> I'm learning Rust by implementing a structured logging API similar to the one found in [Serilog](http://serilog.net).
Log events consist of a format and list of *named* arguments:
```rust
#[macro_use]
extern crate emit;
use std::env;
fn main() {
let _flush = emit::pipeline::init("http://localhost:5341/", None);
emit!("Hello, {}!", name: env::var("USERNAME").unwrap());
}
```
These end up in JSON payloads like:
```json
{
"Timestamp": "2016-03-17T00:17:01Z",
"MessageTemplate": "Hello, {name}!",
"Properties": {
"name": "nblumhardt"
}
}
```
Which can be rendered out to text or searched/sorted/filtered based on the event properties:
I'm using Seq and its JSON format while I design the crate, but like Serilog this should eventually be pluggable to other log collectors and formats.
**What about the `log` crate?**
The `log!()` macros are obviously the best way to capture diagnostic events in Rust as it stands. However, `log` destructively renders events into text:
```rust
info!("Hello, {}!", env::var("USERNAME").unwrap());
```
There's no way for a log processing system to later pull the username value from this message, except through handwritten parsers/regular expressions.
The idea of `emit` is that rendering _can_ happen at any point - but the original values are preserved for easy machine processing as well.