Adding upstream version 16.2.11+ds.upstream/16.2.11+dsupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 729 insertions, 0 deletions

diff --git a/src/mgr/PyModule.cc b/src/mgr/PyModule.cc
new file mode 100644
index 000000000..19d02332d
--- /dev/null
+++ b/src/mgr/PyModule.cc
@@ -0,0 +1,729 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2017 John Spray <john.spray@redhat.com>
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software
+ * Foundation.  See file COPYING.
+ */
+
+#include "BaseMgrModule.h"
+#include "BaseMgrStandbyModule.h"
+#include "PyOSDMap.h"
+#include "MgrContext.h"
+#include "PyUtil.h"
+
+#include "PyModule.h"
+
+#include "common/debug.h"
+#include "common/errno.h"
+#define dout_context g_ceph_context
+#define dout_subsys ceph_subsys_mgr
+
+#undef dout_prefix
+#define dout_prefix *_dout << "mgr[py] "
+
+// definition for non-const static member
+std::string PyModule::mgr_store_prefix = "mgr/";
+
+// Courtesy of http://stackoverflow.com/questions/1418015/how-to-get-python-exception-text
+#define BOOST_BIND_GLOBAL_PLACEHOLDERS
+// Boost apparently can't be bothered to fix its own usage of its own
+// deprecated features.
+#include <boost/python/extract.hpp>
+#include <boost/python/import.hpp>
+#include <boost/python/object.hpp>
+#undef BOOST_BIND_GLOBAL_PLACEHOLDERS
+#include <boost/algorithm/string/predicate.hpp>
+#include "include/ceph_assert.h"  // boost clobbers this
+// decode a Python exception into a string
+std::string handle_pyerror()
+{
+    using namespace boost::python;
+    using namespace boost;
+
+    PyObject *exc, *val, *tb;
+    object formatted_list, formatted;
+    PyErr_Fetch(&exc, &val, &tb);
+    PyErr_NormalizeException(&exc, &val, &tb);
+    handle<> hexc(exc), hval(allow_null(val)), htb(allow_null(tb));
+    object traceback(import("traceback"));
+    if (!tb) {
+        object format_exception_only(traceback.attr("format_exception_only"));
+        try {
+          formatted_list = format_exception_only(hexc, hval);
+        } catch (error_already_set const &) {
+          // error while processing exception object
+          // returning only the exception string value
+          PyObject *name_attr = PyObject_GetAttrString(exc, "__name__");
+          std::stringstream ss;
+          ss << PyUnicode_AsUTF8(name_attr) << ": " << PyUnicode_AsUTF8(val);
+          Py_XDECREF(name_attr);
+          ss << "\nError processing exception object: " << peek_pyerror();
+          return ss.str();
+        }
+    } else {
+        object format_exception(traceback.attr("format_exception"));
+        try {
+          formatted_list = format_exception(hexc, hval, htb);
+        } catch (error_already_set const &) {
+          // error while processing exception object
+          // returning only the exception string value
+          PyObject *name_attr = PyObject_GetAttrString(exc, "__name__");
+          std::stringstream ss;
+          ss << PyUnicode_AsUTF8(name_attr) << ": " << PyUnicode_AsUTF8(val);
+          Py_XDECREF(name_attr);
+          ss << "\nError processing exception object: " << peek_pyerror();
+          return ss.str();
+        }
+    }
+    formatted = str("").join(formatted_list);
+    return extract<std::string>(formatted);
+}
+
+/**
+ * Get the single-line exception message, without clearing any
+ * exception state.
