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Comment by evercast | Hacker News Reader

I believe the idea is that 'panic' is considered something fatal. If it happens, the application should die unless you have a strong reason for it not to. If you can recover e.g. by returning HTTP 500 for a single request, it should be handled by returning errors up throughout the call stack, i.e., by error handling instead of panicking.

It's definitely an opinionated approach though.

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Nil pointer panics happen. When a DB column that was supposed to be non-null is null and the code unexpectedly accesses it. Oh schema won't help because legacy. There are rare though and we fix such issues as they are discovered, but just pointing out a benign case when crashing the whole server on panic may be a wrong approach. Our approach is to always recover from panics so the server keeps chugging, but raise an alarm so someone is paged and fixes the issue right away.

> I believe the idea is that 'panic' is considered something fatal.

I think opinions in 3rd party Go code on what “fatal” means vary, that’s the issue. Sure it was intended to mean “this error is so bad the entire program needs to die right now” but in practice there’s cases where it’s treated more like an unchecked exception in Java, i.e., “I can’t recover from this so _I’m_ going to give up but _you_ can keep going.” Or put another way, what a library might consider fatal the caller doesn’t. It can be argued whether or not that’s the right thing to do, but the fact is it happens in the wild, so for something like a server you probably should trap it.

> but in practice there’s cases where it’s treated more like an unchecked exception in Java, i.e., “I can’t recover from this so _I’m_ going to give up but _you_ can keep going.”

Java has a supertype for unrecoverable problems like out-of-memory-errors. It's called "Error", a subtype from Throwable. Exceptions are also Throwables, but they are NOT errors.

There's nothing unrecoverable about Error exceptions. If one thread hit a bug and threw StackOverflowError, it's not a reason to kill the entire application or even thread itself, just unwind stack, show some error and continue processing next task. The only tricky situation I'm aware of is OutOfMemoryError, because it can affect other threads. I'd prefer to restart the server. But again it's just because typical code allocated heap all the time. One can write code carefully without heap allocations and this code will work just fine with OOM errors thrown around.

> It can be argued whether or not that’s the right thing to do

No, because both approaches could be right at a higher level, to pretake that decision at this level is definitely wrong here?!

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