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use crate::{trace::SpanContext, KeyValue};
use std::borrow::Cow;
use std::error::Error;
use std::time::SystemTime;
/// The interface for a single operation within a trace.
///
/// Spans can be nested to form a trace tree. Each trace contains a root span,
/// which typically describes the entire operation and, optionally, one or more
/// sub-spans for its sub-operations.
///
/// The span `name` concisely identifies the work represented by the span, for
/// example, an RPC method name, a function name, or the name of a subtask or
/// stage within a larger computation. The span name should be the most general
/// string that identifies a (statistically) interesting class of spans, rather
/// than individual span instances while still being human-readable. That is,
/// `"get_user"` is a reasonable name, while `"get_user/314159"`, where `"314159"` is
/// a user ID, is not a good name due to its high cardinality. _Generality_
/// should be prioritized over _human-readability_.
///
/// For example, here are potential span names for an endpoint that gets a
/// hypothetical account information:
///
/// | Span Name | Guidance |
/// | ----------------- | ------------ |
/// | `get` | Too general |
/// | `get_account/42` | Too specific |
/// | `get_account` | Good, and account_id=42 would make a nice Span attribute |
/// | `get_account/{accountId}` | Also good (using the "HTTP route") |
///
/// The span's start and end timestamps reflect the elapsed real time of the
/// operation.
///
/// For example, if a span represents a request-response cycle (e.g. HTTP or an
/// RPC), the span should have a start time that corresponds to the start time
/// of the first sub-operation, and an end time of when the final sub-operation
/// is complete. This includes:
///
/// * receiving the data from the request
/// * parsing of the data (e.g. from a binary or json format)
/// * any middleware or additional processing logic
/// * business logic
/// * construction of the response
/// * sending of the response
///
/// Child spans (or in some cases events) may be created to represent
/// sub-operations which require more detailed observability. Child spans should
/// measure the timing of the respective sub-operation, and may add additional
/// attributes.
pub trait Span {
/// Record an event in the context this span.
///
/// Note that the OpenTelemetry project documents certain "[standard
/// attributes]" that have prescribed semantic meanings and are available via
/// the [opentelemetry_semantic_conventions] crate.
///
/// [standard attributes]: https://github.com/open-telemetry/opentelemetry-specification/blob/v1.9.0/specification/trace/semantic_conventions/README.md
/// [opentelemetry_semantic_conventions]: https://docs.rs/opentelemetry-semantic-conventions
fn add_event<T>(&mut self, name: T, attributes: Vec<KeyValue>)
where
T: Into<Cow<'static, str>>,
{
self.add_event_with_timestamp(name, crate::time::now(), attributes)
}
/// Record an error as an event for this span.
///
/// An additional call to [Span::set_status] is required if the status of the
/// span should be set to error, as this method does not change the span status.
///
/// If this span is not being recorded then this method does nothing.
fn record_error(&mut self, err: &dyn Error) {
if self.is_recording() {
let attributes = vec![KeyValue::new("exception.message", err.to_string())];
self.add_event("exception", attributes);
}
}
/// Record an event with a timestamp in the context this span.
///
/// Note that the OpenTelemetry project documents certain "[standard
/// attributes]" that have prescribed semantic meanings and are available via
/// the [opentelemetry_semantic_conventions] crate.
///
/// [standard attributes]: https://github.com/open-telemetry/opentelemetry-specification/blob/v1.9.0/specification/trace/semantic_conventions/README.md
/// [opentelemetry_semantic_conventions]: https://docs.rs/opentelemetry-semantic-conventions
fn add_event_with_timestamp<T>(
&mut self,
name: T,
timestamp: SystemTime,
attributes: Vec<KeyValue>,
) where
T: Into<Cow<'static, str>>;
/// A reference to the [`SpanContext`] for this span.
fn span_context(&self) -> &SpanContext;
/// Returns `true` if this span is recording information.
///
/// Spans will not be recording information after they have ended.