+ */
+std::string peek_pyerror()
+{
+  PyObject *ptype, *pvalue, *ptraceback;
+  PyErr_Fetch(&ptype, &pvalue, &ptraceback);
+  ceph_assert(ptype);
+  ceph_assert(pvalue);
+  PyObject *pvalue_str = PyObject_Str(pvalue);
+  std::string exc_msg = PyUnicode_AsUTF8(pvalue_str);
+  Py_DECREF(pvalue_str);
+  PyErr_Restore(ptype, pvalue, ptraceback);
+
+  return exc_msg;
+}
+
+
+namespace {
+  PyObject* log_write(PyObject*, PyObject* args) {
+    char* m = nullptr;
+    if (PyArg_ParseTuple(args, "s", &m)) {
+      auto len = strlen(m);
+      if (len && m[len-1] == '\n') {
+	m[len-1] = '\0';
+      }
+      dout(4) << m << dendl;
+    }
+    Py_RETURN_NONE;
+  }
+
+  PyObject* log_flush(PyObject*, PyObject*){
+    Py_RETURN_NONE;
+  }
+
+  static PyMethodDef log_methods[] = {
+    {"write", log_write, METH_VARARGS, "write stdout and stderr"},
+    {"flush", log_flush, METH_VARARGS, "flush"},
+    {nullptr, nullptr, 0, nullptr}
+  };
+
+  static PyModuleDef ceph_logger_module = {
+    PyModuleDef_HEAD_INIT,
+    "ceph_logger",
+    nullptr,
+    -1,
+    log_methods,
+  };
+}
+
+PyModuleConfig::PyModuleConfig() = default;  
+
+PyModuleConfig::PyModuleConfig(PyModuleConfig &mconfig)
+  : config(mconfig.config)
+{}
+
+PyModuleConfig::~PyModuleConfig() = default;
+
+
+void PyModuleConfig::set_config(
+    MonClient *monc,
+    const std::string &module_name,
+    const std::string &key, const boost::optional<std::string>& val)
+{
+  const std::string global_key = "mgr/" + module_name + "/" + key;
+  Command set_cmd;
+  {
+    std::ostringstream cmd_json;
+    JSONFormatter jf;
+    jf.open_object_section("cmd");
+    if (val) {
+      jf.dump_string("prefix", "config set");
+      jf.dump_string("value", *val);
+    } else {
+      jf.dump_string("prefix", "config rm");
+    }
+    jf.dump_string("who", "mgr");
+    jf.dump_string("name", global_key);
+    jf.close_section();
+    jf.flush(cmd_json);
+    set_cmd.run(monc, cmd_json.str());
+  }
+  set_cmd.wait();
+
+  if (set_cmd.r == 0) {
+    std::lock_guard l(lock);
+    if (val) {
+      config[global_key] = *val;
+    } else {
+      config.erase(global_key);
+    }
+  } else {
+    if (val) {
+      dout(0) << "`config set mgr " << global_key << " " << val << "` failed: "
+        << cpp_strerror(set_cmd.r) << dendl;
+    } else {
+      dout(0) << "`config rm mgr " << global_key << "` failed: "
+        << cpp_strerror(set_cmd.r) << dendl;
+    }
+    dout(0) << "mon returned " << set_cmd.r << ": " << set_cmd.outs << dendl;
+  }
+}
+
+std::string PyModule::get_site_packages()
+{
+  std::stringstream site_packages;
+
+  // CPython doesn't auto-add site-packages dirs to sys.path for us,
+  // but it does provide a module that we can ask for them.
+  auto site_module = PyImport_ImportModule("site");
+  ceph_assert(site_module);
+
+  auto site_packages_fn = PyObject_GetAttrString(site_module, "getsitepackages");
+  if (site_packages_fn != nullptr) {
+    auto site_packages_list = PyObject_CallObject(site_packages_fn, nullptr);
+    ceph_assert(site_packages_list);
+
+    auto n = PyList_Size(site_packages_list);
+    for (Py_ssize_t i = 0; i < n; ++i) {
+      if (i != 0) {
+        site_packages << ":";
+      }
+      site_packages << PyUnicode_AsUTF8(PyList_GetItem(site_packages_list, i));
+    }
+
+    Py_DECREF(site_packages_list);
+    Py_DECREF(site_packages_fn);
+  } else {
+    // Fall back to generating our own site-packages paths by imitating
+    // what the standard site.py does.  This is annoying but it lets us
+    // run inside virtualenvs :-/
+
+    auto site_packages_fn = PyObject_GetAttrString(site_module, "addsitepackages");
+    ceph_assert(site_packages_fn);
+
+    auto known_paths = PySet_New(nullptr);
+    auto pArgs = PyTuple_Pack(1, known_paths);
+    PyObject_CallObject(site_packages_fn, pArgs);
+    Py_DECREF(pArgs);
+    Py_DECREF(known_paths);
+    Py_DECREF(site_packages_fn);
+
+    auto sys_module = PyImport_ImportModule("sys");
+    ceph_assert(sys_module);
