mgr: stop using deprecated API to initialize Python

Py_SetProgramName() is deprecated since CPython 3.11, see
https://docs.python.org/3/c-api/init_config.html .
`Py_InitializeFromConfig()` and friends were introduced by CPython 3.8,
but we still need to support CPython 3.6 which is shipped by CentOS8.
so we have to be backward compatible with the older Python versions.

so let's use new machinary to initialize the Python interpretor, since
the minimal supported Python version is now CPython 3.9 which comes with
CentOS 9.

this change addresses following compiling warning:

```
[428/753] Building CXX object src/mgr/CMakeFiles/ceph-mgr.dir/PyModuleRegistry.cc.o
/var/ssd/ceph/src/mgr/PyModuleRegistry.cc: In member function ‘void PyModuleRegistry::init()’:
/var/ssd/ceph/src/mgr/PyModuleRegistry.cc:49:20: warning: ‘void Py_SetProgramName(const wchar_t*)’ is deprecated [-Wdeprecated-declarations]
   49 |   Py_SetProgramName(const_cast<wchar_t*>(WCHAR(MGR_PYTHON_EXECUTABLE)));
      |   ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/python3.12/Python.h:94,
                 from /var/ssd/ceph/src/mgr/PyModule.h:22,
                 from /var/ssd/ceph/src/mgr/PyModuleRegistry.h:18,
                 from /var/ssd/ceph/src/mgr/PyModuleRegistry.cc:14:
/usr/include/python3.12/pylifecycle.h:37:38: note: declared here
   37 | Py_DEPRECATED(3.11) PyAPI_FUNC(void) Py_SetProgramName(const wchar_t *);
      |                                      ^~~~~~~~~~~~~~~~~`
```

Signed-off-by: Kefu Chai <tchaikov@gmail.com>
(cherry picked from commit 4cf9b36c66fd64f2dc50f4e1acca3fe93e29b3f2)

diff --git a/src/mgr/PyModuleRegistry.cc b/src/mgr/PyModuleRegistry.cc
index 407f3f8adb895862da7932d88b23535b1630877c..b04796e46bf6be116f15a61cbda02121affd34ea 100644 (file)
--- a/src/mgr/PyModuleRegistry.cc
+++ b/src/mgr/PyModuleRegistry.cc
@@ -14,6 +14,7 @@
 #include "PyModuleRegistry.h"
 
 #include <filesystem>
+#include <boost/scope_exit.hpp>
 
 #include "include/stringify.h"
 #include "common/errno.h"
@@ -46,21 +47,37 @@ void PyModuleRegistry::init()
 
   // Set up global python interpreter
 #define WCHAR(s) L ## #s
-  Py_SetProgramName(const_cast<wchar_t*>(WCHAR(MGR_PYTHON_EXECUTABLE)));
-#undef WCHAR
+  PyConfig py_config;
+  // do not enable isolated mode, otherwise we would not be able to have access
+  // to the site packages. since we cannot import any module before initializing
+  // the interpreter, we would not be able to use "site" module for retrieving
+  // the path to site packager. we import "site" module for retrieving
+  // sitepackages in Python < 3.8 though, this does not apply to the
+  // initialization with PyConfig.
+  PyConfig_InitPythonConfig(&py_config);
+  BOOST_SCOPE_EXIT_ALL(&py_config) {
+    PyConfig_Clear(&py_config);
+  };
+#if PY_VERSION_HEX >= 0x030b0000
+  py_config.safe_path = 0;
+#endif
+  py_config.parse_argv = 0;
+  py_config.configure_c_stdio = 0;
+  py_config.install_signal_handlers = 0;
+  py_config.pathconfig_warnings = 0;
+
+  PyStatus status;
+  status = PyConfig_SetString(&py_config, &py_config.program_name, WCHAR(MGR_PYTHON_EXECUTABLE));
+  ceph_assertf(!PyStatus_Exception(status), "PyConfig_SetString: %s:%s", status.func, status.err_msg);
   // Add more modules
   if (g_conf().get_val<bool>("daemonize")) {
     PyImport_AppendInittab("ceph_logger", PyModule::init_ceph_logger);
   }
   PyImport_AppendInittab("ceph_module", PyModule::init_ceph_module);
-  Py_InitializeEx(0);
-#if PY_VERSION_HEX < 0x03090000
-  // Let CPython know that we will be calling it back from other
-  // threads in future.
-  if (! PyEval_ThreadsInitialized()) {
-    PyEval_InitThreads();
-  }
-#endif
+  status = Py_InitializeFromConfig(&py_config);
+  ceph_assertf(!PyStatus_Exception(status), "Py_InitializeFromConfig: %s:%s", status.func, status.err_msg);
+#undef WCHAR
+
   // Drop the GIL and remember the main thread state (current
   // thread state becomes NULL)
   pMainThreadState = PyEval_SaveThread();