Traces

• Unique Trace IDs for 1 user action
  • shared across multiple services

Spans

• Resource Attributes
  • shared by spans in a service
• Span Attributes
  • High Cardinality data for each span.
• Events
  • Gives us timing, and details inside the span

Sampling

• We don't want traces for all events
  • That'd be expensive $$$$$$$$$$
• Sample rate should be representative of out users

Trace Headers

traceparent & tracestate

traceparent: 00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01
             │  │                                │                │
version ◄────┘  │                                │                │
trace-id ◄──────┘                                │                │
parent-id  ◄─────────────────────────────────────┘                │
trace-flags (01 = sampled) ◄──────────────────────────────────────┘

tracestate: key=value,vendorname1=opaqueValue1,vendorname2=opaqueValue2

Rust Tracing

docs.rs/tracing

Events

use tracing::{event, info, Level};

// records an event outside of any span context:
event!(Level::INFO, "something happened");

info!(foo=blah, "something else happened")

info!(target:"otel::tracing", "Only exported to tracing")

Spans

use tracing::{span, Level};

let span = span!(Level::info, "my span");
// Enter the span, returning a guard object.
let _enter = span.enter();

let json = info_span!("json.parse").in_scope(||
    serde_json::from_slice(&buf)
)?;
// Any trace events that occur before the guard is
// dropped will occur within the span.

// Dropping the guard will exit the span.

Automatic Instrumentation

#[tracing::instrument]
pub fn my_function(my_arg: usize) {
    // This event will be recorded inside a span named `my_function`
    // with the field `my_arg`.
    info!("inside my_function!");
}