+    auto sys_path = PyObject_GetAttrString(sys_module, "path");
+    ceph_assert(sys_path);
+
+    dout(1) << "sys.path:" << dendl;
+    auto n = PyList_Size(sys_path);
+    bool first = true;
+    for (Py_ssize_t i = 0; i < n; ++i) {
+      dout(1) << "  " << PyUnicode_AsUTF8(PyList_GetItem(sys_path, i)) << dendl;
+      if (first) {
+        first = false;
+      } else {
+        site_packages << ":";
+      }
+      site_packages << PyUnicode_AsUTF8(PyList_GetItem(sys_path, i));
+    }
+
+    Py_DECREF(sys_path);
+    Py_DECREF(sys_module);
+  }
+
+  Py_DECREF(site_module);
+
+  return site_packages.str();
+}
+
+PyObject* PyModule::init_ceph_logger()
+{
+  auto py_logger = PyModule_Create(&ceph_logger_module);
+  PySys_SetObject("stderr", py_logger);
+  PySys_SetObject("stdout", py_logger);
+  return py_logger;
+}
+
+PyObject* PyModule::init_ceph_module()
+{
+  static PyMethodDef module_methods[] = {
+    {nullptr, nullptr, 0, nullptr}
+  };
+  static PyModuleDef ceph_module_def = {
+    PyModuleDef_HEAD_INIT,
+    "ceph_module",
+    nullptr,
+    -1,
+    module_methods,
+    nullptr,
+    nullptr,
+    nullptr,
+    nullptr
+  };
+  PyObject *ceph_module = PyModule_Create(&ceph_module_def);
+  ceph_assert(ceph_module != nullptr);
+  std::map<const char*, PyTypeObject*> classes{
+    {{"BaseMgrModule", &BaseMgrModuleType},
+     {"BaseMgrStandbyModule", &BaseMgrStandbyModuleType},
+     {"BasePyOSDMap", &BasePyOSDMapType},
+     {"BasePyOSDMapIncremental", &BasePyOSDMapIncrementalType},
+     {"BasePyCRUSH", &BasePyCRUSHType}}
+  };
+  for (auto [name, type] : classes) {
+    type->tp_new = PyType_GenericNew;
+    if (PyType_Ready(type) < 0) {
+      ceph_abort();
+    }
+    Py_INCREF(type);
+
+    PyModule_AddObject(ceph_module, name, (PyObject *)type);
+  }
+  return ceph_module;
+}
+
+int PyModule::load(PyThreadState *pMainThreadState)
+{
+  ceph_assert(pMainThreadState != nullptr);
+
+  // Configure sub-interpreter
+  {
+    SafeThreadState sts(pMainThreadState);
+    Gil gil(sts);
+
+    auto thread_state = Py_NewInterpreter();
+    if (thread_state == nullptr) {
+      derr << "Failed to create python sub-interpreter for '" << module_name << '"' << dendl;
+      return -EINVAL;
+    } else {
+      pMyThreadState.set(thread_state);
+      // Some python modules do not cope with an unpopulated argv, so lets
+      // fake one.  This step also picks up site-packages into sys.path.
+      const wchar_t *argv[] = {L"ceph-mgr"};
+      PySys_SetArgv(1, (wchar_t**)argv);
+      // Configure sys.path to include mgr_module_path
+      string paths = (g_conf().get_val<std::string>("mgr_module_path") + ':' +
+                      get_site_packages() + ':');
+      wstring sys_path(wstring(begin(paths), end(paths)) + Py_GetPath());
+      PySys_SetPath(const_cast<wchar_t*>(sys_path.c_str()));
+      dout(10) << "Computed sys.path '"
+	       << string(begin(sys_path), end(sys_path)) << "'" << dendl;
+    }
+  }
+  // Environment is all good, import the external module
+  {
+    Gil gil(pMyThreadState);
+
+    int r;
+    r = load_subclass_of("MgrModule", &pClass);
+    if (r) {
+      derr << "Class not found in module '" << module_name << "'" << dendl;
+      return r;
+    }
+
+    r = load_commands();
+    if (r != 0) {
+      derr << "Missing or invalid COMMANDS attribute in module '"
+          << module_name << "'" << dendl;
+      error_string = "Missing or invalid COMMANDS attribute";
+      return r;
+    }
+
+    register_options(pClass);
+    r = load_options();
+    if (r != 0) {
+      derr << "Missing or invalid MODULE_OPTIONS attribute in module '"
+          << module_name << "'" << dendl;
+      error_string = "Missing or invalid MODULE_OPTIONS attribute";
+      return r;
+    }
+
+    load_notify_types();
+
+    // We've imported the module and found a MgrModule subclass, at this
+    // point the module is considered loaded.  It might still not be
+    // runnable though, can_run populated later...
