Merge lp:~stub/charm-helpers/meminfo into lp:charm-helpers

[Stuart Bishop]

Helper to get the total system RAM.

This helper keeps getting reimplemented, so lets stick it in charm-helpers and stop wasting time.

[lp:~stub/charm-helpers/meminfo]

417. By Stuart Bishop on 2015-07-28

Test filename and mode too

[Stuart Bishop (stub)]

I'm going to land this if there are no objections.

=== modified file 'charmhelpers/core/host.py'
--- charmhelpers/core/host.py	2015-07-15 16:36:29 +0000
+++ charmhelpers/core/host.py	2015-07-28 04:07:46 +0000
@@ -492,3 +492,19 @@
 
 def lchownr(path, owner, group):
     chownr(path, owner, group, follow_links=False)
+
+
+def get_total_ram():
+    '''The total amount of system RAM in bytes.
+
+    This is what is reported by the OS, and may be overcommitted when
+    there are multiple containers hosted on the same machine.
+    '''
+    with open('/proc/meminfo', 'r') as f:
+        for line in f.readlines():
+            if line:
+                key, value, unit = line.split()
+                if key == 'MemTotal:':
+                    assert unit == 'kB', 'Unknown unit'
+                    return int(value) * 1024  # Classic, not KiB.
+        raise NotImplementedError()

=== modified file 'tests/core/test_host.py'
--- tests/core/test_host.py	2015-07-15 15:46:23 +0000
+++ tests/core/test_host.py	2015-07-28 04:07:46 +0000
@@ -3,6 +3,7 @@
 import subprocess
 from tempfile import mkdtemp
 from shutil import rmtree
+from textwrap import dedent
 
 import apt_pkg
 
@@ -1005,3 +1006,14 @@
         self.assertEqual(host.cmp_pkgrevno('python', '2.3'), 1)
         self.assertEqual(host.cmp_pkgrevno('python', '2.4'), 0)
         self.assertEqual(host.cmp_pkgrevno('python', '2.5'), -1)
+
+    def test_get_total_ram(self):
+        raw = dedent('''\
+                     MemFree:          183868 kB
+                     MemTotal:        7096108 kB
+                     MemAvailable:    5645240 kB
+                     ''').strip()
+        with patch_open() as (mock_open, mock_file):
+            mock_file.readlines.return_value = raw.splitlines()
+            self.assertEqual(host.get_total_ram(), 7266414592)  # 7GB
+            mock_open.assert_called_once_with('/proc/meminfo', 'r')