@Override
  public void addMissingChildRegion(String childFullPath) {
    synchronized (lock) {
      if (!missingChildren.contains(childFullPath)) {
        missingChildren.add(childFullPath);
      }
    }
  }
@param region the region that owns this logger instance
geode-core/src/main/java/org/apache/geode/internal/cache/partitioned/colocation/SingleThreadColocationLogger.java