+    loaded = true;
+
+    r = load_subclass_of("MgrStandbyModule", &pStandbyClass);
+    if (!r) {
+      dout(4) << "Standby mode available in module '" << module_name
+              << "'" << dendl;
+      register_options(pStandbyClass);
+    } else {
+      dout(4) << "Standby mode not provided by module '" << module_name
+              << "'" << dendl;
+    }
+
+    // Populate can_run by interrogating the module's callback that
+    // may check for dependencies etc
+    PyObject *pCanRunTuple = PyObject_CallMethod(pClass,
+      const_cast<char*>("can_run"), const_cast<char*>("()"));
+    if (pCanRunTuple != nullptr) {
+      if (PyTuple_Check(pCanRunTuple) && PyTuple_Size(pCanRunTuple) == 2) {
+        PyObject *pCanRun = PyTuple_GetItem(pCanRunTuple, 0);
+        PyObject *can_run_str = PyTuple_GetItem(pCanRunTuple, 1);
+        if (!PyBool_Check(pCanRun) || !PyUnicode_Check(can_run_str)) {
+          derr << "Module " << get_name()
+               << " returned wrong type in can_run" << dendl;
+          error_string = "wrong type returned from can_run";
+          can_run = false;
+        } else {
+          can_run = (pCanRun == Py_True);
+          if (!can_run) {
+            error_string = PyUnicode_AsUTF8(can_run_str);
+            dout(4) << "Module " << get_name()
+                    << " reported that it cannot run: "
+                    << error_string << dendl;
+          }
+        }
+      } else {
+        derr << "Module " << get_name()
+             << " returned wrong type in can_run" << dendl;
+        error_string = "wrong type returned from can_run";
+        can_run = false;
+      }
+
+      Py_DECREF(pCanRunTuple);
+    } else {
+      derr << "Exception calling can_run on " << get_name() << dendl;
+      derr << handle_pyerror() << dendl;
+      can_run = false;
+    }
+  }
+  return 0;
+}
+
+int PyModule::walk_dict_list(
+    const std::string &attr_name,
+    std::function<int(PyObject*)> fn)
+{
+  PyObject *command_list = PyObject_GetAttrString(pClass, attr_name.c_str());
+  if (command_list == nullptr) {
+    derr << "Module " << get_name() << " has missing " << attr_name
+         << " member" << dendl;
+    return -EINVAL;
+  }
+  if (!PyObject_TypeCheck(command_list, &PyList_Type)) {
+    // Relatively easy mistake for human to make, e.g. defining COMMANDS
+    // as a {} instead of a []
+    derr << "Module " << get_name() << " has " << attr_name
+         << " member of wrong type (should be a list)" << dendl;
+    return -EINVAL;
+  }
+
+  // Invoke fn on each item in the list
+  int r = 0;
+  const size_t list_size = PyList_Size(command_list);
+  for (size_t i = 0; i < list_size; ++i) {
+    PyObject *command = PyList_GetItem(command_list, i);
+    ceph_assert(command != nullptr);
+
+    if (!PyDict_Check(command)) {
+      derr << "Module " << get_name() << " has non-dict entry "
+           << "in " << attr_name << " list" << dendl;
+      return -EINVAL;
+    }
+
+    r = fn(command);
+    if (r != 0) {
+      break;
+    }
+  }
+  Py_DECREF(command_list);
+
+  return r;
+}
+
+int PyModule::register_options(PyObject *cls)
+{
+  PyObject *pRegCmd = PyObject_CallMethod(
+    cls,
+    const_cast<char*>("_register_options"), const_cast<char*>("(s)"),
