Merge lp:~bjornt/charms/trusty/ceph-radosgw/apt-cache-memonly into lp:~openstack-charmers-archive/charms/trusty/ceph-radosgw/trunk

[Björn Tillenius]

Build the Apt cache in memory when checking the ceph version.

This avoids a race condition where something else is rebuilding
the Apt cache in the same directory.

I also changed the imports, so it's clear that it's the apt_pkg
that is being used. There's another module called apt, which
provides a different API, and importing apt_pkg as apt has
fooled me more than once.

Unmerged revisions

=== modified file 'hooks/ceph.py'
--- hooks/ceph.py	2014-01-24 16:04:49 +0000
+++ hooks/ceph.py	2014-07-23 08:51:00 +0000
@@ -11,7 +11,7 @@
 import subprocess
 import time
 import os
-import apt_pkg as apt
+import apt_pkg
 
 from socket import gethostname as get_unit_hostname
 
@@ -223,14 +223,18 @@
 
 
 def get_ceph_version(package=None):
-    apt.init()
-    cache = apt.Cache()
+    apt_pkg.init()
+    # Force Apt to build its cache in memory. That way we avoid race
+    # conditions with other applications building the cache in the same
+    # place.
+    apt_pkg.config.set("Dir::Cache::pkgcache", "")
+    cache = apt_pkg.Cache()
     pkg = cache[package or 'ceph']
     if pkg.current_ver:
-        return apt.upstream_version(pkg.current_ver.ver_str)
+        return apt_pkg.upstream_version(pkg.current_ver.ver_str)
     else:
         return None
 
 
 def version_compare(a, b):
-    return apt.version_compare(a, b)
+    return apt_pkg.version_compare(a, b)