fix(profiling): adapt Stack V2 to exception-free Echion [backport 3.17] (#15052)

Backport 2c72bca from #14933 to 3.17.

## What does this PR do?

This PR updates Echion to use the latest version. 

Included Echion PRs
- [refactor: stop using exceptions for reporting
errors](P403n1x87/echion#156)
- [misc: remove Error
classes](P403n1x87/echion#164)
- [bug: avoid possibly unbounded memory
allocations](P403n1x87/echion#159)
- [fix: remove extra loop in Frame::read() for
3.13+](P403n1x87/echion#167)
- [refactor: return std::reference_wrapper over raw
pointer](P403n1x87/echion#168)

See comparison here
P403n1x87/echion@3ebeb3e...39d74a3

Co-authored-by: T. Kowalski <[email protected]>
Co-authored-by: Taegyun Kim <[email protected]>

Author: 3 people

ddtrace/internal/datadog/profiling/stack_v2/CMakeLists.txt

@@ -41,7 +41,7 @@ endif()
 
 # Add echion
 set(ECHION_COMMIT
-    "3ebeb3e975239f252fa0d6bb739344f35eaf1657" # https://github.com/kowalskithomas/echion/commit/3ebeb3e975239f252fa0d6bb739344f35eaf1657
+    "39d74a33a3f3abe810e6a29132721871e3127472" # https://github.com/P403n1x87/echion/commit/39d74a33a3f3abe810e6a29132721871e3127472
     CACHE STRING "Commit hash of echion to use")
 FetchContent_Declare(
     echion

ddtrace/internal/datadog/profiling/stack_v2/include/stack_renderer.hpp

@@ -40,7 +40,7 @@ class StackRenderer : public RendererInterface
     // the sample is created, this has to be reset.
     bool pushed_task_name = false;
 
-    void open() override {}
+    Result<void> open() override { return Result<void>::ok(); }
     void close() override {}
     void header() override {}
     void metadata(const std::string&, const std::string&) override {}

ddtrace/internal/datadog/profiling/stack_v2/src/sampler.cpp

@@ -2,6 +2,7 @@
 
 #include "thread_span_links.hpp"
 
+#include "echion/errors.h"
 #include "echion/greenlets.h"
 #include "echion/interp.h"
 #include "echion/tasks.h"
@@ -153,7 +154,7 @@ Sampler::sampling_thread(const uint64_t seq_num)
         // Perform the sample
         for_each_interp([&](InterpreterInfo& interp) -> void {
             for_each_thread(interp, [&](PyThreadState* tstate, ThreadInfo& thread) {
-                thread.sample(interp.id, tstate, wall_time_us);
+                (void)thread.sample(interp.id, tstate, wall_time_us);
             });
         });
 
@@ -245,19 +246,21 @@ Sampler::register_thread(uint64_t id, uint64_t native_id, const char* name)
     static bool has_errored = false;
     auto it = thread_info_map.find(id);
     if (it == thread_info_map.end()) {
-        try {
-            thread_info_map.emplace(id, std::make_unique<ThreadInfo>(id, native_id, name));
-        } catch (const ThreadInfo::Error& e) {
+        auto maybe_thread_info = ThreadInfo::create(id, native_id, name);
+        if (maybe_thread_info) {
+            thread_info_map.emplace(id, std::move(*maybe_thread_info));
+        } else {
             if (!has_errored) {
                 has_errored = true;
                 std::cerr << "Failed to register thread: " << std::hex << id << std::dec << " (" << native_id << ") "
                           << name << std::endl;
             }
         }
     } else {
-        try {
-            it->second = std::make_unique<ThreadInfo>(id, native_id, name);
-        } catch (const ThreadInfo::Error& e) {
+        auto maybe_thread_info = ThreadInfo::create(id, native_id, name);
+        if (maybe_thread_info) {
+            it->second = std::move(*maybe_thread_info);
+        } else {
             if (!has_errored) {
                 has_errored = true;
                 std::cerr << "Failed to register thread: " << std::hex << id << std::dec << " (" << native_id << ") "

ddtrace/internal/datadog/profiling/stack_v2/src/stack_renderer.cpp

@@ -131,15 +131,18 @@ StackRenderer::render_frame(Frame& frame)
     static constexpr std::string_view missing_name = "<unknown function>";
     std::string_view filename_str;
     std::string_view name_str;
-    try {
-        filename_str = string_table.lookup(frame.filename);
-    } catch (StringTable::Error&) {
+
+    auto maybe_filename_str = string_table.lookup(frame.filename);
+    if (maybe_filename_str) {
+        filename_str = maybe_filename_str->get();
+    } else {
         filename_str = missing_filename;
     }
 
-    try {
-        name_str = string_table.lookup(frame.name);
-    } catch (StringTable::Error&) {
+    auto maybe_name_str = string_table.lookup(frame.name);
+    if (maybe_name_str) {
+        name_str = maybe_name_str->get();
+    } else {
         name_str = missing_name;
     }
 

ddtrace/internal/datadog/profiling/stack_v2/src/stack_v2.cpp

@@ -213,16 +213,15 @@ track_greenlet(PyObject* Py_UNUSED(m), PyObject* args)
     if (!PyArg_ParseTuple(args, "lOO", &greenlet_id, &name, &frame))
         return NULL;
 
-    StringTable::Key greenlet_name;
-
-    try {
-        greenlet_name = string_table.key(name);
-    } catch (StringTable::Error&) {
+    auto maybe_greenlet_name = string_table.key(name);
+    if (!maybe_greenlet_name) {
         // We failed to get this task but we keep going
         PyErr_SetString(PyExc_RuntimeError, "Failed to get greenlet name from the string table");
         return NULL;
     }
 
+    auto greenlet_name = *maybe_greenlet_name;
+
     Py_BEGIN_ALLOW_THREADS;
     Sampler::get().track_greenlet(greenlet_id, greenlet_name, frame);
     Py_END_ALLOW_THREADS;

releasenotes/notes/profiling-echion-fix-alloc-f1204a794b1d3a1d.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    profiling: Upgrades echion to resolve an issue where stack profiler can
+    allocate a large amount of memory unnecessarily. Resolves another issue
+    where the profiler can loop infinitely on Python 3.13.
+