When logging when is an error fatal?

Question

In logging frameworks like log4j & log4net you have the ability to log various levels of information. Most of the levels have obvious intentions (such as what a \"Debug\" lo

Answer 1

To make this answer short and sweet, if your application crashes, I would consider that fatal. If you cannot connect to an important resource such as a database or a required service, that would be fatal. Overall, I would say that if it keeps your application from running correctly and affects the user, I would classify it as a fatal error.

But the most important way to classify errors is to consistently follow a rule of thumb such as rule 69 in C++ Coding Standards:

"Develop a practical, consistent, and rational error handling policy early in design, and then stick to it."

Answer 2

An error is Fatal if something is missing or a situation occurs for which the application can simply not continue. Possible examples are a missing required config.file or when an exception 'bubbles up' and is caught by an unhandled exception handler

Answer 3

I would use fatal if my next step is for the application to terminate, or merely not do any more subsequent work. If the application is part of a batch or there are multiple processes running, this can be useful for tracing what happened.

If there is a chance of recovery (e.g., loss of network connection with retries for a while) I would not use a fatal.

If I have multiple service threads activated by a main thread and one of them fails because of some bad input but the application can still serve new requests, I do not consider it fatal.

Answer 4

I consider fatal errors to be when your application can't do any more useful work. Non-fatal errors are when there's a problem but your application can still continue to function, even at a reduced level of functionality or performance.

Examples of fatal errors include:

• Running out of disk space on the logging device and you're required to keep logging.
• Total loss of network connectivity in a client application.
• Missing configuration information if no default can be used.

Non-fatal errors would include:

• A server where a single session fails for some reason but you can still service other clients.
• An intermittent error, such as lost session, if a new session can be established.
• Missing configuration information if a default value can be used.