- Ensure that rollback instant is always created before the next commit instant.

This especially affects IncrementalPull for MOR tables since we can end up pulling in
  log blocks for uncommitted data
- Ensure that generated commit instants are 1 second apart

hudi-common/src/main/java/org/apache/hudi/common/table/timeline/HoodieActiveTimeline.java

@@ -28,6 +28,7 @@ import java.util.Arrays;
 import java.util.Date;
 import java.util.HashSet;
 import java.util.Set;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Function;
 import java.util.stream.Stream;
 import org.apache.hadoop.fs.FSDataInputStream;
@@ -66,12 +67,21 @@ public class HoodieActiveTimeline extends HoodieDefaultTimeline {
 
   private static final transient Logger log = LogManager.getLogger(HoodieActiveTimeline.class);
   protected HoodieTableMetaClient metaClient;
+  private static AtomicReference<String> lastInstantTime = new AtomicReference<>(String.valueOf(Integer.MIN_VALUE));
 
   /**
    * Returns next commit time in the {@link #COMMIT_FORMATTER} format.
+   * Ensures each commit time is atleast 1 second apart since we create COMMIT times at second granularity
    */
   public static String createNewCommitTime() {
-    return HoodieActiveTimeline.COMMIT_FORMATTER.format(new Date());
+    lastInstantTime.updateAndGet((oldVal) -> {
+      String newCommitTime = null;
+      do {
+        newCommitTime = HoodieActiveTimeline.COMMIT_FORMATTER.format(new Date());
+      } while (HoodieTimeline.compareTimestamps(newCommitTime, oldVal, LESSER_OR_EQUAL));
+      return newCommitTime;
+    });
+    return lastInstantTime.get();
   }
 
   protected HoodieActiveTimeline(HoodieTableMetaClient metaClient, Set<String> includedExtensions) {
@@ -99,7 +109,8 @@ public class HoodieActiveTimeline extends HoodieDefaultTimeline {
    *
    * @deprecated
    */
-  public HoodieActiveTimeline() {}
+  public HoodieActiveTimeline() {
+  }
 
   /**
    * This method is only used when this object is deserialized in a spark executor.
@@ -112,7 +123,6 @@ public class HoodieActiveTimeline extends HoodieDefaultTimeline {
 
   /**
    * Get all instants (commits, delta commits) that produce new data, in the active timeline *
-   *
    */
   public HoodieTimeline getCommitsTimeline() {
     return getTimelineOfActions(Sets.newHashSet(COMMIT_ACTION, DELTA_COMMIT_ACTION));
@@ -139,7 +149,7 @@ public class HoodieActiveTimeline extends HoodieDefaultTimeline {
   /**
    * Get only pure commits (inflight and completed) in the active timeline
    */
-  public HoodieTimeline   getCommitTimeline() {
+  public HoodieTimeline getCommitTimeline() {
     return getTimelineOfActions(Sets.newHashSet(COMMIT_ACTION));
   }
 
@@ -258,7 +268,9 @@ public class HoodieActiveTimeline extends HoodieDefaultTimeline {
     return readDataFromPath(detailPath);
   }
 
-  /** BEGIN - COMPACTION RELATED META-DATA MANAGEMENT **/
+  /**
+   * BEGIN - COMPACTION RELATED META-DATA MANAGEMENT
+   **/
 
   public Option<byte[]> getInstantAuxiliaryDetails(HoodieInstant instant) {
     Path detailPath = new Path(metaClient.getMetaAuxiliaryPath(), instant.getFileName());