raise exception if user tries to pass large object by value (#276)

src/raylib.cc

@@ -138,6 +138,7 @@ PyObject* make_pyobjref(PyObject* worker_capsule, ObjRef objref) {
 // Error handling
 
 static PyObject *RayError;
+static PyObject *RaySizeError;
 
 // Pass arguments from Python to C++
 
@@ -574,6 +575,20 @@ static PyObject* serialize_task(PyObject* self, PyObject* args) {
     RAY_LOG(RAY_REFCOUNT, "In serialize_task, calling increment_reference_count for contained objrefs");
     worker->increment_reference_count(objrefs);
   }
+  std::string output;
+  task->SerializeToString(&output);
+  int task_size = output.length();
+  if (task_size > 1024) {
+    // Large objects should not be passed to tasks by value. Instead, they
+    // should be placed in the object store and passed by object
+    // reference.
+    RAY_LOG(RAY_INFO, "Warning: attempting to serialize a task with size " << task_size << ".");
+    PyErr_SetString(RaySizeError, "serialize_task: This task is too large (greater than 1024 bytes). "
+                                  "Please do not pass large objects by value to remote functions. "
+                                  "Instead, put large objects in the object store and pass them by "
+                                  "object reference to the remote function.");
+    return NULL;
+  }
   return PyCapsule_New(static_cast<void*>(task), "task", &TaskCapsule_Destructor);
 }
 
@@ -935,9 +950,13 @@ PyMODINIT_FUNC initlibraylib(void) {
   Py_INCREF(&PyObjRefType);
   PyModule_AddObject(m, "ObjRef", (PyObject *)&PyObjRefType);
   char ray_error[] = "ray.error";
+  char ray_size_error[] = "ray_size.error";
   RayError = PyErr_NewException(ray_error, NULL, NULL);
+  RaySizeError = PyErr_NewException(ray_size_error, NULL, NULL);
   Py_INCREF(RayError);
-  PyModule_AddObject(m, "error", RayError);
+  Py_INCREF(RaySizeError);
+  PyModule_AddObject(m, "ray_error", RayError);
+  PyModule_AddObject(m, "ray_size_error", RaySizeError);
   import_array();
 }
 

test/array_test.py

@@ -25,7 +25,7 @@ class RemoteArrayTest(unittest.TestCase):
     self.assertTrue(np.alltrue(val == np.zeros([3, 4, 5])))
 
     # test qr - pass by value
-    val_a = np.random.normal(size=[10, 13])
+    val_a = np.random.normal(size=[10, 11])
     ref_q, ref_r = ra.linalg.qr(val_a)
     val_q = ray.get(ref_q)
     val_r = ray.get(ref_r)