+      module_name.c_str());
+  if (pRegCmd != nullptr) {
+    Py_DECREF(pRegCmd);
+  } else {
+    derr << "Exception calling _register_options on " << get_name()
+         << dendl;
+    derr << handle_pyerror() << dendl;
+  }
+  return 0;
+}
+
+int PyModule::load_notify_types()
+{
+  PyObject *ls = PyObject_GetAttrString(pClass, "NOTIFY_TYPES");
+  if (ls == nullptr) {
+    derr << "Module " << get_name() << " has missing NOTIFY_TYPES member" << dendl;
+    return -EINVAL;
+  }
+  if (!PyObject_TypeCheck(ls, &PyList_Type)) {
+    // Relatively easy mistake for human to make, e.g. defining COMMANDS
+    // as a {} instead of a []
+    derr << "Module " << get_name() << " has NOTIFY_TYPES that is not a list" << dendl;
+    return -EINVAL;
+  }
+
+  const size_t list_size = PyList_Size(ls);
+  for (size_t i = 0; i < list_size; ++i) {
+    PyObject *notify_type = PyList_GetItem(ls, i);
+    ceph_assert(notify_type != nullptr);
+
+    if (!PyObject_TypeCheck(notify_type, &PyUnicode_Type)) {
+      derr << "Module " << get_name() << " has non-string entry in NOTIFY_TYPES list"
+	   << dendl;
+      return -EINVAL;
+    }
+
+    notify_types.insert(PyUnicode_AsUTF8(notify_type));
+  }
+  Py_DECREF(ls);
+  dout(10) << "Module " << get_name() << " notify_types " << notify_types << dendl;
+
+  return 0;
+}
+
+int PyModule::load_commands()
+{
+  PyObject *pRegCmd = PyObject_CallMethod(pClass,
+      const_cast<char*>("_register_commands"), const_cast<char*>("(s)"),
+      module_name.c_str());
+  if (pRegCmd != nullptr) {
+    Py_DECREF(pRegCmd);
+  } else {
+    derr << "Exception calling _register_commands on " << get_name()
+         << dendl;
+    derr << handle_pyerror() << dendl;
+  }
+
+  int r = walk_dict_list("COMMANDS", [this](PyObject *pCommand) -> int {
+    ModuleCommand command;
+
+    PyObject *pCmd = PyDict_GetItemString(pCommand, "cmd");
+    ceph_assert(pCmd != nullptr);
+    command.cmdstring = PyUnicode_AsUTF8(pCmd);
+
+    dout(20) << "loaded command " << command.cmdstring << dendl;
+
+    PyObject *pDesc = PyDict_GetItemString(pCommand, "desc");
+    ceph_assert(pDesc != nullptr);
+    command.helpstring = PyUnicode_AsUTF8(pDesc);
+
+    PyObject *pPerm = PyDict_GetItemString(pCommand, "perm");
+    ceph_assert(pPerm != nullptr);
+    command.perm = PyUnicode_AsUTF8(pPerm);
+
+    command.polling = false;
+    if (PyObject *pPoll = PyDict_GetItemString(pCommand, "poll");
+	pPoll && PyObject_IsTrue(pPoll)) {
+      command.polling = true;
+    }
+
+    command.module_name = module_name;
+
+    commands.push_back(std::move(command));
+
+    return 0;
+  });
+
+  dout(10) << "loaded " << commands.size() << " commands" << dendl;
+
+  return r;
+}
+
+int PyModule::load_options()
+{
+  int r = walk_dict_list("MODULE_OPTIONS", [this](PyObject *pOption) -> int {
+    MgrMap::ModuleOption option;
+    PyObject *p;
+    p = PyDict_GetItemString(pOption, "name");
+    ceph_assert(p != nullptr);
+    option.name = PyUnicode_AsUTF8(p);
+    option.type = Option::TYPE_STR;
+    p = PyDict_GetItemString(pOption, "type");
+    if (p && PyObject_TypeCheck(p, &PyUnicode_Type)) {
+      std::string s = PyUnicode_AsUTF8(p);
+      int t = Option::str_to_type(s);
+      if (t >= 0) {
+	option.type = t;
