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//! # Composite Propagator
//!
//! A utility over multiple `Propagator`s to group multiple Propagators from different cross-cutting
//! concerns in order to leverage them as a single entity.
//!
//! Each composite Propagator will implement a specific Propagator type, such as TextMapPropagator,
//! as different Propagator types will likely operate on different data types.
use crate::{
propagation::{text_map_propagator::FieldIter, Extractor, Injector, TextMapPropagator},
Context,
};
use std::collections::HashSet;
/// Composite propagator for [`TextMapPropagator`]s.
///
/// A propagator that chains multiple [`TextMapPropagator`] propagators together,
/// injecting or extracting by their respective HTTP header names.
///
/// Injection and extraction from this propagator will preserve the order of the
/// injectors and extractors passed in during initialization.
///
/// # Examples
///
/// ```
/// use opentelemetry::{
/// baggage::BaggageExt,
/// propagation::{TextMapPropagator, TextMapCompositePropagator},
///
/// trace::{TraceContextExt, Tracer, TracerProvider},
/// Context, KeyValue,
/// };
/// use opentelemetry_sdk::propagation::{
/// BaggagePropagator, TraceContextPropagator,
/// };
/// use opentelemetry_sdk::trace as sdktrace;
/// use std::collections::HashMap;
///
/// // First create 1 or more propagators
/// let baggage_propagator = BaggagePropagator::new();
/// let trace_context_propagator = TraceContextPropagator::new();
///
/// // Then create a composite propagator
/// let composite_propagator = TextMapCompositePropagator::new(vec![
/// Box::new(baggage_propagator),
/// Box::new(trace_context_propagator),
/// ]);
///
/// // Then for a given implementation of `Injector`
/// let mut injector = HashMap::new();
///
/// // And a given span
/// let example_span = sdktrace::TracerProvider::default()
/// .tracer("example-component")
/// .start("span-name");
///
/// // with the current context, call inject to add the headers
/// composite_propagator.inject_context(
/// &Context::current_with_span(example_span)
/// .with_baggage(vec![KeyValue::new("test", "example")]),
/// &mut injector,
/// );
///
/// // The injector now has both `baggage` and `traceparent` headers
/// assert!(injector.get("baggage").is_some());
/// assert!(injector.get("traceparent").is_some());
/// ```
#[derive(Debug)]
pub struct TextMapCompositePropagator {
propagators: Vec<Box<dyn TextMapPropagator + Send + Sync>>,
fields: Vec<String>,
}
impl TextMapCompositePropagator {
/// Constructs a new propagator out of instances of [`TextMapPropagator`].
///
/// [`TextMapPropagator`]: TextMapPropagator
pub fn new(propagators: Vec<Box<dyn TextMapPropagator + Send + Sync>>) -> Self {
let mut fields = HashSet::new();
for propagator in &propagators {
for field in propagator.fields() {
fields.insert(field.to_string());
}
}
TextMapCompositePropagator {
propagators,
fields: fields.into_iter().collect(),
}
}
}
impl TextMapPropagator for TextMapCompositePropagator {
/// Encodes the values of the `Context` and injects them into the `Injector`.
fn inject_context(&self, context: &Context, injector: &mut dyn Injector) {
for propagator in &self.propagators {
propagator.inject_context(context, injector)
}
}
/// Retrieves encoded `Context` information using the `Extractor`. If no data was
/// retrieved OR if the retrieved data is invalid, then the current `Context` is
/// returned.
fn extract_with_context(&self, cx: &Context, extractor: &dyn Extractor) -> Context {
self.propagators
.iter()
.fold(cx.clone(), |current_cx, propagator| {
propagator.extract_with_context(¤t_cx, extractor)
})
}
fn fields(&self) -> FieldIter<'_> {
FieldIter::new(self.fields.as_slice())
}
}
#[cfg(all(test, feature = "trace"))]
mod tests {
use crate::baggage::BaggageExt;
use crate::propagation::TextMapCompositePropagator;
use crate::testing::trace::TestSpan;
use crate::{
propagation::{text_map_propagator::FieldIter, Extractor, Injector, TextMapPropagator},
trace::{SpanContext, SpanId, TraceContextExt, TraceFlags, TraceId, TraceState},
Context, KeyValue,
};
use std::collections::HashMap;
/// A test propagator that injects and extracts a single header.
