nsolid: add start/stopTrackingHeapObjects APIs

This patch implements triggers for `startTrackingHeapObjects`
and `stopTrackingHeapObjects` in the heap profiler.

The implementation is based on what the inspector does:

The `startTrackingHeapObjects` will simply activate that in the
HeapProfiler and; the `stopTrackingHeapObjects` will create a heap
snapshot and deactivate the `TrackingHeapObjects` in the Heap
profiler.

This patch also includes the `trackAllocations` option supported.

PR-URL: #48
Signed-off-by: Juan José Arboleda <soyjuanarbol@gmail.com>
Co-authored-by: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-by: Trevor Norris <trev.norris@gmail.com>
Reviewed-by: Santiago Gimeno <santiago.gimeno@gmail.com>

src/nsolid.cc

@@ -508,6 +508,22 @@ int CpuProfiler::get_cpu_profile_(SharedEnvInst envinst,
                                                    deleter);
 }
 
+int Snapshot::start_tracking_heap_objects_(SharedEnvInst envinst,
+                                           bool redacted,
+                                           bool trackAllocations,
+                                           uint64_t duration,
+                                           internal::user_data data,
+                                           snapshot_proxy_sig proxy) {
+  return NSolidHeapSnapshot::Inst()->StartTrackingHeapObjects(
+      envinst, redacted, trackAllocations, duration, std::move(data), proxy);
+}
+
+int Snapshot::StopTrackingHeapObjects(SharedEnvInst envinst) {
+  if (envinst == nullptr)
+    return UV_ESRCH;
+
+  return NSolidHeapSnapshot::Inst()->StopTrackingHeapObjects(envinst);
+}
 
 int Snapshot::get_snapshot_(SharedEnvInst envinst,
                             bool redacted,

src/nsolid.h

@@ -954,6 +954,7 @@ class NODE_EXTERN Snapshot {
    * concurrent snapshot per thread can be taken.
    *
    * @param envinst SharedEnvInst of thread to take the snapshot from.
+   * @param redacted to get redacted strings in the heap snapshot.
    * @param cb callback function with the following signature:
    * `cb(int status, std::string snapshot, ...Data)`. It will be called from the
    * NSolid thread.
@@ -967,7 +968,50 @@ class NODE_EXTERN Snapshot {
                           Cb&& cb,
                           Data&&... data);
 
+  /**
+   * @brief activates the heap profiler tracking objects from a specific JS
+   * thread.
+   *
+   * @param envinst SharedEnvInst of thread to take the snapshot from.
+   * @param redacted to get redacted strings in the heap snapshot.
+   * @param trackAllLocations record stack traces of allocations, set this as
+   * as true will add a significant overhead.
+   * @param duration duration in milliseconds of the heap profiler after which
+   * the heap snapshot will be returned in the callback.
+   * @param data variable number of arguments to be propagated to the callback.
+   * @param cb callback function with the following signature:
+   * `cb(int status, std::string snapshot, ...Data)`. It will be called from the
+   * NSolid thread.
+   * @param data variable number of arguments to be propagated to the callback.
+   * @return NSOLID_E_SUCCESS in case of success or a different NSOLID_E_
+   * error value otherwise.
+   */
+  template <typename Cb, typename... Data>
+  static int StartTrackingHeapObjects(SharedEnvInst envinst,
+                                      bool redacted,
+                                      bool trackAllocations,
+                                      uint64_t duration,
+                                      Cb&& cb,
+                                      Data&&... data);
+
+  /**
+   * @brief same as TakeSnapshot but stops tracking heap objects in the heap
+   * profiler.
+   *
+   * @param envinst SharedEnvInst of thread to take the snapshot from.
+   * @return NSOLID_E_SUCCESS in case of success or a different NSOLID_E_
+   * error value otherwise.
+   */
+  static int StopTrackingHeapObjects(SharedEnvInst envinst);
+
  private:
+  static int start_tracking_heap_objects_(SharedEnvInst envinst,
+                                          bool redacted,
+                                          bool trackAllocations,
+                                          uint64_t duration,
+                                          internal::user_data data,
+                                          snapshot_proxy_sig proxy);
+
   static int get_snapshot_(SharedEnvInst envinst,
                            bool redacted,
                            void* data,
@@ -1133,6 +1177,36 @@ void CpuProfiler::cpu_profiler_proxy_(int status,
   (*static_cast<G*>(data))(status, json);
 }
 
