diff --git a/flume-ng-sources/flume-taildir-source/src/main/java/org/apache/flume/source/taildir/ReliableTaildirEventReader.java b/flume-ng-sources/flume-taildir-source/src/main/java/org/apache/flume/source/taildir/ReliableTaildirEventReader.java
index ae9583620a..b4ca0cb1f5 100644
--- a/flume-ng-sources/flume-taildir-source/src/main/java/org/apache/flume/source/taildir/ReliableTaildirEventReader.java
+++ b/flume-ng-sources/flume-taildir-source/src/main/java/org/apache/flume/source/taildir/ReliableTaildirEventReader.java
@@ -22,7 +22,6 @@
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.Lists;
-import com.google.common.collect.Maps;
 import com.google.common.collect.Table;
 import com.google.gson.stream.JsonReader;
 import org.apache.flume.Event;
@@ -43,6 +42,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
+import java.util.concurrent.ConcurrentHashMap;
 
 @InterfaceAudience.Private
 @InterfaceStability.Evolving
@@ -53,7 +53,7 @@ public class ReliableTaildirEventReader implements ReliableEventReader {
   private final Table<String, String, String> headerTable;
 
   private TailFile currentFile = null;
-  private Map<Long, TailFile> tailFiles = Maps.newHashMap();
+  private Map<Long, TailFile> tailFiles = new ConcurrentHashMap<>();
   private long updateTime;
   private boolean addByteOffset;
   private boolean cachePatternMatching;
diff --git a/flume-ng-sources/flume-taildir-source/src/main/java/org/apache/flume/source/taildir/TaildirSource.java b/flume-ng-sources/flume-taildir-source/src/main/java/org/apache/flume/source/taildir/TaildirSource.java
index 9ecccd7487..c450c8852c 100644
--- a/flume-ng-sources/flume-taildir-source/src/main/java/org/apache/flume/source/taildir/TaildirSource.java
+++ b/flume-ng-sources/flume-taildir-source/src/main/java/org/apache/flume/source/taildir/TaildirSource.java
@@ -25,6 +25,7 @@
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -81,7 +82,7 @@ public class TaildirSource extends AbstractSource implements
   private int writePosInterval;
   private boolean cachePatternMatching;
 
-  private List<Long> existingInodes = new CopyOnWriteArrayList<Long>();
+  private List<Long> existingInodes = new ArrayList<>();
   private List<Long> idleInodes = new CopyOnWriteArrayList<Long>();
   private Long backoffSleepIncrement;
   private Long maxBackOffSleepInterval;
@@ -231,9 +232,12 @@ protected SourceCounter getSourceCounter() {
   public Status process() {
     Status status = Status.BACKOFF;
     try {
-      existingInodes.clear();
-      existingInodes.addAll(reader.updateTailFiles());
-      for (long inode : existingInodes) {
+      final List<Long> updatedInodes = reader.updateTailFiles();
+      synchronized (existingInodes) {
+        existingInodes.clear();
+        existingInodes.addAll(updatedInodes);
+      }
+      for (long inode : updatedInodes) {
         TailFile tf = reader.getTailFiles().get(inode);
         if (tf.needTail()) {
           boolean hasMoreLines = tailFileProcess(tf, true);
@@ -304,10 +308,10 @@ private void closeTailFiles() throws IOException, InterruptedException {
       if (tf.getRaf() != null) { // when file has not closed yet
         tailFileProcess(tf, false);
         tf.close();
+        idleInodes.remove(inode);
         logger.info("Closed file: " + tf.getPath() + ", inode: " + inode + ", pos: " + tf.getPos());
       }
     }
-    idleInodes.clear();
   }
 
   /**
@@ -346,10 +350,8 @@ private void writePosition() {
     FileWriter writer = null;
     try {
       writer = new FileWriter(file);
-      if (!existingInodes.isEmpty()) {
-        String json = toPosInfoJson();
-        writer.write(json);
-      }
+      String json = toPosInfoJson();
+      writer.write(json);
     } catch (Throwable t) {
       logger.error("Failed writing positionFile", t);
       sourceCounter.incrementGenericProcessingFail();
@@ -366,9 +368,11 @@ private void writePosition() {
   private String toPosInfoJson() {
     @SuppressWarnings("rawtypes")
     List<Map> posInfos = Lists.newArrayList();
-    for (Long inode : existingInodes) {
-      TailFile tf = reader.getTailFiles().get(inode);
-      posInfos.add(ImmutableMap.of("inode", inode, "pos", tf.getPos(), "file", tf.getPath()));
+    synchronized (existingInodes) {
+      for (long inode : existingInodes) {
+        TailFile tf = reader.getTailFiles().get(inode);
+        posInfos.add(ImmutableMap.of("inode", inode, "pos", tf.getPos(), "file", tf.getPath()));
+      }
     }
     return new Gson().toJson(posInfos);
   }