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You do need to use it, not to handle errors but to avoid it taking down the whole process (and probably sending some logs / alert / monitoring). Which doesn't a
by the_gipsy 2y ago
You do need to use it, not to handle errors but to avoid it taking down the whole process (and probably sending some logs / alert / monitoring). Which doesn't apply everywhere, but at least in web dev it does: if a request / task panics, you want to abort just that, not the whole server including any other requests / tasks running.
Sadly, you need every goroutine to have its own recovery handler. This works well for your general request / task entrypoints, as there should only be one for each kind, but you need to watch out for any third-party libs spawning goroutines without recovery. They will take down your whole server.
- usrbinbash 2y ago> if a request / task panics ...and the condition why it panics is not a situation that warrants a crash, then whatever is called upon handling that request is issueing a panic when it shouldn't. The reason why some libs do that anyway is exactly what I describe above: because in many peoples minds panic == exception. That's a logic error in the code and should get fixed. And one of the best ways to make devs fix things, is to let their application crash when something that shouldn't happen happens anyway, because then someone will start complaining why a service is unreachable. TL;DR: If some condition shouldn't crash a process, it has no earthly business causing a panic.
- the_gipsy 2y agoYou're conflating unnecessary panics, with how to handle panics. There will always be panics. You don't need to crash the thing to make devs notice, they're not idiots no matter what Rob Pike told you. You can alert and not throw out the baby with the bathwater. Nobody wants panics in their code, even if they're not crashing the whole world.
- usrbinbash 2y ago> You're conflating unnecessary panics, with how to handle panics. I don't think so. If I have to handle a panic, because otherwise my program no longer works, one of 2 things is true in the vast majority of cases: - There is something seriously wrong with the program or its environment, causing it to panic - There is something in the program issueing a panic when really it should return an error In short: there should be no need to "handle panics" Panics are irrecoverable conditions where its preferable for the program to crash rather than continue. If code panicks for any other reason, thats, in my opinion, wrong, and should be fixed. Panics are not the equivalent to exceptions, and error returns exist for a reason. People who don't like that paradigm can always use a language that uses the exception-paradigm.
- the_gipsy 2y ago> People who don't like that paradigm can always use a language that uses the exception-paradigm. FYI the go std library recovers from panics when it spawns goroutines internally, in most cases. All this has next to nothing to do with exceptions. Nobody is saying to use panics to pass errors or any control flow.
- gizzlon 2y agoThat's not my experience. Other then the recover included in the http lib, I don't think I have ever used recover. Why is you code panic'in? I would let it take down the process and figure out why. I have had backend programs set up to automatically restart, which can be useful. But I would treat any panic as a big deal.
- the_gipsy 2y agoYou can treat panics as a big deal, and not necessarily kill the whole program. It's not mutually exclusive. For example, at my work, we have some nightly long running tasks. We don't panic every day. But from time to time, let's say once or twice per month, some code changes cause a panic. On that day, we don't want to kill the long running tasks for no good reason other than somehow indirectly making someone fix the panic. We have alerts for that, and we're all grownups.
- usrbinbash 2y ago> You can treat panics as a big deal, and not necessarily kill the whole program. It's not mutually exclusive. Yes it is mutually exclusive. Something that doesn't kill the program, aka a recoverable ERROR CONDITION should not cause a panic, that's not what panics exist for. Something that causes a panic without using the `panic` keyword, like an out-of-bounds read, nil-derference, etc. is indicative of a serious problem that should be fixed before the program is allowed to run again.
- the_gipsy 2y ago> Something that doesn't kill the program, aka a recoverable ERROR CONDITION should not cause a panic Can you explain why? > a serious problem that should be fixed before the program is allowed to run again Can you explain why the program should not be allowed to run again? Is this some sort of software spiritualism?
- mjevans 2y agoIt indicates that either programmer or at least operator (if E.G. this is a critical data validation fail), some sort of human, intervention is required. The situation must be evaluated critically before any further work occurs.