First implementation of Async append blocking until an optional timeout

See logfellow#559

pom.xml

@@ -211,6 +211,12 @@
             <version>${org.mockito.version}</version>
             <scope>test</scope>
         </dependency>
+<dependency>
+    <groupId>org.awaitility</groupId>
+    <artifactId>awaitility</artifactId>
+    <version>4.1.0</version>
+    <scope>test</scope>
+</dependency>
     </dependencies>
 
     <build>

src/main/java/net/logstash/logback/appender/AsyncDisruptorAppender.java

@@ -19,16 +19,20 @@
 import java.util.Arrays;
 import java.util.Formatter;
 import java.util.List;
+import java.util.Objects;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledThreadPoolExecutor;
 import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicLong;
+import java.util.concurrent.locks.LockSupport;
 
 import ch.qos.logback.core.status.OnConsoleStatusListener;
 import ch.qos.logback.core.status.Status;
+import ch.qos.logback.core.util.Duration;
+
 import net.logstash.logback.appender.listener.AppenderListener;
 import ch.qos.logback.access.spi.IAccessEvent;
 import ch.qos.logback.classic.AsyncAppender;
@@ -250,6 +254,41 @@ public abstract class AsyncDisruptorAppender<Event extends DeferredProcessingAwa
      */
     protected final List<Listener> listeners = new ArrayList<>();
 
+    public enum AsyncMode {
+        /**
+         * Appender thread is blocked until space is available in the ring buffer
+         * or the retry timeout expires.
+         */
+        BLOCK,
+
+        /**
+         * Event is dropped when the ring buffer is full
+         */
+        DROP
+    }
+    private AsyncMode asyncMode = AsyncMode.DROP;
+
+    /**
+     * Delay (in millis) between consecutive attempts to append an event in the ring buffer when full.
+     * Applicable only when {@link #asyncMode} is set to {@link AsyncMode#DROP}.
+     */
+    private long retryMillis = 100;
+
+    /**
+     * Maximum time to wait for space in the ring buffer before dropping the event.
+     * Applicable only when {@link #asyncMode} is set to {@link AsyncMode#DROP}.
+     * 
+     * <p>Use {@code -1} for no timeout, i.e. block until space is available.
+     */
+    private Duration retryTimeout = Duration.buildByMilliseconds(1000);
+
+    /**
+     * How long to wait for in-flight events during shutdown.
+     */
+    private Duration shutdownGracePeriod = Duration.buildByMinutes(1);
+
+
+
     /**
      * Event wrapper object used for each element of the {@link RingBuffer}.
      */
@@ -422,57 +461,141 @@ public void stop() {
         if (!super.isStarted()) {
             return;
         }
+
         /*
          * Don't allow any more events to be appended.
          */
         super.stop();
+
+
+        /*
+         * Shutdown disruptor and executorService
+         */
+        boolean errorDuringShutdown = false;
+        long remainingTime = Math.max(0, getShutdownGracePeriod().getMilliseconds());
+        long startTime = System.currentTimeMillis();
+
         try {
-            this.disruptor.shutdown(1, TimeUnit.MINUTES);
+            this.disruptor.shutdown(remainingTime, TimeUnit.MILLISECONDS);
         } catch (TimeoutException e) {
-            addWarn("Some queued events have not been logged due to requested shutdown");
+            errorDuringShutdown = true;
         }
 
         this.executorService.shutdown();
 
         try {
-            if (!this.executorService.awaitTermination(1, TimeUnit.MINUTES)) {
-                addWarn("Some queued events have not been logged due to requested shutdown");
+            remainingTime = Math.max(0, remainingTime - (System.currentTimeMillis() - startTime));
+            if (!this.executorService.awaitTermination(remainingTime, TimeUnit.MILLISECONDS)) {
+                errorDuringShutdown = true;
             }
         } catch (InterruptedException e) {
-            addWarn("Some queued events have not been logged due to requested shutdown", e);
+            errorDuringShutdown = true;
         }
+
+        if (errorDuringShutdown) {
+            addWarn("Some queued events have not been logged due to requested shutdown");
+        }
+
+
+        /*
+         * Notify listeners
+         */
         fireAppenderStopped();
     }
 
+
     @Override
     protected void append(Event event) {
         long startTime = System.nanoTime();
+
         try {
             prepareForDeferredProcessing(event);
         } catch (RuntimeException e) {
-            addWarn("Unable to prepare event for deferred processing.  Event output might be missing data.", e);
+            addWarn("Unable to prepare event for deferred processing. Event output might be missing data.", e);
         }
 
