Trait Span

pub trait Span {
    // Required methods
    fn add_event_with_timestamp<T>(
        &mut self,
        name: T,
        timestamp: SystemTime,
        attributes: Vec<KeyValue>,
    )
       where T: Into<Cow<'static, str>>;
    fn span_context(&self) -> &SpanContext;
    fn is_recording(&self) -> bool;
    fn set_attribute(&mut self, attribute: KeyValue);
    fn set_status(&mut self, status: Status);
    fn update_name<T>(&mut self, new_name: T)
       where T: Into<Cow<'static, str>>;
    fn add_link(&mut self, span_context: SpanContext, attributes: Vec<KeyValue>);
    fn end_with_timestamp(&mut self, timestamp: SystemTime);

    // Provided methods
    fn add_event<T>(&mut self, name: T, attributes: Vec<KeyValue>)
       where T: Into<Cow<'static, str>> { ... }
    fn record_error(&mut self, err: &dyn Error) { ... }
    fn set_attributes(&mut self, attributes: impl IntoIterator<Item = KeyValue>) { ... }
    fn end(&mut self) { ... }
}

Available on crate feature trace only.

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.

Required Methods

fn add_event_with_timestamp<T>( &mut self, name: T, timestamp: SystemTime, attributes: Vec<KeyValue>, )

where T: Into<Cow<'static, str>>,

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.

fn span_context(&self) -> &SpanContext

A reference to the SpanContext for this span.

fn is_recording(&self) -> bool

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 set_attribute(&mut self, attribute: KeyValue)

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.

fn set_status(&mut self, status: Status)

Sets the status of this Span.

If used, this will override the default span status, which is Status::Unset.

fn update_name<T>(&mut self, new_name: T)

where T: Into<Cow<'static, str>>,

Updates the span’s name.

After this update, any sampling behavior based on the name will depend on the implementation.

fn add_link(&mut self, span_context: SpanContext, attributes: Vec<KeyValue>)

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.

fn end_with_timestamp(&mut self, timestamp: SystemTime)

Signals that the operation described by this span ended at the given time.

Provided Methods

fn add_event<T>(&mut self, name: T, attributes: Vec<KeyValue>)

where T: Into<Cow<'static, str>>,

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.

fn record_error(&mut self, err: &dyn Error)

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 set_attributes(&mut self, attributes: impl IntoIterator<Item = 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.

fn end(&mut self)

Signals that the operation described by this span has now ended.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl Span for BoxedSpan

impl Span for NoopSpan