default FailureStrategy getFailureStrategy() {
    return FailureStrategy.OPTIMISTIC;
  }
Overrides this method to set the expected FailureStrategy, {@link FailureStrategy#OPTIMISTIC}
is the default strategy.

@return {@link FailureStrategy}
iotdb-api/trigger-api/src/main/java/org/apache/iotdb/trigger/api/Trigger.java