Method load_subclass_of

src/mgr/PyModule.cc:725–783

}

int PyModule::load_subclass_of(const char* base_class, PyObject** py_class)
{
  // load the base class
  PyObject *mgr_module = PyImport_ImportModule("mgr_module");
  if (!mgr_module) {
    error_string = peek_pyerror();
    derr << "Module not found: 'mgr_module'" << dendl;
    derr << handle_pyerror(true, module_name, "PyModule::load_subclass_of") << dendl;
    return -EINVAL;
  }
  auto mgr_module_type = PyObject_GetAttrString(mgr_module, base_class);
  Py_DECREF(mgr_module);
  if (!mgr_module_type) {
    error_string = peek_pyerror();
    derr << "Unable to import MgrModule from mgr_module" << dendl;
    derr << handle_pyerror(true, module_name, "PyModule::load_subclass_of") << dendl;
    return -EINVAL;
  }

  // find the sub class
  PyObject *plugin_module = PyImport_ImportModule(module_name.c_str());
  if (!plugin_module) {
    error_string = peek_pyerror();
    derr << "Module not found: '" << module_name << "'" << dendl;
    derr << handle_pyerror(true, module_name, "PyModule::load_subclass_of") << dendl;
    Py_DECREF(mgr_module_type);
    return -ENOENT;
  }
  auto locals = PyModule_GetDict(plugin_module);
  Py_DECREF(plugin_module);
  PyObject *key, *value;
  Py_ssize_t pos = 0;
  *py_class = nullptr;
  while (PyDict_Next(locals, &pos, &key, &value)) {
    if (!PyType_Check(value)) {
      continue;
    }
    if (!PyObject_IsSubclass(value, mgr_module_type)) {
      continue;
    }
    if (PyObject_RichCompareBool(value, mgr_module_type, Py_EQ)) {
      continue;
    }
    auto class_name = PyUnicode_AsUTF8(key);
    if (*py_class) {
      derr << __func__ << ": ignoring '"
	   << module_name << "." << class_name << "'"
	   << ": only one '" << base_class
	   << "' class is loaded from each plugin" << dendl;
      continue;
    }
    *py_class = value;
    dout(4) << __func__ << ": found class: '"
	    << module_name << "." << class_name << "'" << dendl;
  }
  Py_DECREF(mgr_module_type);

  return *py_class ? 0 : -EINVAL;