: log4j2 config modified at run-time may
 trigger incomplete MBean re-initialization due to
 InstanceAlreadyExistsException

---
 .../java/org/apache/logging/log4j/core/jmx/Server.java    | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/log4j-core/src/main/java/org/apache/logging/log4j/core/jmx/Server.java b/log4j-core/src/main/java/org/apache/logging/log4j/core/jmx/Server.java
index 04eaa3d411b..441573e915d 100644
--- a/log4j-core/src/main/java/org/apache/logging/log4j/core/jmx/Server.java
+++ b/log4j-core/src/main/java/org/apache/logging/log4j/core/jmx/Server.java
@@ -389,7 +389,15 @@ private static void registerAppenders(final LoggerContext ctx, final MBeanServer
 
     private static void register(final MBeanServer mbs, final Object mbean, final ObjectName objectName)
             throws InstanceAlreadyExistsException, MBeanRegistrationException, NotCompliantMBeanException {
+        if (mbs.isRegistered(objectName)) {
+            try {
+                mbs.unregisterMBean(objectName);
+            } catch (MBeanRegistrationException | InstanceNotFoundException _ex) {
+                LOGGER.trace("Failed to unregister MBean {}", objectName);
+            }
+        }
         LOGGER.debug("Registering MBean {}", objectName);
         mbs.registerMBean(mbean, objectName);
     }
+
 }

From d263b183f65a53f762aaae724cf67c73b4d4b3c1 Mon Sep 17 00:00:00 2001
From: Markus Spann <Markus.Spann@baaderbank.de>
Date: Fri, 9 Jul 2021 16:57:46 +0200
Subject: [PATCH 2/3] LOG4J2-3121: Update for codestyle

---
 .../src/main/java/org/apache/logging/log4j/core/jmx/Server.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/log4j-core/src/main/java/org/apache/logging/log4j/core/jmx/Server.java b/log4j-core/src/main/java/org/apache/logging/log4j/core/jmx/Server.java
index 441573e915d..baf1f96f5fa 100644
--- a/log4j-core/src/main/java/org/apache/logging/log4j/core/jmx/Server.java
+++ b/log4j-core/src/main/java/org/apache/logging/log4j/core/jmx/Server.java
@@ -392,7 +392,7 @@ private static void register(final MBeanServer mbs, final Object mbean, final Ob
         if (mbs.isRegistered(objectName)) {
             try {
                 mbs.unregisterMBean(objectName);
-            } catch (MBeanRegistrationException | InstanceNotFoundException _ex) {
+            } catch (MBeanRegistrationException | InstanceNotFoundException ex) {
                 LOGGER.trace("Failed to unregister MBean {}", objectName);
             }
         }

From 131cfa7d86e269ec3e7fd301dc3768dc385e1ad8 Mon Sep 17 00:00:00 2001
From: Markus Spann <Markus.Spann@baaderbank.de>
Date: Fri, 9 Jul 2021 17:22:20 +0200
Subject: [PATCH 3/3] LOG4J2-3121: Updated changes.xml with bugfix info

---
 src/changes/changes.xml | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/changes/changes.xml b/src/changes/changes.xml
index 3a787518b13..e29389c1123 100644
--- a/src/changes/changes.xml
+++ b/src/changes/changes.xml
@@ -69,6 +69,9 @@
         Allow a PatternSelector to be specified on GelfLayout.
       </action>
       <!-- FIXES -->
+      <action issue="LOG4J2-3121" dev="ggregory" type="fix" due-to="Markus Spann">
+          log4j2 config modified at run-time may trigger incomplete MBean re-initialization due to InstanceAlreadyExistsException.
+      </action>
       <action issue="LOG4J2-3080" dev="vy" type="fix">
         Use SimpleMessage in Log4j 1 Category whenever possible.
       </action>