Prevent thread and object leak (#149)

* Prevent thread and object leak * Formatting * Avoid exception on shutdown * Improve exception handling on shutdown * Fix compile error
bluedenim · Apr 26, 2024 · 4029fed · 4029fed
1 parent 8f6d33b
commit 4029fed
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Showing 2 changed files with 23 additions and 3 deletions.
diff --git a/appender-core/src/main/java/com/van/logging/LoggingEventCache.java b/appender-core/src/main/java/com/van/logging/LoggingEventCache.java
@@ -285,6 +285,11 @@ public boolean stop() {
             cacheMonitor.shutDown();
         }
 
+        if (null != instances) {
+            // Remove the stopped cache from the queue to avoid a leak
+            instances.remove(this);
+        }
+
         return success;
     }
 }

diff --git a/appender-log4j2/src/main/java/com/van/logging/log4j2/Log4j2Appender.java b/appender-log4j2/src/main/java/com/van/logging/log4j2/Log4j2Appender.java
@@ -21,6 +21,7 @@
 public class Log4j2Appender extends AbstractAppender {
 
     private final LoggingEventCache eventCache;
+    private final Thread shutdownHook;
     private boolean verbose = false;
 
     @PluginBuilderFactory
@@ -38,7 +39,7 @@ public static org.apache.logging.log4j.core.util.Builder<Log4j2Appender> newBuil
         super(name, filter, layout, ignoreExceptions);
         Objects.requireNonNull(eventCache);
         this.eventCache = eventCache;
-        Runtime.getRuntime().addShutdownHook(new Thread(() -> {
+        this.shutdownHook = new Thread(() -> {
             try {
                 close();
                 LoggingEventCache.shutDown();
@@ -47,7 +48,8 @@ public static org.apache.logging.log4j.core.util.Builder<Log4j2Appender> newBuil
                     VansLogger.logger.error("InterruptedException during LoggingEventCache.shutDown", e);
                 }
             }
-        }));
+        });
+        Runtime.getRuntime().addShutdownHook(this.shutdownHook);
     }
 
     public Log4j2Appender setVerbose(boolean verbose) {
@@ -76,7 +78,7 @@ public void stop() {
     }
 
     Event mapToEvent(LogEvent event) {
-        String message = null;
+        String message;
         if (null != getLayout()) {
             message = getLayout().toSerializable(event).toString();
         } else {
@@ -97,6 +99,19 @@ private void close() {
         if (this.verbose) {
             VansLogger.logger.info("Publishing staging log on close...");
         }
+
+        // Deregister shutdown hook to avoid unbounded growth of registered hooks
+        try {
+            Runtime.getRuntime().removeShutdownHook(this.shutdownHook);
+        } catch (IllegalStateException e) {
+            // Swallow the exception
+            VansLogger.logger.warn("Already shutting down. Cannot remove shutdown hook.");
+        } catch (final Exception e) {
+            // Swallow the exception cause
+            VansLogger.logger.error("Error while removing shutdown hook", e);
+        }
+
+        // Flush and stop the cache associated with this appender
         eventCache.flushAndPublish(true);
         eventCache.stop();
     }