Fixes "InvalidParameterException: Log events in a single PutLogEvents request must be in chronological order." and also a race condition

src/main/java/io/github/dibog/AwsCWEventDump.java

@@ -159,7 +159,7 @@ private LogStream findLogStream(String aGroupName, String aStreamName) {
         return null;
     }
 
-    private void log(Collection<ILoggingEvent> aEvents) {
+    private void log(List<ILoggingEvent> logbackEvents) {
         if(dateFormat!=null) {
             dateHolder.setTime(System.currentTimeMillis());
             String newStreamName = streamName + "-" + dateFormat.format(dateHolder);
@@ -174,9 +174,17 @@ else if (awsLogs==null) {
             closeStream();
             openStream(streamName);
         }
+
+        // Need to sort events by timestamp prior to sending to CloudWatch
+        Collections.sort (logbackEvents, new Comparator<ILoggingEvent>() {
+            @Override
+            public int compare(ILoggingEvent a, ILoggingEvent b) {
+                return Long.compare (a.getTimeStamp(), b.getTimeStamp());
+            }
+        });
 
-        Collection<InputLogEvent> events =  new ArrayList<>(aEvents.size());
-        for(ILoggingEvent event : aEvents) {
+        Collection<InputLogEvent> events =  new ArrayList<>(logbackEvents.size());
+        for(ILoggingEvent event : logbackEvents) {
             if(event.getLoggerContextVO()!=null) {
                 events.add(new InputLogEvent()
                         .withTimestamp(event.getTimeStamp())
@@ -205,23 +213,23 @@ public void queue(ILoggingEvent event) {
     }
 
     public void run() {
-        List<ILoggingEvent> collections = new LinkedList<ILoggingEvent>();
+        List<ILoggingEvent> logbackEvents = new LinkedList<>();
         LoggerContextVO context = null;
         while(!done) {
 
             try {
-                int[] nbs = queue.drainTo(collections);
-                if(context==null && !collections.isEmpty()) {
-                    context = collections.get(0).getLoggerContextVO();
+                int[] nbs = queue.drainTo(logbackEvents);
+                if(context==null && !logbackEvents.isEmpty()) {
+                    context = logbackEvents.get(0).getLoggerContextVO();
                 }
 
                 int msgProcessed = nbs[0];
                 int msgSkipped = nbs[1];
                 if(context!=null && msgSkipped>0) {
-                    collections.add(new SkippedEvent(msgSkipped, context));
+                    logbackEvents.add(new SkippedEvent(msgSkipped, context));
                 }
-                log(collections);
-                collections.clear();
+                log(logbackEvents);
+                logbackEvents.clear();
             }
             catch(InterruptedException e) {
                 // ignoring

src/main/java/io/github/dibog/AwsLogAppender.java

@@ -67,19 +67,19 @@ public void setCreateLogGroup(boolean createLogGroup) {
     }
 
     @Override
-    protected void append(ILoggingEvent event) {
-
-        AwsCWEventDump queue = dump;
-        if (dump != null) {
-            event.prepareForDeferredProcessing();
-            dump.queue(event);
-        }
+    protected synchronized void append(ILoggingEvent event) {
 
+        event.prepareForDeferredProcessing();
+        dump.queue(event);
     }
 
     @Override
-    public void start() {
-        dump = new AwsCWEventDump(this );
+    public synchronized void start() {
+        if (isStarted()) {
+            return;
+        }
+
+        dump = new AwsCWEventDump(this);
 
         Thread t = new Thread(dump);
         t.setDaemon(true);
@@ -89,12 +89,13 @@ public void start() {
     }
 
     @Override
-    public void stop() {
-        super.stop();
-        if(dump!=null) {
-            // flush it
-            dump.shutdown();
+    public synchronized void stop() {
+        if (!isStarted()) {
+            return;
         }
+
+        super.stop();
+        dump.shutdown();
         dump = null;
     }
 }