FreeBSD: fix for get_linux_distro() and lru_cache (#59)

Since `is_FreeBSD()` is used a lot, which uses `system_info()`, which uses `get_linux_distro()` we add caching, by decorating the following functions with `@lru_cache`:

- get_architecture()
- _lsb_release()
- is_FreeBSD
- get_linux_distro
- system_info()
- _get_cmdline()

Since [functools](https://docs.python.org/3/library/functools.html) only exists in Python 3, only python 3 will benefit from this improvement. For python 2, our shim is just a pass-thru. Too bad, but, also… https://pythonclock.org/

The main motivation here was, at first, to cache more, following the style of _lsb_release.
That is now consolidated under this very same roof.

LP: #1815030

3 files changed, 61 insertions, 24 deletions

diff --git a/cloudinit/tests/test_util.py b/cloudinit/tests/test_util.py
index f4f95e92..64ed82ea 100644
--- a/cloudinit/tests/test_util.py
+++ b/cloudinit/tests/test_util.py
@@ -387,6 +387,11 @@ class TestUdevadmSettle(CiTestCase):
 @mock.patch('os.path.exists')
 class TestGetLinuxDistro(CiTestCase):
 
+    def setUp(self):
+        # python2 has no lru_cache, and therefore, no cache_clear()
+        if hasattr(util.get_linux_distro, "cache_clear"):
+            util.get_linux_distro.cache_clear()
+
     @classmethod
     def os_release_exists(self, path):
         """Side effect function"""
@@ -399,6 +404,12 @@ class TestGetLinuxDistro(CiTestCase):
         if path == '/etc/redhat-release':
             return 1
 
+    @classmethod
+    def freebsd_version_exists(self, path):
+        """Side effect function """
+        if path == '/bin/freebsd-version':
+            return 1
+
     @mock.patch('cloudinit.util.load_file')
     def test_get_linux_distro_quoted_name(self, m_os_release, m_path_exists):
         """Verify we get the correct name if the os-release file has
@@ -417,6 +428,14 @@ class TestGetLinuxDistro(CiTestCase):
         dist = util.get_linux_distro()
         self.assertEqual(('ubuntu', '16.04', 'xenial'), dist)
 
+    @mock.patch('cloudinit.util.subp')
+    def test_get_linux_freebsd(self, m_subp, m_path_exists):
+        """Verify we get the correct name and release name on FreeBSD."""
+        m_path_exists.side_effect = TestGetLinuxDistro.freebsd_version_exists
+        m_subp.return_value = ("12.0-RELEASE-p10\n", '')
+        dist = util.get_linux_distro()
+        self.assertEqual(('freebsd', '12.0-RELEASE-p10', ''), dist)
+
     @mock.patch('cloudinit.util.load_file')
     def test_get_linux_centos6(self, m_os_release, m_path_exists):
         """Verify we get the correct name and release name on CentOS 6."""
diff --git a/cloudinit/util.py b/cloudinit/util.py
index 1f600df4..c498414d 100644
--- a/cloudinit/util.py
+++ b/cloudinit/util.py
@@ -50,6 +50,16 @@ from cloudinit import version
 
 from cloudinit.settings import (CFG_BUILTIN)
 
+try:
+    from functools import lru_cache
+except ImportError:
+    def lru_cache():
+        """pass-thru replace for Python3's lru_cache()"""
+        def wrapper(f):
+            return f
+        return wrapper
+
+
 _DNS_REDIRECT_IP = None
 LOG = logging.getLogger(__name__)
 
@@ -68,17 +78,15 @@ CONTAINER_TESTS = (['systemd-detect-virt', '--quiet', '--container'],
                    ['running-in-container'],
                    ['lxc-is-container'])
 
-PROC_CMDLINE = None
-
-_LSB_RELEASE = {}
-
 
+@lru_cache()
 def get_architecture(target=None):
     out, _ = subp(['dpkg', '--print-architecture'], capture=True,
                   target=target)
     return out.strip()
 
 
+@lru_cache()
 def _lsb_release(target=None):
     fmap = {'Codename': 'codename', 'Description': 'description',
             'Distributor ID': 'id', 'Release': 'release'}
@@ -107,11 +115,7 @@ def lsb_release(target=None):
         # do not use or update cache if target is provided
         return _lsb_release(target)
 
-    global _LSB_RELEASE
-    if not _LSB_RELEASE:
-        data = _lsb_release()
-        _LSB_RELEASE.update(data)
-    return _LSB_RELEASE
+    return _lsb_release()
 
 
 def target_path(target, path=None):
@@ -546,6 +550,7 @@ def is_ipv4(instr):
     return len(toks) == 4
 
 
+@lru_cache()
 def is_FreeBSD():
     return system_info()['variant'] == "freebsd"
 