+template <typename Cb, typename... Data>
+int Snapshot::StartTrackingHeapObjects(SharedEnvInst envinst,
+                                       bool redacted,
+                                       bool trackAllocations,
+                                       uint64_t duration,
+                                       Cb&& cb,
+                                       Data&&... data) {
+  if (envinst == nullptr) {
+    return UV_ESRCH;
+  }
+
+  // NOLINTNEXTLINE(build/namespaces)
+  using namespace std::placeholders;
+  using UserData = decltype(std::bind(
+      std::forward<Cb>(cb), _1, _2, std::forward<Data>(data)...));
+
+  auto user_data = internal::user_data(new (std::nothrow) UserData(
+      std::bind(std::forward<Cb>(cb), _1, _2, std::forward<Data>(data)...)),
+                        internal::delete_proxy_<UserData>);
+  if (user_data == nullptr) {
+    return UV_ENOMEM;
+  }
+
+  return start_tracking_heap_objects_(envinst,
+                                      redacted,
+                                      trackAllocations,
+                                      duration,
+                                      std::move(user_data),
+                                      snapshot_proxy_<UserData>);
+}
 
 template <typename Cb, typename... Data>
 int Snapshot::TakeSnapshot(SharedEnvInst envinst,

src/nsolid/nsolid_api.cc

@@ -1,4 +1,5 @@
 #include "nsolid_api.h"
+#include "nsolid/nsolid_heap_snapshot.h"
 #include "nsolid_bindings.h"
 #include "node_buffer.h"
 #include "nsolid_cpu_profiler.h"
@@ -966,6 +967,7 @@ void EnvList::RemoveEnv(Environment* env) {
   // End any pending CPU profiles. This has to be done before removing the
   // EnvList from env_map_ so the checks in StopProfilingSync() pass.
   NSolidCpuProfiler::Inst()->StopProfilingSync(envinst_sp);
+  NSolidHeapSnapshot::Inst()->StopTrackingHeapObjects(envinst_sp);
 
   // Remove the GC prologue and epilogue callbacks just to be safe.
   envinst_sp->env()->isolate()->RemoveGCPrologueCallback(

src/nsolid/nsolid_heap_snapshot.cc

@@ -12,6 +12,35 @@ NSolidHeapSnapshot::NSolidHeapSnapshot() {
   ASSERT_EQ(0, in_progress_heap_snapshots_.init(true));
 }
 
+int NSolidHeapSnapshot::StartTrackingHeapObjects(
+    SharedEnvInst envinst,
+    bool redacted,
+    bool trackAllocations,
+    uint64_t duration,
+    internal::user_data data,
+    Snapshot::snapshot_proxy_sig proxy) {
+  uint64_t thread_id = envinst->thread_id();
+  nsuv::ns_mutex::scoped_lock lock(&in_progress_heap_snapshots_);
+  // We can not trigger this command if there is already a snapshot in progress
+  auto it = threads_running_snapshots_.emplace(
+        thread_id,
+        HeapSnapshotStor{ redacted, true, proxy, std::move(data) });
+  if (it.second == false) {
+    return UV_EEXIST;
+  }
+  int status = RunCommand(envinst,
+                          CommandType::Interrupt,
+                          start_tracking_heapobjects,
+                          trackAllocations,
+                          duration,
+                          this);
+  if (status != 0) {
+    // Now we are tracking heap objects in this thread
+    threads_running_snapshots_.erase(it.first);
+  }
+  return status;
+}
+
 int NSolidHeapSnapshot::GetHeapSnapshot(SharedEnvInst envinst,
                                         bool redacted,
                                         void* data,
@@ -31,13 +60,147 @@ int NSolidHeapSnapshot::GetHeapSnapshot(SharedEnvInst envinst,
 
