@Override
  public String toString() {
    return this.mode;
  }
This defines the logical mode of a taskInstance.
Active is the defacto mode for a task, i.e., tasks processing input, reading/writing state, producing output, etc.
Standby is the mode for tasks, that maintain warmed-up KV state by reading from its changelog.
samza-api/src/main/java/org/apache/samza/job/model/TaskMode.java