///
/// This flag may be `true` despite the entire trace being sampled out. This
/// allows recording and processing of information about the individual
/// spans without sending it to the backend. An example of this scenario may
/// be recording and processing of all incoming requests for the processing
/// and building of SLA/SLO latency charts while sending only a subset -
/// sampled spans - to the backend.
fn is_recording(&self) -> bool;
/// Set an attribute of this span.
///
/// Setting an attribute with the same key as an existing attribute
/// results in both being stored as attribute, without any de-duplication
/// performed.
///
/// Note that the OpenTelemetry project documents certain "[standard
/// attributes]" that have prescribed semantic meanings and are available via
/// the [opentelemetry_semantic_conventions] crate.
///
/// [standard attributes]: https://github.com/open-telemetry/opentelemetry-specification/blob/v1.9.0/specification/trace/semantic_conventions/README.md
/// [opentelemetry_semantic_conventions]: https://docs.rs/opentelemetry-semantic-conventions
fn set_attribute(&mut self, attribute: KeyValue);
/// Set multiple attributes of this span.
///
/// Setting an attribute with the same key as an existing attribute
/// results in both being stored as attribute, without any de-duplication
/// performed.
///
/// Note that the OpenTelemetry project documents certain "[standard
/// attributes]" that have prescribed semantic meanings and are available via
/// the [opentelemetry_semantic_conventions] crate.
///
/// [standard attributes]: https://github.com/open-telemetry/opentelemetry-specification/blob/v1.9.0/specification/trace/semantic_conventions/README.md
/// [opentelemetry_semantic_conventions]: https://docs.rs/opentelemetry-semantic-conventions
fn set_attributes(&mut self, attributes: impl IntoIterator<Item = KeyValue>) {
if self.is_recording() {
for attr in attributes.into_iter() {
self.set_attribute(attr);
}
}
}
/// Sets the status of this `Span`.
///
/// If used, this will override the default span status, which is [`Status::Unset`].
fn set_status(&mut self, status: Status);
/// Updates the span's name.
///
/// After this update, any sampling behavior based on the name will depend on
/// the implementation.
fn update_name<T>(&mut self, new_name: T)
where
T: Into<Cow<'static, str>>;
/// Adds [`Link`] to another [`SpanContext`].
///
/// This method allows linking the current span to another span, identified by its `SpanContext`. Links can be used
/// to connect spans from different traces or within the same trace. Attributes can be attached to the link to
/// provide additional context or metadata.
///
/// # Arguments
///
/// * `span_context` - The `SpanContext` of the span to link to. This represents the target span's unique identifiers
/// and trace information.
/// * `attributes` - A vector of `KeyValue` pairs that describe additional attributes of the link. These attributes
/// can include any contextual information relevant to the link between the spans.
///
/// [`Link`]: crate::trace::Link
fn add_link(&mut self, span_context: SpanContext, attributes: Vec<KeyValue>);
/// Signals that the operation described by this span has now ended.
fn end(&mut self) {
self.end_with_timestamp(crate::time::now());
}
/// Signals that the operation described by this span ended at the given time.
fn end_with_timestamp(&mut self, timestamp: SystemTime);
}
/// `SpanKind` describes the relationship between the [`Span`], its parents, and
/// its children in a trace.
///
/// `SpanKind` describes two independent properties that benefit tracing systems
/// during analysis:
///
/// The first property described by `SpanKind` reflects whether the span is a
/// "logical" remote child or parent. By "logical", we mean that the span is
/// logically a remote child or parent, from the point of view of the library
/// that is being instrumented. Spans with a remote parent are interesting
/// because they are sources of external load. Spans with a remote child are
/// interesting because they reflect a non-local system dependency.
///
/// The second property described by `SpanKind` reflects whether a child span
/// represents a synchronous call. When a child span is synchronous, the parent
/// is expected to wait for it to complete under ordinary circumstances. It can
/// be useful for tracing systems to know this property, since synchronous spans
/// may contribute to the overall trace latency. Asynchronous scenarios can be
/// remote or local.
