Failure semantics

In distributed computing, failure semantics is used to describe and classify errors that distributed systems can experience.^[1][2]

Types of errors

A list of types of errors that can occur:

• An omission error is when one or more responses fails.
• A crash error is when nothing happens. A crash is a special case of omission when all responses fails.
• A Timing error is when one or more responses arrive outside the time interval specified. Timing errors can be early or late. An omission error is a timing error when a response has infinite timing error.
• An arbitrary error is any error, (i.e. a wrong value or a timing error).
• When a client uses a server it can cope with different type errors from the server.
  • If it can manage a crash at the server it is said to assume the server to have crash failure semantics.
  • If it can manage a service omission it is said to assume the server to have omission failure semantics.
    • Failure semantics are the type of errors are expected to appear.
• Should another type of error appear it will lead to a service failure because it cannot be managed.

References

1. Flaviu Christian, Understanding Fault-Tolerant Distributed Systems
2. Arno Puder; Kay Romer; Frank Pilhofer (2005). Distributed Systems Architecture. Morgan Kaufmann. ISBN 1558606483., pp 14–16.