Panic handling

There are two types of failures in Rust:

• recoverable errors, using the Result type and the Error trait
• panics, (almost) unrecoverable failures that unwind the stack

It's time to talk about the latter!

Panics

You should trigger a panic when:

• you encounter a situation that you can't recover from
• it would be unsafe to continue
• it's not worth the effort to perform any kind of more sophisticated error handling.

A few examples:

• you're missing a resource that you absolutely need to do your job
• an internal invariant of your application has been violated
• you're in testing code and you don't want to continue if a specific condition is not met

Panics and telemetry

Regardless of the source, you should build a telemetry pipeline that knows how to handle panics.

Whenever a panic is triggered, Rust will start unwinding the stack and will eventually invoke the panic hook for your application.
The default hook will print the panic message to stderr and then abort the process. This may be good enough if you're running your application in a terminal, but it's not going to be very useful if you're running in a production environment: you want the panic information to be captured by the same telemetry pipeline that you're using for everything else.

We need a custom panic hook!

Exercise

The exercise for this section is located in 02_failures/03_panics