Merge lp:~gandelman-a/charms/precise/keystone/avoid_upgrade_in_install into lp:~openstack-charmers/charms/precise/keystone/ha-support

[Adam Gandelman]

Updates utils.install to check if a package is installed before attempting to install it. This should help avoid unwanted upgrades when re-calling utils.install(*pkgs) from upgrade hooks. Should be merged into the helpers library after here.

[James Page (james-page)]

Works for me

review: Approve

=== modified file 'hooks/lib/utils.py'
--- hooks/lib/utils.py	2013-03-21 18:28:05 +0000
+++ hooks/lib/utils.py	2013-05-03 19:37:23 +0000
@@ -9,6 +9,7 @@
 #  Adam Gandelman <[e-mail]>
 #
 
+import apt_pkg as apt
 import json
 import os
 import subprocess
@@ -29,12 +30,25 @@
 
 
 def install(*pkgs):
+    apt.init()
+    cache = apt.Cache()
+    _pkgs = []
+    # Ensure we only attempt to install packages that are actually needed.
+    for pkg in pkgs:
+        try:
+            p = cache[pkg]
+            p.current_ver or _pkgs.append(pkg)
+        except KeyError:
+            juju_log('ERROR', 'Attempting to install %s but there is no '\
+                     'installation candidate.')
+            sys.exit(1)
+
     cmd = [
         'apt-get',
         '-y',
         'install'
           ]
-    for pkg in pkgs:
+    for pkg in _pkgs:
         cmd.append(pkg)
     subprocess.check_call(cmd)
 
 
=== modified file 'revision'
--- revision	2013-04-25 16:57:49 +0000
+++ revision	2013-05-03 19:37:23 +0000
@@ -1,1 +1,1 @@
-219
+220