feat(common): add current thread id API (#1569)

morrisonlevi · gyuheon0h · web-flow · commit 367c8b24f8c4 · 2026-02-17T20:25:57.000Z
# What does this PR do? Adds a new public helper API, `libdd_common::threading::get_current_thread_id() -> i64`, with platform-specific implementations for Linux, macOS, and Windows. It updates `libdd-profiling`'s `add_samples` benchmark to always include a numeric `"thread id"` label in both `try_add_sample` and `try_add_sample2` paths. # Motivation This PR improves the `add_samples` benchmark because in the future I want to modify the internals of our implementation, and I want labels to be represented in the benchmark. @gyuheon0h asked for it to be in common so it could be used in other places as well. This is fine with me, as long as we keep the i64 representation for profiling. # Additional Notes Supported implementations: - Linux: `syscall(SYS_gettid)`, since `gettid()` does not exist on older glibc versions. - macOS: `pthread_threadid_np` - Windows: `GetCurrentThreadId` via `windows-sys` Unsupported platforms fail at compile time via `compile_error!`. # How to test the change? 1. Check out branch `pr1/add-samples-benchmark`. 2. Run compile checks: - `cargo check -p libdd-common` - `cargo check -p libdd-profiling` - `cargo check -p libdd-profiling --benches` 3. Run benchmark: - `cargo bench -p libdd-profiling --bench main -- add_sample --noplot` 4. Confirm: - benchmark runs successfully - `add_samples` includes `"thread id"` labels for both legacy and api2 benchmark loops Co-authored-by: gyuheon.oh <gyuheon.oh@datadoghq.com>
diff --git a/libdd-common/Cargo.toml b/libdd-common/Cargo.toml
@@ -47,7 +47,7 @@ const_format = "0.2.34"
 nix = { version = "0.29", features = ["process"] }
 [target.'cfg(windows)'.dependencies.windows-sys]
 version = "0.52"
-features = ["Win32_Foundation", "Win32_System_Performance"]
+features = ["Win32_Foundation", "Win32_System_Performance", "Win32_System_Threading"]
 
 [target.'cfg(unix)'.dependencies]
 rustls = { version = "0.23", default-features = false, optional = true, features = ["aws-lc-rs"] }
diff --git a/libdd-common/src/lib.rs b/libdd-common/src/lib.rs
@@ -28,6 +28,7 @@ pub mod rate_limiter;
 pub mod tag;
 #[cfg(any(test, feature = "test-utils"))]
 pub mod test_utils;
+pub mod threading;
 pub mod timeout;
 pub mod unix_utils;
 pub mod worker;
diff --git a/libdd-common/src/threading.rs b/libdd-common/src/threading.rs
@@ -0,0 +1,36 @@
+// Copyright 2026-Present Datadog, Inc. https://www.datadoghq.com/
+// SPDX-License-Identifier: Apache-2.0
+
+/// Returns a numeric identifier for the current OS thread.
+#[cfg(target_os = "linux")]
+pub fn get_current_thread_id() -> i64 {
+    // SAFETY: syscall(SYS_gettid) has no preconditions for current thread.
+    unsafe { libc::syscall(libc::SYS_gettid) as i64 }
+}
+
+/// Returns a numeric identifier for the current OS thread.
+#[cfg(target_os = "macos")]
+pub fn get_current_thread_id() -> i64 {
+    let mut tid: u64 = 0;
+    // SAFETY: `pthread_threadid_np` has no preconditions for current thread
+    // when pthread_t is 0 and output pointer is valid.
+    let rc = unsafe { libc::pthread_threadid_np(0, &mut tid) };
+    debug_assert_eq!(
+        rc,
+        0,
+        "pthread_threadid_np failed: {rc} ({})",
+        std::io::Error::from_raw_os_error(rc)
+    );
+    tid as i64
+}
+
+/// Returns a numeric identifier for the current OS thread.
+#[cfg(target_os = "windows")]
+pub fn get_current_thread_id() -> i64 {
+    // SAFETY: GetCurrentThreadId has no preconditions.
+    unsafe { windows_sys::Win32::System::Threading::GetCurrentThreadId() as i64 }
+}
+
+/// Returns a numeric identifier for the current OS thread.
+#[cfg(not(any(target_os = "linux", target_os = "macos", target_os = "windows")))]
+compile_error!("libdd_common::threading::get_current_thread_id is unsupported on this platform");
diff --git a/libdd-profiling/benches/add_samples.rs b/libdd-profiling/benches/add_samples.rs
@@ -2,8 +2,9 @@
 // SPDX-License-Identifier: Apache-2.0
 
 use criterion::*;
+use libdd_common::threading::get_current_thread_id;
 use libdd_profiling::api2::Location2;
-use libdd_profiling::profiles::datatypes::{Function, FunctionId2, MappingId2};
+use libdd_profiling::profiles::datatypes::{Function, FunctionId2, MappingId2, StringId2};
 use libdd_profiling::{self as profiling, api, api2};
 
 fn make_sample_types() -> Vec<api::SampleType> {
@@ -103,6 +104,14 @@ pub fn bench_add_sample_vs_add2(c: &mut Criterion) {
 
     let strings = dict.strings();
     let functions = dict.functions();
+    let thread_id = get_current_thread_id();
+    let thread_id_key: StringId2 = strings.try_insert("thread id").unwrap().into();
+    let labels_api = vec![api::Label {
+        key: "thread id",
+        str: "",
+        num: thread_id,
+        num_unit: "",
+    }];
 
     let frames2 = frames.map(|f| {
         let set_id = functions
@@ -127,7 +136,7 @@ pub fn bench_add_sample_vs_add2(c: &mut Criterion) {
                 let sample = api::Sample {
                     locations: locations.clone(),
                     values: &values,
-                    labels: vec![],
+                    labels: labels_api.clone(),
                 };
                 black_box(profile.try_add_sample(sample, None)).unwrap();
             }
@@ -145,8 +154,7 @@ pub fn bench_add_sample_vs_add2(c: &mut Criterion) {
             .unwrap();
             let (locations, values) = make_stack_api2(frames2.as_slice());
             for _ in 0..1000 {
-                // Provide an empty iterator for labels conversion path
-                let labels_iter = std::iter::empty::<anyhow::Result<api2::Label>>();
+                let labels_iter = [Ok(api2::Label::num(thread_id_key, thread_id, ""))].into_iter();
                 // SAFETY: all ids come from the profile's dictionary.
                 black_box(unsafe {
                     profile.try_add_sample2(&locations, &values, labels_iter, None)