-        if (!this.disruptor.getRingBuffer().tryPublishEvent(this.eventTranslator, event)) {
-            long consecutiveDropped = this.consecutiveDroppedCount.incrementAndGet();
-            if ((consecutiveDropped) % this.droppedWarnFrequency == 1) {
-                addWarn("Dropped " + consecutiveDropped + " events (and counting...) due to ring buffer at max capacity [" + this.ringBufferSize + "]");
-            }
-            fireEventAppendFailed(event, RING_BUFFER_FULL_EXCEPTION);
-        } else {
-            long endTime = System.nanoTime();
+        if (enqueueEvent(event)) {
+            // Enqueue success - notify if we had errors previously
+            //
             long consecutiveDropped = this.consecutiveDroppedCount.get();
             if (consecutiveDropped != 0 && this.consecutiveDroppedCount.compareAndSet(consecutiveDropped, 0L)) {
                 addWarn("Dropped " + consecutiveDropped + " total events due to ring buffer at max capacity [" + this.ringBufferSize + "]");
             }
-            fireEventAppended(event, endTime - startTime);
+
+            // Notify parties
+            //
+            fireEventAppended(event, System.nanoTime() - startTime);
+
+        } else {
+            // Log a warning status about the failure
+            //
+            long consecutiveDropped = this.consecutiveDroppedCount.incrementAndGet();
+            if ((consecutiveDropped % this.droppedWarnFrequency) == 1) {
+                addWarn("Dropped " + consecutiveDropped + " events (and counting...) due to ring buffer at max capacity [" + this.ringBufferSize + "]");
+            }
+
+            // Notify parties
+            //
+            fireEventAppendFailed(event, RING_BUFFER_FULL_EXCEPTION);
         }
     }
 
     protected void prepareForDeferredProcessing(Event event) {
         event.prepareForDeferredProcessing();
     }
 
+    /**
+     * Enqueue the given {@code event} in the ring buffer according to the configured {@link #asyncMode}.
+     * 
+     * @param event the {@link Event} to enqueue
+     * @return {@code true} when the even is successfully enqueued in the ring buffer
+     */
+    protected boolean enqueueEvent(Event event) {
+        if (this.asyncMode == AsyncMode.BLOCK) {
+            return enqueueEventBlock(event);
+        } else {
+            return enqueueEventDrop(event);
+        }
+    }
+
+    /**
+     * Enqueue the given {@code event} in the ring buffer, blocking until enough space
+     * is available or the {@link #retryTimeout} expires (if configured).
+     * 
+     * @param event the {@link Event} to enqueue
+     * @return {@code true} when the even is successfully enqueued in the ring buffer
+     */
+    private boolean enqueueEventBlock(Event event) {
+        long timeout = this.retryTimeout.getMilliseconds() <= 0 ? Long.MAX_VALUE : System.currentTimeMillis() + this.retryTimeout.getMilliseconds();
+
+        while (isStarted() && !this.disruptor.getRingBuffer().tryPublishEvent(this.eventTranslator, event)) {
+            // Check for timeout
+            //
+            if (System.currentTimeMillis() >= timeout) {
+                return false;
+            }
+
+            // Wait before retry
+            //
+            long waitDuration = Math.min(this.retryMillis, System.currentTimeMillis() - timeout);
+            if (waitDuration > 0) {
+                LockSupport.parkNanos(waitDuration * 1_000_000L);
+            }
+        }
+
+        return true;
+    }
+
+    /**
+     * Attempt to enqueue the given {@code event} in the ring buffer without blocking. Drop the event
+     * if the ring buffer is full.
+     * 
+     * @param event the {@link Event} to enqueue
+     * @return {@code true} when the even is successfully enqueued in the ring buffer
+     */
+    private boolean enqueueEventDrop(Event event) {
+        return this.disruptor.getRingBuffer().tryPublishEvent(this.eventTranslator, event);
+    }
 
     protected String calculateThreadName() {
         List<Object> threadNameFormatParams = getThreadNameFormatParams();
@@ -581,6 +704,34 @@ public void setWaitStrategyType(String waitStrategyType) {
         setWaitStrategy(WaitStrategyFactory.createWaitStrategyFromString(waitStrategyType));
     }
 
+    public AsyncMode getAsyncMode() {
+        return asyncMode;
+    }
+    public void setAsyncMode(AsyncMode asyncMode) {
+        this.asyncMode = asyncMode;
+    }
+
+    public long getRetryMillis() {
+        return retryMillis;
+    }
+    public void setRetryMillis(long retryMillis) {
+        this.retryMillis = retryMillis;
+    }
+
+    public Duration getRetryTimeout() {
+        return retryTimeout;
+    }
+    public void setRetryTimeout(Duration retryTimeout) {
+        this.retryTimeout = Objects.requireNonNull(retryTimeout);
+    }
+
+    public void setShutdownGracePeriod(Duration shutdownGracePeriod) {
+        this.shutdownGracePeriod = Objects.requireNonNull(shutdownGracePeriod);
+    }
+    public Duration getShutdownGracePeriod() {
+        return shutdownGracePeriod;
+    }
+
     public ThreadFactory getThreadFactory() {
         return threadFactory;
     }