Struct RequestIdLayer 

pub struct RequestIdLayer { /* private fields */ }

Middleware that ensures every request/response pair carries a stable correlation ID.

• If the incoming request already has the header (e.g. set by an upstream gateway, load balancer, or calling service), that exact value is kept and echoed back unchanged — this lets one ID follow a request across multiple services instead of getting a new one at each hop.
• Otherwise, a fresh ID is generated with generate_request_id and injected into the request before it reaches your handler, so handlers can read it like any other header.
• The same value is always set on the response, so the caller can log it too — even if it arrived with no ID and this middleware generated one.

Implementations

impl RequestIdLayer

pub fn new() -> RequestIdLayer

Uses the default header name, DEFAULT_HEADER (X-Request-Id).

pub fn header(self, name: impl Into<String>) -> RequestIdLayer

Use a different header name, e.g. "X-Correlation-Id".

Trait Implementations

impl Default for RequestIdLayer

fn default() -> RequestIdLayer

Returns the “default value” for a type.

impl Middleware for RequestIdLayer

fn accepts_streamed_body( &self, _request: &Request, _connection: &ConnectionInfo, ) -> bool

Headers only: a streamed body passes through untouched.

fn runs_inline(&self, _request: &Request, _connection: &ConnectionInfo) -> bool

In-memory only: safe on the event loop.

fn handle( &self, request: &Request, connection: &ConnectionInfo, next: &dyn Application, ) -> Result<Response, String>

fn is_passthrough( &self, _request: &Request, _connection: &ConnectionInfo, ) -> bool

true when handle would do nothing for request but call next (e.g. a rate limit that isn’t configured). A WithMiddleware stack offers the inner application’s execute_async only if every layer passes the request through. Default false.

fn answers_streamed_body( &self, _request: &Request, _connection: &ConnectionInfo, ) -> bool

true when this layer answers request itself — it doesn’t call next — and reads its body as a stream (a proxy forwarding it as it arrives). The body is then streamed whatever the layers after it and the application would say. Requires accepts_streamed_body. Since 18.3.0.

fn layer_name(&self) -> &'static str

A short name for this layer, as tools that describe an app list it (Application::middleware_names): by default the type’s name without its module path or generic parameters (CacheLayer). Since 18.28.0.