@@ -595,6 +600,7 @@ def _parse_redhat_release(release_file=None):
     return {}
 
 
+@lru_cache()
 def get_linux_distro():
     distro_name = ''
     distro_version = ''
@@ -622,6 +628,10 @@ def get_linux_distro():
                     flavor = match.groupdict()['codename']
         if distro_name == 'rhel':
             distro_name = 'redhat'
+    elif os.path.exists('/bin/freebsd-version'):
+        distro_name = 'freebsd'
+        distro_version, _ = subp(['uname', '-r'])
+        distro_version = distro_version.strip()
     else:
         dist = ('', '', '')
         try:
@@ -642,6 +652,7 @@ def get_linux_distro():
     return (distro_name, distro_version, flavor)
 
 
+@lru_cache()
 def system_info():
     info = {
         'platform': platform.platform(),
@@ -1371,14 +1382,8 @@ def load_file(fname, read_cb=None, quiet=False, decode=True):
         return contents
 
 
-def get_cmdline():
-    if 'DEBUG_PROC_CMDLINE' in os.environ:
-        return os.environ["DEBUG_PROC_CMDLINE"]
-
-    global PROC_CMDLINE
-    if PROC_CMDLINE is not None:
-        return PROC_CMDLINE
-
+@lru_cache()
+def _get_cmdline():
     if is_container():
         try:
             contents = load_file("/proc/1/cmdline")
@@ -1393,10 +1398,16 @@ def get_cmdline():
         except Exception:
             cmdline = ""
 
-    PROC_CMDLINE = cmdline
     return cmdline
 
 
+def get_cmdline():
+    if 'DEBUG_PROC_CMDLINE' in os.environ:
+        return os.environ["DEBUG_PROC_CMDLINE"]
+
+    return _get_cmdline()
+
+
 def pipe_in_out(in_fh, out_fh, chunk_size=1024, chunk_cb=None):
     bytes_piped = 0
     while True:
diff --git a/tests/unittests/test_net.py b/tests/unittests/test_net.py
index 0f45dc38..01119e0a 100644
--- a/tests/unittests/test_net.py
+++ b/tests/unittests/test_net.py
@@ -4576,6 +4576,7 @@ class TestNetRenderers(CiTestCase):
                           priority=['sysconfig', 'eni'])
 
     @mock.patch("cloudinit.net.renderers.netplan.available")
+    @mock.patch("cloudinit.net.renderers.sysconfig.available")
     @mock.patch("cloudinit.net.renderers.sysconfig.available_sysconfig")
     @mock.patch("cloudinit.net.renderers.sysconfig.available_nm")
     @mock.patch("cloudinit.net.renderers.eni.available")
@@ -4583,14 +4584,16 @@ class TestNetRenderers(CiTestCase):
     def test_sysconfig_selected_on_sysconfig_enabled_distros(self, m_distro,
                                                              m_eni, m_sys_nm,
                                                              m_sys_scfg,
+                                                             m_sys_avail,
                                                              m_netplan):
         """sysconfig only selected on specific distros (rhel/sles)."""
 
         # Ubuntu with Network-Manager installed
-        m_eni.return_value = False       # no ifupdown (ifquery)
-        m_sys_scfg.return_value = False  # no sysconfig/ifup/ifdown
-        m_sys_nm.return_value = True     # network-manager is installed
-        m_netplan.return_value = True    # netplan is installed
+        m_eni.return_value = False        # no ifupdown (ifquery)
+        m_sys_scfg.return_value = False   # no sysconfig/ifup/ifdown
+        m_sys_nm.return_value = True      # network-manager is installed
+        m_netplan.return_value = True     # netplan is installed
+        m_sys_avail.return_value = False  # no sysconfig on Ubuntu
         m_distro.return_value = ('ubuntu', None, None)
         self.assertEqual('netplan', renderers.select(priority=None)[0])
 
@@ -4598,7 +4601,8 @@ class TestNetRenderers(CiTestCase):
         m_eni.return_value = False       # no ifupdown (ifquery)
         m_sys_scfg.return_value = False  # no sysconfig/ifup/ifdown
         m_sys_nm.return_value = True     # network-manager is installed
-        m_netplan.return_value = False    # netplan is not installed
+        m_netplan.return_value = False   # netplan is not installed
+        m_sys_avail.return_value = True  # sysconfig is available on centos
         m_distro.return_value = ('centos', None, None)
         self.assertEqual('sysconfig', renderers.select(priority=None)[0])
 
@@ -4606,7 +4610,8 @@ class TestNetRenderers(CiTestCase):
         m_eni.return_value = False       # no ifupdown (ifquery)
         m_sys_scfg.return_value = False  # no sysconfig/ifup/ifdown
         m_sys_nm.return_value = True     # network-manager is installed
-        m_netplan.return_value = False    # netplan is not installed
+        m_netplan.return_value = False   # netplan is not installed
+        m_sys_avail.return_value = True  # sysconfig is available on opensuse
         m_distro.return_value = ('opensuse', None, None)
         self.assertEqual('sysconfig', renderers.select(priority=None)[0])
 
@@ -4625,6 +4630,8 @@ class TestNetRenderers(CiTestCase):
         ]
         for (distro_name, distro_version, flavor) in distro_values:
             m_distro.return_value = (distro_name, distro_version, flavor)
+            if hasattr(util.system_info, "cache_clear"):
+                util.system_info.cache_clear()
             result = sysconfig.available()
             self.assertTrue(result)