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Comment by preseinger | Hacker News Reader

`panic` is not equivalent to `return err`. It expresses a much more fundamental problem than an error return, and subverts the ability of the reader to model execution control flow. `panic` should essentially never be used in application code, and when it is used it should almost always immediately terminate the program.

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Programming is a vast field, "essentially never" is quite a strong statement.

For many errors, in many situations, terminating the process is quite reasonable.

In my particular situation, the greater system will restart failed processes, and retry failed tasks. I find this useful as in many cases my program can just die when something weird happens, simplifying it's own logic.

This represents a false economy, or maybe a local optimum. It's lovely that your code can be simple in the sense that it can assume all kinds of invariants that, if violated, will simply terminate the execution, which can safely be assumed to start up again anew. But it's decidedly not lovely that you can no longer predict what effect an input will have on your code, and can't effectively reason about, well, anything beyond a trivial lifetime/callstack. If your process dies whenever something weird happens, it effectively becomes nondeterministic -- your greater system model has to assume it can die at any instant for any reason.

> your greater system model has to assume it can die at any instant for any reason

Correct. This is something I have to design for in the system anyway, because in practice anything can (and does!) die at unpredictable times. It's typically an inevitable fact of life that a machine/kernel/program will occasionally die, and your system has to survive that.

Of course it can, but the question is what this sort of termination represents. Hopefully, it represents a serious showstopper bug that gets fixed immediately! If your program is built such that call stacks don't have reasonably deterministic behavior, it's essentially impossible to build a usable model of the program as a maintainer.

I mostly agree, but I’m also comfortable using “panic” in an HTTP server to throw 500’s.

Goodness, I hope not! This breaks all your downstream middleware and whatever business logic is invoked by your handlers. If you encounter a 500-worthy problem it's an `error` return like anything else.

`panic` is not for business logic.

> `panic` is not for business logic.

Neither are 500 responses. A perfect HTTP server never responds 500 and there aren't any situations I've ever encountered where there's any valuable error recovery or business logic left to be done once the server has run into a 500-worthy issue.

IIRC, the HTTP server in the Go standard library recovers panics and issues 500 responses, which is what I would expect it to do.

500 maps to a set of business logic errors, sure. Why not?

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