   if (status == 0) {
     threads_running_snapshots_.emplace(
-      thread_id,
-      HeapSnapshotStor{ redacted, proxy, internal::user_data(data, deleter) });
+        thread_id,
+        HeapSnapshotStor{
+            redacted, false, proxy, internal::user_data(data, deleter)});
   }
 
   return status;
 }
 
+int NSolidHeapSnapshot::StopTrackingHeapObjects(SharedEnvInst envinst) {
+  uint64_t thread_id = envinst->thread_id();
+  nsuv::ns_mutex::scoped_lock lock(&in_progress_heap_snapshots_);
+  auto it = threads_running_snapshots_.find(thread_id);
+  // Make sure there is a snapshot running
+  if (it == threads_running_snapshots_.end())
+    return UV_ENOENT;
+
+  int er = RunCommand(envinst,
+                      CommandType::Interrupt,
+                      stop_tracking_heap_objects,
+                      this);
+  return er;
+}
+
+void NSolidHeapSnapshot::stop_tracking_heap_objects(
+    SharedEnvInst envinst,
+    NSolidHeapSnapshot* snapshotter) {
+  uint64_t thread_id = envinst->thread_id();
+  nsuv::ns_mutex::scoped_lock lock(&snapshotter->in_progress_heap_snapshots_);
+  auto it = snapshotter->threads_running_snapshots_.find(thread_id);
+  if (it == snapshotter->threads_running_snapshots_.end()) {
+    // This might happen if snapshot_cb is called before RemoveEnv. Just return;
+    return;
+  }
+
+  HeapSnapshotStor& stor = it->second;
+  // If this condition is reached. This was called by EnvList::RemoveEnv.
+  // It wants to stop any pending snapshot w/ tracking heap object.
+  if (!stor.is_tracking_heapobjects_) {
+    // If no pending trackers, just do nothing
+    // There are not peding snapshots with trackers
+    return;
+  }
+
+  v8::Isolate* isolate = envinst->isolate();
+
+  v8::HeapProfiler* profiler = isolate->GetHeapProfiler();
+  ASSERT_NOT_NULL(profiler);
+
+  v8::HandleScope scope(isolate);
+
+  const v8::HeapSnapshot* snapshot = profiler->TakeHeapSnapshot();
+  if (snapshot == nullptr) {
+    stor.cb(heap_profiler::HEAP_SNAPSHOT_FAILURE,
+            std::string(),
+            stor.data.get());
+  } else {
+    std::string snapshot_str;
+    DataOutputStream<uint64_t, v8::HeapSnapshot> stream(&snapshot_str,
+                                                        snapshot,
+                                                        &thread_id);
+
+    if (stor.redacted) {
+      const v8::RedactedHeapSnapshot snapshot_redact(snapshot);
+      snapshot_redact.Serialize(&stream);
+    } else {
+      snapshot->Serialize(&stream);
+    }
+
+    ASSERT_EQ(stor.is_tracking_heapobjects_, true);
+    profiler->StopTrackingHeapObjects();
+    stor.is_tracking_heapobjects_ = false;
+
+
+    // At this point, the snapshot is fully serialized
+    stor.cb(0, snapshot_str.c_str(), stor.data.get());
+    // Tell ZMQ that the snapshot is done
+    stor.cb(0, std::string(), stor.data.get());
+
+    // Don't leak the snapshot string
+    snapshot_str.clear();
+
+    // Work around a deficiency in the API. The HeapSnapshot object is const
+    // but we cannot call HeapProfiler::DeleteAllHeapSnapshots() because that
+    // invalidates _all_ snapshots, including those created by other tools.
+    const_cast<v8::HeapSnapshot*>(snapshot)->Delete();
+  }
+  // Delete the snapshot from the map
+  snapshotter->threads_running_snapshots_.erase(it);
+}
+
+void NSolidHeapSnapshot::start_tracking_heapobjects(
+    SharedEnvInst envinst,
+    bool trackAllocations,
+    uint64_t duration,
+    NSolidHeapSnapshot* snapshotter) {
+  uint64_t thread_id = envinst->thread_id();
+
+  nsuv::ns_mutex::scoped_lock lock(&snapshotter->in_progress_heap_snapshots_);
+  auto it = snapshotter->threads_running_snapshots_.find(thread_id);
+  ASSERT(it != snapshotter->threads_running_snapshots_.end());
+
+  HeapSnapshotStor& stor = it->second;
+  ASSERT_EQ(stor.is_tracking_heapobjects_, true);
+
+  envinst->isolate()->GetHeapProfiler()->StartTrackingHeapObjects(
+      trackAllocations);
+  if (duration > 0) {
+    // Schedule a timer to take the snapshot
+    int er = QueueCallback(duration, take_snapshot_timer, envinst, snapshotter);
+
+    if (er) {
+      // In case the the thread is already gone, the cpu profile will be stopped
+      // on RemoveEnv, so do nothing here.
+    }
+  }
+}
+
+void NSolidHeapSnapshot::take_snapshot_timer(SharedEnvInst envinst,
+                                             NSolidHeapSnapshot* snapshotter) {
+  uint64_t thread_id = envinst->thread_id();
+  nsuv::ns_mutex::scoped_lock lock(&snapshotter->in_progress_heap_snapshots_);
+  auto it = snapshotter->threads_running_snapshots_.find(thread_id);
+  // The snapshot was stopped before the timer was triggered
+  if (it == snapshotter->threads_running_snapshots_.end())
+    return;
+
+  HeapSnapshotStor& stor = it->second;
+  ASSERT_EQ(stor.is_tracking_heapobjects_, true);
+
+  // Give control back to the V8 thread
+  int er = RunCommand(envinst,
+                      CommandType::Interrupt,
+                      take_snapshot,
+                      snapshotter);
+  // NO BUENO???
+  if (er) {
+    // In case the the thread is already gone, the cpu profile will be stopped
+    // on RemoveEnv, so do nothing here.
+  }
+}
+
 void NSolidHeapSnapshot::take_snapshot(SharedEnvInst envinst,
                                        NSolidHeapSnapshot* snapshotter) {
   v8::Isolate* isolate = envinst->isolate();
@@ -75,6 +238,12 @@ void NSolidHeapSnapshot::take_snapshot(SharedEnvInst envinst,
       snapshot->Serialize(&stream);
     }
 
