70 ms·

Elixir removed a jankier https://www.erlang.org/doc/apps/sasl/appup.html https://www.erlang.org/doc/apps/sasl/appup.html mechanism that defined how state is upg

Elixir removed a jankier https://www.erlang.org/doc/apps/sasl/appup.html https://www.erlang.org/doc/apps/sasl/appup.html mechanism that defined how state is upgraded or downgraded, while watching a directory and recompiling a module automatically or manually from the repl is still common

diggan 1y ago
> while watching a directory and recompiling a module automatically or manually from the repl is still common That makes it sound like the "hot" part has been removed then, and it's just basically a "live reload" rather than "hot code loading", is that right? There is no persistent state and you get a fresh one after the automatic compilation happened?
- elitepleb 1y ago
  queued messages stay around in the mailboxes, so no state is lost, but don't get migrated/transformed/versioned via the appup mechanism, unless you opt back into it via libraries for it like https://github.com/ausimian/castle https://github.com/ausimian/castle
- toast0 1y ago
  I've used utility functions in Erlang where I make changes, then compile and load all modified modules... It's absolutely hot loading, there's persistent state, any fully qualified function calls run in the newest module. The gen_server pattern always calls into your behavior module with fully qualified calls, so those are pretty easy to get into new code at a reasonable time. If you write your own service loop, it's pretty common to call ?MODULE:loop() to enable hotloading there too. There's footguns; hotloading is a way to make rapid changes to your system, but sometimes rapid changes isn't what's needed and sometimes the rapid change you make is to go from a partially broken system to a fully broken system. But, there's a virtuous circle when you can make production changes quickly, because you can make a small change and observe and make many follow ups in a single day. With push processes that take a long time, you end up encouraged to make a bigger change one time, otherwise you spend all day waiting for traffic to move between old and new versions, or waiting for instances to deploy, etc.
- throwawaymaths 1y ago
  no, for example if you are running a liveview in dev and recompiling your code the liveview does not lose its state and jumps into the new module, unless I'm mistaken.

diggan 1y ago

> while watching a directory and recompiling a module automatically or manually from the repl is still common That makes it sound like the "hot" part has been removed then, and it's just basically a "live reload" rather than "hot code loading", is that right? There is no persistent state and you get a fresh one after the automatic compilation happened?

elitepleb 1y ago
queued messages stay around in the mailboxes, so no state is lost, but don't get migrated/transformed/versioned via the appup mechanism, unless you opt back into it via libraries for it like https://github.com/ausimian/castle https://github.com/ausimian/castle
toast0 1y ago
I've used utility functions in Erlang where I make changes, then compile and load all modified modules... It's absolutely hot loading, there's persistent state, any fully qualified function calls run in the newest module. The gen_server pattern always calls into your behavior module with fully qualified calls, so those are pretty easy to get into new code at a reasonable time. If you write your own service loop, it's pretty common to call ?MODULE:loop() to enable hotloading there too. There's footguns; hotloading is a way to make rapid changes to your system, but sometimes rapid changes isn't what's needed and sometimes the rapid change you make is to go from a partially broken system to a fully broken system. But, there's a virtuous circle when you can make production changes quickly, because you can make a small change and observe and make many follow ups in a single day. With push processes that take a long time, you end up encouraged to make a bigger change one time, otherwise you spend all day waiting for traffic to move between old and new versions, or waiting for instances to deploy, etc.
throwawaymaths 1y ago
no, for example if you are running a liveview in dev and recompiling your code the liveview does not lose its state and jumps into the new module, unless I'm mistaken.