Unfortunately the documentation for Erlang doesn’t really describe any pros/cons for anything and I’m not an expert in it so I don’t know what the limitations are for the Erlang approach but they certainly must be (e.g. if you have long running sessions and do several upgrades, are you running N versions of the code & eating up RAM because the old sessions aren’t complete?).
As I understand it, Erlang/OTP captures the entire state of the program and it’s a feature of the language and VM to accomplish this. It’s not something you can retrofit into any arbitrary language. For example, your JS app or your Python app or your Rust app won’t be able to do the same easily which means it won’t be robust and it will be error prone. Thus I stand by that there’s no “generic” solution you can bolt onto an arbitrary language.
> if you have long running sessions and do several upgrades, are you running N versions of the code & eating up RAM because the old sessions aren’t complete?
I believe Erlang supports two versions running along each other. They capped it at two because back when this was developed there wasn't enough RAM. Joe Armstrong gave at least one talk where he says if he'd have liked to support arbitrary number of versions and garbage collect them as old sessions complete.
> Thus I stand by that there’s no “generic” solution you can bolt onto an arbitrary language.
The main point of the post is centered around Barbara Liskov saying "maybe we need languages that are a little bit more complete now". I'm not interested in the limitations of current languages, I'm interested in the future possibilities.
> As I understand it, Erlang/OTP captures the entire state of the program and it’s a feature of the language and VM to accomplish this. It’s not something you can retrofit into any arbitrary language. For example, your JS app or your Python app or your Rust app won’t be able to do the same easily which means it won’t be robust and it will be error prone. Thus I stand by that there’s no “generic” solution you can bolt onto an arbitrary language.
I say you can do hotload in any language that supports dlsym/dlopen or eval. I've done it (rather poorly) in Perl and C, and I'm sure others have done it in other languages.
It's a lot nicer in Erlang, so IMHO, if your use case includes long running processes with expensive to construct or transfer state (such as long running sockets), it's worth considering Erlang or something than can do hot loading.
vlovich123|2 years ago
As I understand it, Erlang/OTP captures the entire state of the program and it’s a feature of the language and VM to accomplish this. It’s not something you can retrofit into any arbitrary language. For example, your JS app or your Python app or your Rust app won’t be able to do the same easily which means it won’t be robust and it will be error prone. Thus I stand by that there’s no “generic” solution you can bolt onto an arbitrary language.
stevan|2 years ago
I believe Erlang supports two versions running along each other. They capped it at two because back when this was developed there wasn't enough RAM. Joe Armstrong gave at least one talk where he says if he'd have liked to support arbitrary number of versions and garbage collect them as old sessions complete.
> Thus I stand by that there’s no “generic” solution you can bolt onto an arbitrary language.
The main point of the post is centered around Barbara Liskov saying "maybe we need languages that are a little bit more complete now". I'm not interested in the limitations of current languages, I'm interested in the future possibilities.
toast0|2 years ago
I say you can do hotload in any language that supports dlsym/dlopen or eval. I've done it (rather poorly) in Perl and C, and I'm sure others have done it in other languages.
It's a lot nicer in Erlang, so IMHO, if your use case includes long running processes with expensive to construct or transfer state (such as long running sockets), it's worth considering Erlang or something than can do hot loading.
gregors|2 years ago
https://www.youtube.com/watch?v=IeUF48vSxwI