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(doc new) Improve docs for Opentelemetry_lwt

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Elliott Cable 2023-06-14 00:27:25 +00:00
parent dcf13581e5
commit c5d0bbcb03
2 changed files with 31 additions and 2 deletions
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14
src/lwt/opentelemetry_lwt.ml
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@ -11,6 +11,10 @@ module GC_metrics = GC_metrics
module Metrics_callbacks = Metrics_callbacks
module Trace_context = Trace_context
(** See {!Opentelemetry.Scope}; but with several functions overridden to use
[Lwt.Sequence_associated_storage] instead of our homegrown {!Thread_local}.
@see <https://github.com/ocsigen/lwt/blob/5.4.1/src/core/lwt.ml#L739-L775> Lwt.Sequence_associated_storage *)
module Scope = struct
include Scope
@ -20,6 +24,10 @@ module Scope = struct
(**/**)
(** Obtain current scope from Lwt's sequence-associated storage, if one
exists; see {!with_scope}.
@see <https://ocaml.org/p/lwt/5.5.0/doc/Lwt/index.html#val-get> Lwt.get *)
let get_surrounding ?scope () : t option =
let surrounding = Lwt.get _global_scope_key in
match scope, surrounding with
@ -27,6 +35,12 @@ module Scope = struct
| None, Some _ -> surrounding
| None, None -> None
(** [with_scope sc f] calls [f()] in a context where [sc] is the
sequence-local implicit {!Scope.t}; then reverts to the previous local
scope, if any. Lwt will suspend and restore this implicit scope as tasks
are suspended and restored.
@see <https://ocaml.org/p/lwt/5.5.0/doc/Lwt/index.html#val-with_value> Lwt.with_value *)
let[@inline] with_scope (sc : t) (f : unit -> 'a) : 'a =
Lwt.with_value _global_scope_key (Some sc) f
end

19
src/opentelemetry.ml
View file

@ -530,14 +530,24 @@ module Scope = struct
(**/**)
(** Obtain current scope from thread-local storage, if available *)
(** Obtain current scope from thread-local storage, if available.
{b NOTE} In an Lwt context, make sure to use
{!Opentelemetry_lwt.Scope.get_surrounding} instead, as thread-local
storage will probably not interact with suspension/resumption of green
threads as expected. *)
let get_surrounding ?scope () : t option =
match scope with
| Some _ -> scope
| None -> Thread_local.get _global_scope
(** [with_scope sc f] calls [f()] in a context where [sc] is the
(thread)-local scope, then reverts to the previous local scope, if any. *)
(thread)-local scope, then reverts to the previous local scope, if any.
{b NOTE} In an Lwt context, make sure to use
{!Opentelemetry_lwt.Scope.with_scope} instead, as thread-local storage
will probably not interact with suspension/resumption of green threads as
expected. *)
let[@inline] with_scope (sc : t) (f : unit -> 'a) : 'a =
Thread_local.with_ _global_scope sc (fun _ -> f ())
end
@ -728,6 +738,11 @@ module Trace = struct
surrounding context, or [scope], or [trace_id], but will always
create a fresh new trace ID.
{b NOTE} In an Lwt context, make sure to use
{!Opentelemetry_lwt.Trace.with_} instead, as thread-local storage will
probably not interact with suspension/resumption of green threads as
expected.
{b NOTE} be careful not to call this inside a Gc alarm, as it can
cause deadlocks. *)
let with_ ?(force_new_trace_id = false) ?trace_state ?service_name