Merge pull request pinterest#106 from yyejun/fix_writer_delete

Fix a race condition when two upload happens at the same time

src/main/java/com/pinterest/secor/uploader/Uploader.java

@@ -102,15 +102,15 @@ private void uploadFiles(TopicPartition topicPartition) throws Exception {
             topicPartition.getTopic(),
             topicPartition.getPartition());
 
-        // Deleting writers closes their streams flushing all pending data to the disk.
-        mFileRegistry.deleteWriters(topicPartition);
         mZookeeperConnector.lock(lockPath);
         try {
             // Check if the committed offset has changed.
             long zookeeperComittedOffsetCount = mZookeeperConnector.getCommittedOffsetCount(
                     topicPartition);
             if (zookeeperComittedOffsetCount == committedOffsetCount) {
                 LOG.info("uploading topic {} partition {}", topicPartition.getTopic(), topicPartition.getPartition());
+                // Deleting writers closes their streams flushing all pending data to the disk.
+                mFileRegistry.deleteWriters(topicPartition);
                 Collection<LogFilePath> paths = mFileRegistry.getPaths(topicPartition);
                 List<Future<?>> uploadFutures = new ArrayList<Future<?>>();
                 for (LogFilePath path : paths) {