std/trace

Index

• type Span
• type Ring
  • method Ring.middleware
  • method Ring.record
  • method Ring.spans
  • method Ring.handler
• fn ring
• fn id

Types

Span

struct Span {
  id: Str
  name: Str
  start_ms: Int
  micros: Int
  status: Int
} derive Json

One timed piece of work of a request: the request’s id, the span’s name (request for the whole request, a program’s own for the rest), when it started (Unix milliseconds), how long it took (microseconds), and the response status for request spans (0 otherwise).

Source: std/trace.xo:12

Ring

struct Ring {
  buf: Mutex[List[Span]]
  cap: Int
}

A bounded ring of the last cap spans. Cloning shares it. Its fields are internal.

Source: std/trace.xo:22

Ring.middleware

fn (r: Ring) middleware(rand: Rand, clock: Clock) -> fn(http.Request, http.Next) -> http.Response uses (rand, clock)

The request id middleware (router.wrap(ring.middleware(rand, clock))): takes the id from the X-Request-Id header (when it is 1 to 64 printable characters) or makes a random 64 bit one, puts it in the request (id(req)), answers it in the X-Request-Id header, and records a request span.

Source: std/trace.xo:35

Ring.record

fn (r: Ring) record(id: Str, name: Str, start: Time, d: Duration)

Records a span of the work started at start that took d, for the request id.

Source: std/trace.xo:42

Ring.spans

fn (r: Ring) spans(min: Duration, n: Int) -> List[Span]

The spans, newest first, of at most n (all when n <= 0) whose duration is at least min.

Source: std/trace.xo:46

Ring.handler

fn (r: Ring) handler(auth: fn(http.Request) -> Bool) -> fn(http.Request) -> http.Response

A handler answering the spans as JSON (?slow=MILLIS&n=N; defaults 0 and 100): router.handle("GET /debug/requests", ring.handler(auth)); a request for which auth answers false gets 403.

Source: std/trace.xo:51

Functions

ring

fn ring(cap: Int = 1000) -> Ring

A ring of the last cap spans (default 1000).

Source: std/trace.xo:28

id

fn id(req: http.Request) -> Str

The id of a request that passed through the middleware, else “”.

Source: std/trace.xo:38