Expose disruptor discard count in LoggerContext

Author: adamthom-amzn

log4j-core/src/main/java/org/apache/logging/log4j/core/LoggerContext.java

@@ -802,4 +802,15 @@ private void initApiModule() {
     protected Logger newInstance(final LoggerContext ctx, final String name, final MessageFactory messageFactory) {
         return new Logger(ctx, name, messageFactory);
     }
+
+    /**
+     * Returns the number of logging events discarded by the disruptor's queue full policy, or 0 if the disruptor
+     * does not use a discarding policy or has not discarded. This is pulled from the disruptor used by this context's
+     * associated {@link org.apache.logging.log4j.core.async.AsyncLoggerConfigDelegate}
+     *
+     * @return 0 if the disruptor is not configured to discard or has not discarded, otherwise a positive long
+     */
+    public long getDiscardCount() {
+        return configuration.getAsyncLoggerConfigDelegate().getDiscardCount();
+    }
 }

log4j-core/src/main/java/org/apache/logging/log4j/core/async/AsyncLoggerConfigDelegate.java

@@ -62,4 +62,14 @@ public interface AsyncLoggerConfigDelegate {
      * @param logEventFactory the factory used
      */
     void setLogEventFactory(LogEventFactory logEventFactory);
+
+    /**
+     * Returns the number of logging events discarded by the disruptor's queue full policy, or 0 if the disruptor
+     * does not use a discarding policy or has not discarded.
+     *
+     * @return 0 if the disruptor is not configured to discard or has not discarded, otherwise a positive long
+     */
+    default long getDiscardCount() {
+        return 0;
+    }
 }

log4j-core/src/main/java/org/apache/logging/log4j/core/async/AsyncLoggerContext.java

@@ -127,4 +127,15 @@ public RingBufferAdmin createRingBufferAdmin() {
     public void setUseThreadLocals(final boolean useThreadLocals) {
         loggerDisruptor.setUseThreadLocals(useThreadLocals);
     }
+
+    /**
+     * Returns the number of logging events discarded by the disruptor's queue full policy, or 0 if the disruptor
+     * does not use a discarding policy or has not discarded.
+     *
+     * @return 0 if the disruptor is not configured to discard or has not discarded, otherwise a positive long
+     */
+    @Override
+    public long getDiscardCount() {
+        return DiscardingAsyncQueueFullPolicy.getDiscardCount(loggerDisruptor.getAsyncQueueFullPolicy());
+    }
 }

log4j-core/src/main/java/org/apache/logging/log4j/core/async/AsyncLoggerDisruptor.java

@@ -86,6 +86,10 @@ WaitStrategy getWaitStrategy() {
         return waitStrategy;
     }
 
+    AsyncQueueFullPolicy getAsyncQueueFullPolicy() {
+        return asyncQueueFullPolicy;
+    }
+
     public String getContextName() {
         return contextName;
     }

log4j-core/src/main/java/org/apache/logging/log4j/core/async/package-info.java

@@ -18,7 +18,7 @@
  * Provides Asynchronous Logger classes and interfaces for low-latency logging.
  */
 @Export
-@Version("2.23.0")
+@Version("2.24.0")
 package org.apache.logging.log4j.core.async;
 
 import org.osgi.annotation.bundle.Export;

log4j-core/src/main/java/org/apache/logging/log4j/core/package-info.java

@@ -18,7 +18,7 @@
  * Implementation of Log4j 2.
  */
 @Export
-@Version("2.20.2")
+@Version("2.21.0")
 package org.apache.logging.log4j.core;
 
 import org.osgi.annotation.bundle.Export;