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I've written an article on error handling some point and ended up with: "An error is when the program is operating outside the intended path of execution." Wha

by gnoack 8y ago

I've written an article on error handling some point and ended up with: "An error is when the program is operating outside the intended path of execution." What counts as intended is a question of definition, but in concrete examples of local reasoning within a function this question is usually easier to answer. Thinking about it in terms of (explicit or implicit) contracts, like Bertrand Meyer, sounds like a smart idea. https://blog.gnoack.org/post/error_handling/ https://blog.gnoack.org/post/error_handling/

jstimpfle 8y ago
> Warning: Textual logging is not an error handling strategy. Logs are not meant for machine consumption so it’s hard to have automated monitoring based on them. I'd beg to disagree. As for the general statement of your post, I like how you're talking about stakeholders and (specification) bounds but I don't think it's an actionable viewpoint. The idea of "Bubbling up errors" inside a program is caught in the software reuse mindset but it's not possible to take action on encountering a true error (here "true" means "outside specifiation"). That's because the state of your whole program is undefined after the encounter. Which means that the best you can do is to call abort() and hope that the program will end with some info for debugging. (Unless we are talking about a VM or sandboxed code, in which case again you could just call some equivalent of abort() from the code inside and "catch" that in the host code and restart the VM or something).
- gbear605 8y ago
  In Java, your true error dichotomy is done using checked versus unchecked exceptions. Checked exceptions can usually be handled while unchecked exceptions usually can’t be, so they aren’t usually caught and instead just bubble all the way up.
- gnoack 8y ago
  Thanks for the feedback. :) To clarify, in the context of the article, "making errors observable from the outside" is not meant at the per-function level, but meant at the level of the whole program, which includes abort(). I should improve the wording there. abort() is perfectly legitimate if you can't recover within the same process. It's not at odds with routing to the right stakeholder, as long as the parent process catches the crash and does appropriate error handling (e.g. "Send a crash report" dialogs or other watchdogs). Regarding textual logging, I'm not sure exactly which part you disagree with. :) I'm aware that people commonly write regex-based extractors, and I've done the same, but having the choice I'd always go for a more schema-ful error reporting channel. That's more lightweight both for reading and for writing it, and avoids a whole class of regex bugs.
  - jstimpfle 8y ago
    OK I had probably skimmed too much but now I think we're just talking about different things here. I like your post, so let's give it another chance: https://news.ycombinator.com/item?id=18390030 https://news.ycombinator.com/item?id=18390030 :-) Regarding textual logging, I think it works wonderfully and I don't think it's at odds with schema-ful reporting. One good way is to include error codes. Informal messages are at least as important. They are ergonomic to humans and their meanings are easy to look up with a web search. Of course textual logging can always be supported by other means, like crash dumps.

by gnoack 8y ago

jstimpfle 8y ago

> Warning: Textual logging is not an error handling strategy. Logs are not meant for machine consumption so it’s hard to have automated monitoring based on them. I'd beg to disagree. As for the general statement of your post, I like how you're talking about stakeholders and (specification) bounds but I don't think it's an actionable viewpoint. The idea of "Bubbling up errors" inside a program is caught in the software reuse mindset but it's not possible to take action on encountering a true error (here "true" means "outside specifiation"). That's because the state of your whole program is undefined after the encounter. Which means that the best you can do is to call abort() and hope that the program will end with some info for debugging. (Unless we are talking about a VM or sandboxed code, in which case again you could just call some equivalent of abort() from the code inside and "catch" that in the host code and restart the VM or something).

gbear605 8y ago
In Java, your true error dichotomy is done using checked versus unchecked exceptions. Checked exceptions can usually be handled while unchecked exceptions usually can’t be, so they aren’t usually caught and instead just bubble all the way up.
gnoack 8y ago
Thanks for the feedback. :) To clarify, in the context of the article, "making errors observable from the outside" is not meant at the per-function level, but meant at the level of the whole program, which includes abort(). I should improve the wording there. abort() is perfectly legitimate if you can't recover within the same process. It's not at odds with routing to the right stakeholder, as long as the parent process catches the crash and does appropriate error handling (e.g. "Send a crash report" dialogs or other watchdogs). Regarding textual logging, I'm not sure exactly which part you disagree with. :) I'm aware that people commonly write regex-based extractors, and I've done the same, but having the choice I'd always go for a more schema-ful error reporting channel. That's more lightweight both for reading and for writing it, and avoids a whole class of regex bugs.
- jstimpfle 8y ago
  OK I had probably skimmed too much but now I think we're just talking about different things here. I like your post, so let's give it another chance: https://news.ycombinator.com/item?id=18390030 https://news.ycombinator.com/item?id=18390030 :-) Regarding textual logging, I think it works wonderfully and I don't think it's at odds with schema-ful reporting. One good way is to include error codes. Informal messages are at least as important. They are ergonomic to humans and their meanings are easy to look up with a web search. Of course textual logging can always be supported by other means, like crash dumps.