///
/// In order for `SpanKind` to be meaningful, callers should arrange that a
/// single span does not serve more than one purpose. For example, a server-side
/// span should not be used directly as the parent of another remote span. As a
/// simple guideline, instrumentation should create a new span prior to
/// extracting and serializing the SpanContext for a remote call.
///
/// Note: there are complex scenarios where a `SpanKind::Client` span may have a
/// child that is also logically a `SpanKind::Client` span, or a
/// `SpanKind::Producer` span might have a local child that is a
/// `SpanKind::Client` span, depending on how the various libraries that are
/// providing the functionality are built and instrumented. These scenarios,
/// when they occur, should be detailed in the semantic conventions appropriate
/// to the relevant libraries.
///
/// To summarize the interpretation of these kinds:
///
/// | `SpanKind` | Synchronous | Asynchronous | Remote Incoming | Remote Outgoing |
/// |---|---|---|---|---|
/// | `Client` | yes | | | yes |
/// | `Server` | yes | | yes | |
/// | `Producer` | | yes | | maybe |
/// | `Consumer` | | yes | maybe | |
/// | `Internal` | | | | |
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum SpanKind {
/// Indicates that the span describes a request to some remote service. This
/// span is usually the parent of a remote `SpanKind::Server` span and does
/// not end until the response is received.
Client,
/// Indicates that the span covers server-side handling of a synchronous RPC
/// or other remote request. This span is often the child of a remote
/// `SpanKind::Client` span that was expected to wait for a response.
Server,
/// Indicates that the span describes the initiators of an asynchronous
/// request. This parent span will often end before the corresponding child
/// `SpanKind::Consumer` span, possibly even before the child span starts.
///
/// In messaging scenarios with batching, tracing individual messages
/// requires a new `SpanKind::Producer` span per message to be created.
Producer,
/// Indicates that the span describes a child of an asynchronous
/// `SpanKind::Producer` request.
Consumer,
/// Default value.
///
/// Indicates that the span represents an internal operation within an
/// application, as opposed to an operations with remote parents or
/// children.
Internal,
}
/// The status of a [`Span`].
///
/// These values form a total order: Ok > Error > Unset. This means that setting
/// `Status::Ok` will override any prior or future attempts to set a status with
/// `Status::Error` or `Status::Unset`.
///
/// The status should remain unset, except for the following circumstances:
///
/// Generally, instrumentation libraries should not set the code to
/// `Status::Ok`, unless explicitly configured to do so. Instrumentation
/// libraries should leave the status code as unset unless there is an error.
///
/// Application developers and operators may set the status code to
/// `Status::Ok`.
///
/// When span status is set to `Status::Ok` it should be considered final and
/// any further attempts to change it should be ignored.
///
/// Analysis tools should respond to a `Status::Ok` status by suppressing any
/// errors they would otherwise generate. For example, to suppress noisy errors
/// such as 404s.
///
/// Only the value of the last call will be recorded, and implementations are
/// free to ignore previous calls.
#[derive(Default, Debug, Clone, PartialEq, Eq, PartialOrd)]
pub enum Status {
/// The default status.
#[default]
Unset,
/// The operation contains an error.
Error {
/// The description of the error
description: Cow<'static, str>,
},
/// The operation has been validated by an application developer or operator to
/// have completed successfully.
Ok,
}
impl Status {
/// Create a new error status with a given description.
///
/// # Examples
///
/// ```
/// use opentelemetry::trace::Status;
///
/// // record error with `str` description
/// let error_status = Status::error("something went wrong");
///
/// // or with `String` description
/// let error_status = Status::error(format!("too many foos: {}", 42));
/// # drop(error_status);
/// ```
pub fn error(description: impl Into<Cow<'static, str>>) -> Self {
Status::Error {
description: description.into(),
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn status_order() {
assert!(Status::Ok > Status::error(""));
assert!(Status::error("") > Status::Unset);
}
}