Hide the tracing implications of spawning tasks or threads

Summary:
As we are migrating from slog to tracing, we will need to do the same thing everywhere we spawn a tokio task or a thread: propagate the parent span.
This will allow us to behave conceptually closer to the slog way of thinking.

To make it easy to transition, introduce:
* `mononoke::spawn_task` that will replace `tokio::spawn`
* `mononoke::spawn_thread` that will replace `thread::spawn`
Both will silently do whatever they need to do for `tracing` to be seemlessly functional.

Reviewed By: markbt

Differential Revision: D68956886

fbshipit-source-id: a28bd0d90ab5dcde04ea03f78a9aab1940566e7f

eden/mononoke/mononoke_macros/Cargo.toml

@@ -10,3 +10,5 @@ license = "GPLv2+"
 [dependencies]
 justknobs = { version = "0.1.0", git = "https://github.com/facebookexperimental/rust-shed.git", branch = "main" }
 mononoke_proc_macros = { version = "0.1.0", path = "proc_macros" }
+tokio = { version = "1.41.0", features = ["full", "test-util", "tracing"] }
+tracing = { version = "0.1.41", features = ["attributes", "valuable"] }

eden/mononoke/mononoke_macros/src/lib.rs

@@ -6,15 +6,41 @@
  */
 
 pub mod mononoke {
+    use std::future::Future;
+    use std::thread;
+
     use justknobs::test_helpers;
     use justknobs::test_helpers::JustKnobsInMemory;
     pub use mononoke_proc_macros::fbinit_test;
     pub use mononoke_proc_macros::test;
+    use tokio::task;
+    use tracing::Instrument;
+    use tracing::Span;
 
     pub fn override_just_knobs() {
         let just_knobs_json = include_str!("../just_knobs_defaults/just_knobs.json");
         test_helpers::override_just_knobs(
             JustKnobsInMemory::from_json(just_knobs_json).expect("failed to parse just knobs json"),
         );
     }
+
+    pub fn spawn_task<F>(future: F) -> task::JoinHandle<F::Output>
+    where
+        F: Future + Send + 'static,
+        F::Output: Send + 'static,
+    {
+        task::spawn(future.in_current_span())
+    }
+
+    pub fn spawn_thread<F, Output>(func: F) -> thread::JoinHandle<Output>
+    where
+        F: FnOnce() -> Output + Send + 'static,
+        Output: Send + 'static,
+    {
+        let current_span = Span::current();
+        thread::spawn(move || {
+            let _ = current_span.enter();
+            func()
+        })
+    }
 }