simon/ocaml-trace
1
0
Fork 0
mirror of https://github.com/ocaml-tracing/ocaml-trace.git synced 2026-05-06 09:25:28 -04:00
Code Issues Projects Releases Packages Wiki Activity Actions

trace.lwt: do not provide a ambient-span-provider except in docs; add docs

Browse source 
it's too backend-specific, it would clash eg with the opentelemetry
ambient span provider. Better let the user know this.
This commit is contained in:
Simon Cruanes 2026-04-15 10:55:55 -04:00
parent 42bf837113
commit 5629555a72
1 changed files with 30 additions and 10 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

40
src/lwt/trace_lwt.ml
View file

@ -1,21 +1,41 @@
(** Optional interface with lwt.
This provides a Lwt-friendly variant of {!Trace_core.with_span}.
To track the ambient span, which can be useful for some backends or for
async spans, you can use [Ambient_context_lwt], a collector-specific ambient
span provider (eg [Opentelemetry_trace] comes with one), or define your own
like this:
{[
(* new key to track the current span in lwt context *)
let k_ambient_span : span Lwt.key = Lwt.new_key ()
(* ambient span provider, install it using Trace_core.set_ambient_context_provider] *)
let ambient_span_provider : Trace_core.Ambient_span_provider.t =
ASP_some
( (),
{
get_current_span = (fun () -> Lwt.get k_ambient_span);
with_current_span_set_to =
(fun () span f ->
Lwt.with_value k_ambient_span (Some span) (fun () -> f span));
} )
]}
@since NEXT_RELEASE *)
open Trace_core
let k_ambient_span : span Lwt.key = Lwt.new_key ()
(** [with_span name f] enters a span [sp], calls [f sp] which returns a Lwt
promise, and make sure to exit the span [sp] when [f sp] exits (or fails).
let ambient_span_provider : Trace_core.Ambient_span_provider.t =
ASP_some
( (),
{
get_current_span = (fun () -> Lwt.get k_ambient_span);
with_current_span_set_to =
(fun () span f ->
Lwt.with_value k_ambient_span (Some span) (fun () -> f span));
} )
This is similar to {!Trace_core.with_span} but it respects the promise
semnatics of Lwt (ie. it doesn't exit the span immediately instead of
waiting for the promise to end).
To track the current span you still need to install a Lwt-friendly
{!Trace_core.Ambient_span_provider.t} (probably using {!Lwt.with_value}). *)
let with_span ?level ?__FUNCTION__ ~__FILE__ ~__LINE__ ?parent ?params ?data
name (f : span -> 'a Lwt.t) : 'a Lwt.t =
if Trace_core.enabled () then (