private boolean isSnapshotCompleted(SnapshotDescription snapshot) throws IOException {
    try {
      final Path snapshotDir = SnapshotDescriptionUtils.getCompletedSnapshotDir(snapshot, rootDir);
      FileSystem fs = master.getMasterFileSystem().getFileSystem();
      // check to see if the snapshot already exists
      return fs.exists(snapshotDir);
    } catch (IllegalArgumentException iae) {
      throw new UnknownSnapshotException("Unexpected exception thrown", iae);
    }
  }
Check to see if the snapshot is one of the currently completed snapshots Returns true if the
snapshot exists in the "completed snapshots folder".
@param snapshot expected snapshot to check
@return <tt>true</tt> if the snapshot is stored on the {@link FileSystem}, <tt>false</tt> if is
        not stored
@throws IOException              if the filesystem throws an unexpected exception,
@throws IllegalArgumentException if snapshot name is invalid.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/snapshot/SnapshotManager.java