Читать книгу From Traditional Fault Tolerance to Blockchain - Wenbing Zhao - Страница 41

A distributed system usually receives message from, and sends message to, the outside world, such as the clients of the services provided by the distributed system. Once a message is sent to the outside world, the state of the distributed system may be exposed to the outside world. If a failure occurs, the outside world cannot be relied upon for recovery. Therefore, to ensure that the recovered state is consistent with the external view, sufficient recovery information must be logged prior to the sending of a message to the outside world. This is what so called the output commit problem [21].