Event data
An event’s attributes describe the data captured when that event occurs. The
generated event method receives one typed argument for each attribute, in
declaration order.
Data types
The scalar types are:
| YAML type | Value |
|---|---|
bool | true or false |
u8, u16, u32, u64 | Unsigned integers of the indicated width |
i8, i16, i32, i64 | Signed integers of the indicated width |
f32, f64 | Floating-point numbers of the indicated width |
string | Text |
uuid | A universally unique identifier |
Types can also be composed or refer to generated types:
| YAML type | Value |
|---|---|
{ option: T } | A value of type T that may be absent |
{ list: T } | An ordered collection of values of type T |
| A record name | An instance of that record |
dynamic | String-keyed values whose names and types are chosen at runtime |
ref | A reference to any entity instance |
Semantic modules add more specific reference forms. These are introduced with targeted references, scoped references, and resources.
YAML model
quent: alpha
model: event_data
entities:
Task:
events:
started:
attributes:
enabled: bool
byte: u8
short_count: u16
attempt: u32
item_count: u64
small_offset: i8
short_offset: i16
offset: i32
large_offset: i64
ended:
attributes:
ratio: f32
score: f64
message: string
run_id: uuid
retry_after: { option: u64 }
tags: { list: string }
extra: dynamic
Instrumentation API
The generated API maps each YAML type to the corresponding type in the selected
programming language. Options, lists, records, and references remain typed.
dynamic is the exception: it deliberately accepts values whose names and
types are determined at runtime.
// SPDX-FileCopyrightText: Copyright (c) 2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
// SPDX-License-Identifier: Apache-2.0
#[allow(unused, clippy::too_many_arguments)]
mod instrumentation {
include!(concat!(env!("OUT_DIR"), "/event_data.rs"));
}
use instrumentation::{Context, DynamicAttributes, EventData, Noop, Task, Uuid};
fn main() -> Result<(), Box<dyn std::error::Error>> {
let context = Context::<EventData>::try_new(Noop)?;
let mut task = context.observer::<Task>().handle();
task.started(true, 1, 2, 3, 4, -1, -2, -3, -4)?;
let mut extra = DynamicAttributes::new();
extra.add("worker", "alpha");
extra.add("queue_depth", 3_u64);
task.ended(
0.5,
0.95,
"complete".to_owned(),
Uuid::now_v7(),
None,
vec!["batch".to_owned(), "priority".to_owned()],
extra,
)?;
Ok(())
}
Key point
Event attributes produce typed parameters in the generated instrumentation API.