#[derive(Debug)]
struct TestPropagator {
header: &'static str,
fields: Vec<String>, // used by fields method
}
impl TestPropagator {
#[allow(unreachable_pub)]
pub fn new(header: &'static str) -> Self {
TestPropagator {
header,
fields: vec![header.to_string()],
}
}
}
impl TextMapPropagator for TestPropagator {
fn inject_context(&self, cx: &Context, injector: &mut dyn Injector) {
let span = cx.span();
let span_context = span.span_context();
match self.header {
"span-id" => injector.set(self.header, format!("{:x}", span_context.span_id())),
"baggage" => injector.set(self.header, cx.baggage().to_string()),
_ => {}
}
}
fn extract_with_context(&self, cx: &Context, extractor: &dyn Extractor) -> Context {
match (self.header, extractor.get(self.header)) {
("span-id", Some(val)) => cx.with_remote_span_context(SpanContext::new(
TraceId::from_u128(1),
SpanId::from_u64(u64::from_str_radix(val, 16).unwrap()),
TraceFlags::default(),
false,
TraceState::default(),
)),
("baggage", Some(_)) => cx.with_baggage(vec![KeyValue::new("baggagekey", "value")]),
_ => cx.clone(),
}
}
fn fields(&self) -> FieldIter<'_> {
FieldIter::new(self.fields.as_slice())
}
}
fn setup() -> Context {
let mut cx = Context::default();
cx = cx.with_span(TestSpan(SpanContext::new(
TraceId::from_u128(1),
SpanId::from_u64(11),
TraceFlags::default(),
true,
TraceState::default(),
)));
// setup for baggage propagator
cx.with_baggage(vec![KeyValue::new("baggagekey", "value")])
}
fn test_data() -> Vec<(&'static str, &'static str)> {
vec![("span-id", "b"), ("baggage", "baggagekey=value")]
}
#[test]
fn zero_propogators_are_noop() {
// setup
let composite_propagator = TextMapCompositePropagator::new(vec![]);
let cx = setup();
let mut injector = HashMap::new();
composite_propagator.inject_context(&cx, &mut injector);
assert_eq!(injector.len(), 0);
for (header_name, header_value) in test_data() {
let mut extractor = HashMap::new();
extractor.insert(header_name.to_string(), header_value.to_string());
assert_eq!(
composite_propagator
.extract(&extractor)
.span()
.span_context(),
&SpanContext::empty_context()
);
}
}
#[test]
fn inject_multiple_propagators() {
let composite_propagator = TextMapCompositePropagator::new(vec![
Box::new(TestPropagator::new("span-id")),
Box::new(TestPropagator::new("baggage")),
]);
let cx = setup();
let mut injector = HashMap::new();
composite_propagator.inject_context(&cx, &mut injector);
for (header_name, header_value) in test_data() {
assert_eq!(injector.get(header_name), Some(&header_value.to_string()));
}
}
#[test]
fn extract_multiple_propagators() {
let composite_propagator = TextMapCompositePropagator::new(vec![
Box::new(TestPropagator::new("span-id")),
Box::new(TestPropagator::new("baggage")),
]);
let mut extractor = HashMap::new();
for (header_name, header_value) in test_data() {
extractor.insert(header_name.to_string(), header_value.to_string());
}
let cx = composite_propagator.extract(&extractor);
assert_eq!(
cx.span().span_context(),
&SpanContext::new(
TraceId::from_u128(1),
SpanId::from_u64(11),
TraceFlags::default(),
false,
TraceState::default(),
)
);
assert_eq!(cx.baggage().to_string(), "baggagekey=value",);
}
#[test]
fn test_get_fields() {
let test_cases = vec![
// name, header_name, expected_result
// ("single propagator", vec!["span-id"], vec!["span-id"]),
(
"multiple propagators with order",
vec!["span-id", "baggage"],
vec!["baggage", "span-id"],
),
];
for test_case in test_cases {
let test_propagators = test_case
.1
.into_iter()
.map(|name| {
Box::new(TestPropagator::new(name)) as Box<dyn TextMapPropagator + Send + Sync>
})
.collect();
let composite_propagator = TextMapCompositePropagator::new(test_propagators);
let mut fields = composite_propagator
.fields()
.map(|s| s.to_string())
.collect::<Vec<String>>();
fields.sort();
assert_eq!(fields, test_case.2);
}
}
}