Struct TracingContext

pub struct TracingContext(Context);

Context for tracing used for propagating tracing information in a distributed system.

Generally, the caller of a service should create a tracing context from the current tracing span and pass it to the callee through the network. The callee will then attach its local tracing span as a child of the tracing context, so that the external tracing service can associate them in a single trace.

The tracing context must be serialized and deserialized when passing through the network. There’re two ways to do this:

• For RPC calls with clear caller/callee relationship, the tracing context can be serialized into the W3C trace context format and passed in HTTP headers seamlessly with a service middleware. For example, the DDL requests from the frontend to the meta service.
• For RPC calls with no clear caller/callee relationship or with asynchronous semantics, the tracing context should be passed manually as a protobuf field in the request and response for better lifetime management. For example, the exchange services between streaming actors or batch stages, and the create_task requests from the frontend to the batch service.

See Trace Context for more information.

Tuple Fields

0: Context

Implementations

impl TracingContext

pub fn from_span(span: &Span) -> Self

Create a new tracing context from a tracing span.

pub fn from_current_span() -> Self

Create a new tracing context from the current tracing span considered by the subscriber.

pub fn none() -> Self

Create a no-op tracing context.

pub fn attach(&self, span: Span) -> Span

Attach the given span as a child of the context. Returns the attached span.

fn to_w3c(&self) -> HashMap<String, String>

Convert the tracing context to the W3C trace context format.

fn from_w3c(fields: &HashMap<String, String>) -> Self

Create a new tracing context from the W3C trace context format.

pub fn to_protobuf(&self) -> HashMap<String, String>

Convert the tracing context to the protobuf format.

pub fn from_protobuf(fields: &HashMap<String, String>) -> Self

Create a new tracing context from the protobuf format.

pub fn to_http_headers(&self) -> HeaderMap

Convert the tracing context to the W3C trace context format in HTTP headers.

pub fn from_http_headers(headers: &HeaderMap) -> Option<Self>

Create a new tracing context from the W3C trace context format in HTTP headers.

Returns None if the headers are invalid.

Trait Implementations

impl Clone for TracingContext

fn clone(&self) -> TracingContext

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for TracingContext

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.