From 975301d05f910a172b58aed6e330e8caf9adfd78 Mon Sep 17 00:00:00 2001
From: Levi Morrison <levi.morrison@datadoghq.com>
Date: Tue, 17 Mar 2026 20:10:26 -0600
Subject: [PATCH] feat(profiling): thread id/name as well-known strs

---
 .../src/profiles/profiles_dictionary.rs       | 12 +++++++++++
 .../collections/parallel/string_set.rs        | 14 +++++++++++++
 .../src/profiles/collections/string_set.rs    |  6 +++++-
 .../src/profiles/collections/thin_str.rs      | 20 +++++++++++++++++++
 4 files changed, 51 insertions(+), 1 deletion(-)

diff --git a/libdd-profiling-ffi/src/profiles/profiles_dictionary.rs b/libdd-profiling-ffi/src/profiles/profiles_dictionary.rs
index d3d3aa0162..24abadcb31 100644
--- a/libdd-profiling-ffi/src/profiles/profiles_dictionary.rs
+++ b/libdd-profiling-ffi/src/profiles/profiles_dictionary.rs
@@ -46,6 +46,18 @@ pub static DDOG_PROF_STRINGID2_TRACE_ENDPOINT: StringId2 =
 #[no_mangle]
 pub static DDOG_PROF_STRINGID2_SPAN_ID: StringId2 = StringId2::from(StringRef::SPAN_ID);
 
+/// A StringId that represents the string "thread id".
+/// This is always available in every string set and can be used without
+/// needing to insert it into a string set.
+#[no_mangle]
+pub static DDOG_PROF_STRINGID2_THREAD_ID: StringId2 = StringId2::from(StringRef::THREAD_ID);
+
+/// A StringId that represents the string "thread name".
+/// This is always available in every string set and can be used without
+/// needing to insert it into a string set.
+#[no_mangle]
+pub static DDOG_PROF_STRINGID2_THREAD_NAME: StringId2 = StringId2::from(StringRef::THREAD_NAME);
+
 const NULL_PROFILES_DICTIONARY: &CStr = c"passed a null pointer for a ProfilesDictionary";
 
 /// Allocates a new `ProfilesDictionary` and writes a handle to it in `handle`.
diff --git a/libdd-profiling/src/profiles/collections/parallel/string_set.rs b/libdd-profiling/src/profiles/collections/parallel/string_set.rs
index ceab5d5f17..9b1f60564a 100644
--- a/libdd-profiling/src/profiles/collections/parallel/string_set.rs
+++ b/libdd-profiling/src/profiles/collections/parallel/string_set.rs
@@ -109,6 +109,8 @@ mod tests {
             "local root span id",
             "trace endpoint",
             "span id",
+            "thread id",
+            "thread name",
         ];
         for (expected, id) in strs.iter().copied().zip(WELL_KNOWN_STRING_REFS) {
             let actual: &str = id.0.deref();
@@ -140,6 +142,12 @@ mod tests {
 
             let str = set.get(StringRef::SPAN_ID);
             assert_eq!(str, "span id");
+
+            let str = set.get(StringRef::THREAD_ID);
+            assert_eq!(str, "thread id");
+
+            let str = set.get(StringRef::THREAD_NAME);
+            assert_eq!(str, "thread name");
         };
 
         let id = set.try_insert("").unwrap();
@@ -156,6 +164,12 @@ mod tests {
 
         let id = set.try_insert("span id").unwrap();
         assert_eq!(&*id.0, &*StringRef::SPAN_ID.0);
+
+        let id = set.try_insert("thread id").unwrap();
+        assert_eq!(&*id.0, &*StringRef::THREAD_ID.0);
+
+        let id = set.try_insert("thread name").unwrap();
+        assert_eq!(&*id.0, &*StringRef::THREAD_NAME.0);
     }
 
     #[test]
diff --git a/libdd-profiling/src/profiles/collections/string_set.rs b/libdd-profiling/src/profiles/collections/string_set.rs
index 23a51b166c..f5c73ee559 100644
--- a/libdd-profiling/src/profiles/collections/string_set.rs
+++ b/libdd-profiling/src/profiles/collections/string_set.rs
@@ -58,14 +58,18 @@ impl StringRef {
     pub const LOCAL_ROOT_SPAN_ID: StringRef = StringRef(ThinStr::local_root_span_id());
     pub const TRACE_ENDPOINT: StringRef = StringRef(ThinStr::trace_endpoint());
     pub const SPAN_ID: StringRef = StringRef(ThinStr::span_id());
+    pub const THREAD_ID: StringRef = StringRef(ThinStr::thread_id());
+    pub const THREAD_NAME: StringRef = StringRef(ThinStr::thread_name());
 }
 
-pub const WELL_KNOWN_STRING_REFS: [StringRef; 5] = [
+pub const WELL_KNOWN_STRING_REFS: [StringRef; 7] = [
     StringRef::EMPTY,
     StringRef::END_TIMESTAMP_NS,
     StringRef::LOCAL_ROOT_SPAN_ID,
     StringRef::TRACE_ENDPOINT,
     StringRef::SPAN_ID,
+    StringRef::THREAD_ID,
+    StringRef::THREAD_NAME,
 ];
 
 /// Holds unique strings and provides [`StringRef`]s to fetch them later.
diff --git a/libdd-profiling/src/profiles/collections/thin_str.rs b/libdd-profiling/src/profiles/collections/thin_str.rs
index 1850ccf40a..ef646d0fc7 100644
--- a/libdd-profiling/src/profiles/collections/thin_str.rs
+++ b/libdd-profiling/src/profiles/collections/thin_str.rs
@@ -132,6 +132,24 @@ impl ThinStr<'static> {
             },
         }
     }
+
+    pub const fn thread_id() -> ThinStr<'static> {
+        ThinStr {
+            inner: ThinSlice {
+                thin_ptr: THREAD_ID.as_thin_ptr(),
+                _marker: PhantomData,
+            },
+        }
+    }
+
+    pub const fn thread_name() -> ThinStr<'static> {
+        ThinStr {
+            inner: ThinSlice {
+                thin_ptr: THREAD_NAME.as_thin_ptr(),
+                _marker: PhantomData,
+            },
+        }
+    }
 }
 
 impl Default for ThinStr<'static> {
@@ -527,6 +545,8 @@ static END_TIMESTAMP_NS: ConstString<16> = ConstString::new("end_timestamp_ns");
 static LOCAL_ROOT_SPAN_ID: ConstString<18> = ConstString::new("local root span id");
 static TRACE_ENDPOINT: ConstString<14> = ConstString::new("trace endpoint");
 static SPAN_ID: ConstString<7> = ConstString::new("span id");
+static THREAD_ID: ConstString<9> = ConstString::new("thread id");
+static THREAD_NAME: ConstString<11> = ConstString::new("thread name");
 
 #[cfg(test)]
 mod tests {