+      }
+    }
+    p = PyDict_GetItemString(pOption, "desc");
+    if (p && PyObject_TypeCheck(p, &PyUnicode_Type)) {
+      option.desc = PyUnicode_AsUTF8(p);
+    }
+    p = PyDict_GetItemString(pOption, "long_desc");
+    if (p && PyObject_TypeCheck(p, &PyUnicode_Type)) {
+      option.long_desc = PyUnicode_AsUTF8(p);
+    }
+    p = PyDict_GetItemString(pOption, "default");
+    if (p) {
+      auto q = PyObject_Str(p);
+      option.default_value = PyUnicode_AsUTF8(q);
+      Py_DECREF(q);
+    }
+    p = PyDict_GetItemString(pOption, "min");
+    if (p) {
+      auto q = PyObject_Str(p);
+      option.min = PyUnicode_AsUTF8(q);
+      Py_DECREF(q);
+    }
+    p = PyDict_GetItemString(pOption, "max");
+    if (p) {
+      auto q = PyObject_Str(p);
+      option.max = PyUnicode_AsUTF8(q);
+      Py_DECREF(q);
+    }
+    p = PyDict_GetItemString(pOption, "enum_allowed");
+    if (p && PyObject_TypeCheck(p, &PyList_Type)) {
+      for (unsigned i = 0; i < PyList_Size(p); ++i) {
+	auto q = PyList_GetItem(p, i);
+	if (q) {
+	  auto r = PyObject_Str(q);
+	  option.enum_allowed.insert(PyUnicode_AsUTF8(r));
+	  Py_DECREF(r);
+	}
+      }
+    }
+    p = PyDict_GetItemString(pOption, "see_also");
+    if (p && PyObject_TypeCheck(p, &PyList_Type)) {
+      for (unsigned i = 0; i < PyList_Size(p); ++i) {
+	auto q = PyList_GetItem(p, i);
+	if (q && PyObject_TypeCheck(q, &PyUnicode_Type)) {
+	  option.see_also.insert(PyUnicode_AsUTF8(q));
+	}
+      }
+    }
+    p = PyDict_GetItemString(pOption, "tags");
+    if (p && PyObject_TypeCheck(p, &PyList_Type)) {
+      for (unsigned i = 0; i < PyList_Size(p); ++i) {
+	auto q = PyList_GetItem(p, i);
+	if (q && PyObject_TypeCheck(q, &PyUnicode_Type)) {
+	  option.tags.insert(PyUnicode_AsUTF8(q));
+	}
+      }
+    }
+    p = PyDict_GetItemString(pOption, "runtime");
+    if (p && PyObject_TypeCheck(p, &PyBool_Type)) {
+      if (p == Py_True) {
+	option.flags |= Option::FLAG_RUNTIME;
+      }
+      if (p == Py_False) {
+	option.flags &= ~Option::FLAG_RUNTIME;
+      }
+    }
+    dout(20) << "loaded module option " << option.name << dendl;
+    options[option.name] = std::move(option);
+    return 0;
+  });
+
+  dout(10) << "loaded " << options.size() << " options" << dendl;
+
+  return r;
+}
+
+bool PyModule::is_option(const std::string &option_name)
+{
+  std::lock_guard l(lock);
+  return options.count(option_name) > 0;
+}
+
+PyObject *PyModule::get_typed_option_value(const std::string& name,
+					   const std::string& value)
+{
+  // we don't need to hold a lock here because these MODULE_OPTIONS
+  // are set up exactly once during startup.
+  auto p = options.find(name);
+  if (p != options.end()) {
+    return get_python_typed_option_value((Option::type_t)p->second.type, value);
+  }
+  return PyUnicode_FromString(value.c_str());
+}
+
+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() << 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() << 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() << dendl;
+    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;
+}
+
+PyModule::~PyModule()
+{
+  if (pMyThreadState.ts != nullptr) {
+    Gil gil(pMyThreadState, true);
+    Py_XDECREF(pClass);
+    Py_XDECREF(pStandbyClass);
+  }
+}
+