Pattern for Fault Tolerant Software

Chapter 5. Detection Patterns

The first phase of fault tolerance is detection

The dimensions of detection

A Priori Detection

use constraints

System states, Result, Side effects

If nothing is known about the range of results this method will obviously not work.

Comparing Redundant Results

Redundancy ( 3 , chapter 4)

The value to be compared or The context to enable the identification of the faulty component

To learn about correct system behavior

ex) Bayesian learning technique

Just determining that one is incorrect is helpful,

but insufficient to fix the fault andprevent a failure from occurring

Detect an Error > Detect a failure

The error is detected automatically and corrected before it becomes a failure

‘fail-silent’ and crash failure mode

element stops without informing them that it is stopping

detecting that an element has stopped functioning vsdetermining if an element has stopped operating correctly

Test function return codes

try/catch

Detecting Errors

Next - Fault Correlation