Wednesday, September 21, 2011

Using custom exception types

A potentially costly item that comes up on automation failure (if you care, which you should) is delegating/triage: who, what, or how to follow up? There’s a need to add value to the product quality knowledge and preserve work that’s already been done, so if you don’t have time to follow up, the team has bigger problems L

Custom exception types are great for this, because they clearly and unambiguously denote problem source. They avoid the synchronization problems, typos, other omissions that logs can have, and become a programmable aspect of product quality. Strong typing means that the compiler is your friend, so a class of implementation problems is found earlier rather than later.

For products that ship to run remotely on client OS’s or in the cloud, they can be configured and turned on or off if performance requires it or information is limited for end-users benefit.

The “is-a” idiom works very well for handlers with an inheritance hierarchy of exception types. For example, suppose the product or project name is “Widget”:

Note too that “oracle” refers to the predictive agent, not the database company.

Each class can have it’s own data, accessors, serialization, constructors etc. Information about a failure is now encapsulated for the thread. The catch(…) clause specification uses the is-a idiom, so can be used to handle these exceptions in an organized way.

If there are other threads in the module or different modules, and they might be blocking on a synchronous communication, they can be interrupted through a back door for the lab environment, and information there encapsulated as well for packaging with the primary thread. This is more reliable than e.g. depending on log timestamp synchronization, although that can work as well.

Tomorrow: more thoughts on packaging and presenting information for humans (manual analysis) and automated processes.

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