node: avoid automatic microtask runs

Since we are taking control of the microtask queue it makes sense to
disable autorun and only run microtasks when necessary. Just setting
isolate->SetAutorunMicrotasks(false) would cause _tickCallback() not to
be called.

Automatically running the microtask queue will cause it to run:

* After callback invocation
* Inside _tickCallback()
* After _tickCallback() invocation

The third one is unnecessary as the microtask queue is guaranteed to be
empty at this point. The first only needs to be run manually when
_tickCallback() isn't going to be called by MakeCallback().

Reviewed-by: Trevor Norris <trev.norris@gmail.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/async-wrap-inl.h b/src/async-wrap-inl.h
index 324c57b9ae..59157cc0f4 100644
--- a/src/async-wrap-inl.h
+++ b/src/async-wrap-inl.h
@@ -139,6 +139,10 @@ inline v8::Handle<v8::Value> AsyncWrap::MakeDomainCallback(
   }
 
   if (tick_info->length() == 0) {
+    env()->isolate()->RunMicrotasks();
+  }
+
+  if (tick_info->length() == 0) {
     tick_info->set_index(0);
     return ret;
   }
@@ -202,6 +206,10 @@ inline v8::Handle<v8::Value> AsyncWrap::MakeCallback(
   }
 
   if (tick_info->length() == 0) {
+    env()->isolate()->RunMicrotasks();
+  }
+
+  if (tick_info->length() == 0) {
     tick_info->set_index(0);
     return ret;
   }