# Rustler Logger
[Documentation](https://docs.rs/rustler_logger/latest/rustler_logger/)
`rustler` provides fairly seamless integration between Rust and Elixir.
However, Rust NIFs aren't really integrated with Elixir's logging infrastructure.
This crate provides a set of macros that can be used to log messages directly to the Elixir logger.
### Features
- a `log_to_elixir` attribute macro that wraps functions with code that captures the Elixir environment to send logs
- a `log!` macro to actually emit log messages
- convenience macros for each log level (i.e. `debug!`, `info!`, etc.)
- "keyword argument"-style arguments to set logging metadata
- a panic handler that sends a message with panic information to Elixir
### Usage
```elixir
use rustler::{nif, Env, Term};
use rustler_logger::*;
#[nif]
#[log_to_elixir]
fn show_off_logging() {
info!(
"Hello, ~p! ~p items on your list labeled ~p", // erlang-style format string
"world", 42, "TODO", // format arguments
user="bob", answer=420/10 // metadata
);
// all of the log levels
debug!("convenience");
info!("macros");
notice!("for");
warn!("each");
error!("log");
critical!("level");
alert!("are");
emergency!("available");
// If you need to select a level programmatically, you can use the `log!`
// macro with a level argument.
let log_level = LogLevel::Debug;
log!(log_level, "This is a {} message", log_level.as_str());
}
// This is necessary to load the panic hook.
fn load(_env: Env, _term: Term) -> bool {
log_init();
true
}
rustler::init!("Elixir.Your.Module", load = load);
```
### Troubleshooting & Gotchas
Failing to initialize the logger can cause panic messages to not be emitted.
Failing to wrap functions with `log_to_elixir` can cause log messages to not be emitted.