+    // A snapshot requested via `StopTrackingHeapObjects` or timer
+    if (stor.is_tracking_heapobjects_) {
+      profiler->StopTrackingHeapObjects();
+      stor.is_tracking_heapobjects_ = false;
+    }
+
     // Work around a deficiency in the API. The HeapSnapshot object is const
     // but we cannot call HeapProfiler::DeleteAllHeapSnapshots() because that
     // invalidates _all_ snapshots, including those created by other tools.

src/nsolid/nsolid_heap_snapshot.h

@@ -21,6 +21,7 @@ class NSolidHeapSnapshot {
  public:
   struct HeapSnapshotStor {
     bool redacted;
+    bool is_tracking_heapobjects_;
     Snapshot::snapshot_proxy_sig cb;
     internal::user_data data;
   };
@@ -36,11 +37,31 @@ class NSolidHeapSnapshot {
                       Snapshot::snapshot_proxy_sig proxy,
                       internal::deleter_sig deleter);
 
+  int StartTrackingHeapObjects(SharedEnvInst envinst,
+                               bool redacted,
+                               bool trackAllocations,
+                               uint64_t duration,
+                               internal::user_data data,
+                               Snapshot::snapshot_proxy_sig proxy);
+
+  int StopTrackingHeapObjects(SharedEnvInst envinst);
+
  private:
   NSolidHeapSnapshot();
 
+  static void start_tracking_heapobjects(SharedEnvInst envinst,
+                                         bool trackAllocations,
+                                         uint64_t duration,
+                                         NSolidHeapSnapshot*);
+
+  static void stop_tracking_heap_objects(SharedEnvInst envinst_sp,
+                                         NSolidHeapSnapshot*);
+
   static void take_snapshot(SharedEnvInst envinst_sp, NSolidHeapSnapshot*);
 
+  static void take_snapshot_timer(SharedEnvInst envinst_sp,
+                                  NSolidHeapSnapshot*);
+
   static void snapshot_cb(uint64_t thread_id,
                           int status,
                           const std::string& snapshot);