Refactor code about ray.ObjectID. (#3674)

* Refactor code about ray.ObjectID.

* remove from_random and use nil_id instead of constructor

* remove id() in hash

* Lint and fix

* Change driver id to ObjectID

* Replace binary_to_hex(ObjectID.id()) to ObjectID.hex()

src/ray/raylet/lib/python/common_extension.cc

@@ -30,8 +30,6 @@ using ray::UniqueID;
 using ray::FunctionID;
 using ray::TaskID;
 
-PyObject *CommonError;
-
 /* Initialize pickle module. */
 
 PyObject *pickle_module = NULL;
@@ -117,13 +115,18 @@ static int PyObjectID_init(PyObjectID *self, PyObject *args, PyObject *kwds) {
     return -1;
   }
   if (size != sizeof(ObjectID)) {
-    PyErr_SetString(CommonError, "ObjectID: object id string needs to have length 20");
+    PyErr_SetString(PyExc_ValueError,
+                    "ObjectID: object id string needs to have length 20");
     return -1;
   }
   std::memcpy(self->object_id.mutable_data(), data, sizeof(self->object_id));
   return 0;
 }
 
+static PyObject *PyObjectID_nil_id(PyObject *cls) {
+  return PyObjectID_make(ray::UniqueID());
+}
+
 /* Create a PyObjectID from C. */
 PyObject *PyObjectID_make(ObjectID object_id) {
   PyObjectID *result = PyObject_New(PyObjectID, &PyObjectIDType);
@@ -269,9 +272,14 @@ static PyObject *PyObjectID_repr(PyObjectID *self) {
   return result;
 }
 
-static PyObject *PyObjectID___reduce__(PyObjectID *self) {
-  PyErr_SetString(CommonError, "ObjectID objects cannot be serialized.");
-  return NULL;
+static PyObject *PyObjectID_getstate(PyObjectID *self) {
+  PyObject *field;
+  field = PyBytes_FromStringAndSize((char *)self->object_id.data(), sizeof(ObjectID));
+  return Py_BuildValue("(N)", field);
+}
+
+static PyObject *PyObjectID___reduce__(PyObjectID *self, PyObject *arg) {
+  return Py_BuildValue("(ON)", Py_TYPE(self), PyObjectID_getstate(self));
 }
 
 static PyMethodDef PyObjectID_methods[] = {
@@ -283,9 +291,10 @@ static PyMethodDef PyObjectID_methods[] = {
      "Return the object ID as a string in hex."},
     {"is_nil", (PyCFunction)PyObjectID_is_nil, METH_NOARGS,
      "Return whether the ObjectID is nil"},
-    {"__reduce__", (PyCFunction)PyObjectID___reduce__, METH_NOARGS,
-     "Say how to pickle this ObjectID. This raises an exception to prevent"
-     "object IDs from being serialized."},
+    {"__reduce__", (PyCFunction)PyObjectID___reduce__, METH_VARARGS,
+     "Provide a way to pickle this ObjectID."},
+    {"nil_id", (PyCFunction)PyObjectID_nil_id, METH_NOARGS | METH_CLASS,
+     "Create an instance of ray.ObjectID from random string"},
     {NULL} /* Sentinel */
 };
 
@@ -293,9 +302,11 @@ static PyMemberDef PyObjectID_members[] = {
     {NULL} /* Sentinel */
 };
 
+// This python class is introduced by python/ray/raylet/__init__.py.
+// Therefore, tp_name should match the path. ray.ObjectID is also OK.
 PyTypeObject PyObjectIDType = {
     PyVarObject_HEAD_INIT(NULL, 0)       /* ob_size */
-    "common.ObjectID",                   /* tp_name */
+    "ray.raylet.ObjectID",               /* tp_name */
     sizeof(PyObjectID),                  /* tp_basicsize */
     0,                                   /* tp_itemsize */
     0,                                   /* tp_dealloc */

src/ray/raylet/lib/python/common_extension.h

@@ -12,7 +12,7 @@
 typedef char TaskSpec;
 class TaskBuilder;
 
-extern PyObject *CommonError;
+extern PyObject *ray_common_error;
 
 // clang-format off
 typedef struct {

src/ray/raylet/lib/python/raylet_extension.cc

@@ -31,6 +31,8 @@ static int PyRayletClient_init(PyRayletClient *self, PyObject *args, PyObject *k
   return 0;
 }
 
+PyObject *ray_common_error = nullptr;
+
 static void PyRayletClient_dealloc(PyRayletClient *self) {
   if (self->raylet_client != NULL) {
     delete self->raylet_client;
@@ -112,7 +114,7 @@ static PyObject *PyRayletClient_FetchOrReconstruct(PyRayletClient *self, PyObjec
     stream << "[RayletClient] FetchOrReconstruct failed: "
            << "raylet client may be closed, check raylet status. error message: "
            << status.ToString();
-    PyErr_SetString(CommonError, stream.str().c_str());
+    PyErr_SetString(ray_common_error, stream.str().c_str());
     return NULL;
   }
 }
@@ -485,9 +487,9 @@ MOD_INIT(libraylet_library_python) {
   PyModule_AddObject(m, "RayletClient", (PyObject *)&PyRayletClientType);
 
   char common_error[] = "common.error";
-  CommonError = PyErr_NewException(common_error, NULL, NULL);
-  Py_INCREF(CommonError);
-  PyModule_AddObject(m, "common_error", CommonError);
+  ray_common_error = PyErr_NewException(common_error, NULL, NULL);
+  Py_INCREF(ray_common_error);
+  PyModule_AddObject(m, "RayCommonError", ray_common_error);
 
   Py_INCREF(&PyRayConfigType);
   PyModule_AddObject(m, "RayConfig", (PyObject *)&PyRayConfigType);