Merge lp:~rvb/maas/expose-version-api into lp:~maas-committers/maas/trunk

[Raphaël Badin]

Expose the version and the subversion of the running MAAS on the API.

Note that I'm doing a bit more caching in version.py than would be expected: I want to cache things at the low level so that calls to display the version in the UI and calls to return the version in the API call the API backend only once but I also want to cache the result of the (tiny) processing done by get_maas_version_ui() to avoid doing the string interpolation for every UI page requested.

[Christian Reis (kiko)]

Is there any chance this could be backported to 1.7?

[Blake Rouse (blake-rouse)]

No complaints. Only think the simple_cache decorator would be better in its own file.

review: Approve

[Raphaël Badin (rvb)]

Thanks for the review!

[MAAS Lander (maas-lander)]

The attempt to merge lp:~rvb/maas/expose-version-api into lp:maas failed. Below is the output from the failed tests.

Ign http://security.ubuntu.com trusty-security InRelease
Get:1 http://security.ubuntu.com trusty-security Release.gpg [933 B]
Get:2 http://security.ubuntu.com trusty-security Release [63.5 kB]
Ign http://nova.clouds.archive.ubuntu.com trusty InRelease
Ign http://nova.clouds.archive.ubuntu.com trusty-updates InRelease
Get:3 http://security.ubuntu.com trusty-security/main Sources [76.5 kB]
Hit http://nova.clouds.archive.ubuntu.com trusty Release.gpg
Get:4 http://nova.clouds.archive.ubuntu.com trusty-updates Release.gpg [933 B]
Get:5 http://security.ubuntu.com trusty-security/universe Sources [19.5 kB]
Get:6 http://security.ubuntu.com trusty-security/main amd64 Packages [251 kB]
Hit http://nova.clouds.archive.ubuntu.com trusty Release
Get:7 http://nova.clouds.archive.ubuntu.com trusty-updates Release [63.5 kB]
Get:8 http://security.ubuntu.com trusty-security/universe amd64 Packages [92.0 kB]
Hit http://security.ubuntu.com trusty-security/main Translation-en
Hit http://security.ubuntu.com trusty-security/universe Translation-en
Hit http://nova.clouds.archive.ubuntu.com trusty/main Sources
Hit http://nova.clouds.archive.ubuntu.com trusty/universe Sources
Hit http://nova.clouds.archive.ubuntu.com trusty/main amd64 Packages
Hit http://nova.clouds.archive.ubuntu.com trusty/universe amd64 Packages
Hit http://nova.clouds.archive.ubuntu.com trusty/main Translation-en
Hit http://nova.clouds.archive.ubuntu.com trusty/universe Translation-en
Get:9 http://nova.clouds.archive.ubuntu.com trusty-updates/main Sources [190 kB]
Get:10 http://nova.clouds.archive.ubuntu.com trusty-updates/universe Sources [108 kB]
Get:11 http://nova.clouds.archive.ubuntu.com trusty-updates/main amd64 Packages [490 kB]
Get:12 http://nova.clouds.archive.ubuntu.com trusty-updates/universe amd64 Packages [263 kB]
Hit http://nova.clouds.archive.ubuntu.com trusty-updates/main Translation-en
Hit http://nova.clouds.archive.ubuntu.com trusty-updates/universe Translation-en
Ign http://nova.clouds.archive.ubuntu.com trusty/main Translation-en_US
Ign http://nova.clouds.archive.ubuntu.com trusty/universe Translation-en_US
Fetched 1,621 kB in 3s (526 kB/s)
Reading package lists...
sudo DEBIAN_FRONTEND=noninteractive apt-get -y \
     --no-install-recommends install apache2 authbind bind9 bind9utils build-essential bzr-builddeb chromium-browser chromium-chromedriver curl daemontools debhelper dh-apport dh-systemd distro-info dnsutils firefox freeipmi-tools gjs ipython isc-dhcp-common libjs-angularjs libjs-jquery libjs-jquery-hotkeys libjs-yui3-full libjs-yui3-min libpq-dev make nodejs-legacy npm pep8 postgresql pyflakes python-apt python-bson python-bzrlib python-convoy python-coverage python-crochet python-cssselect python-curtin python-dev python-distro-info python-django python-django-piston python-django-south python-djorm-ext-pgarray python-docutils python-extras python-fixtures python-flake8 python-formencode python-hivex python-httplib2 python-iscpy python-jinja2 python-jsonschema python-lockfile python-lxml python-mock python-netaddr python-netifaces python-nose python-oau...

[MAAS Lander (maas-lander)]

The attempt to merge lp:~rvb/maas/expose-version-api into lp:maas failed. Below is the output from the failed tests.

Ign http://security.ubuntu.com trusty-security InRelease
Hit http://security.ubuntu.com trusty-security Release.gpg
Hit http://security.ubuntu.com trusty-security Release
Ign http://nova.clouds.archive.ubuntu.com trusty InRelease
Ign http://nova.clouds.archive.ubuntu.com trusty-updates InRelease
Hit http://nova.clouds.archive.ubuntu.com trusty Release.gpg
Hit http://nova.clouds.archive.ubuntu.com trusty-updates Release.gpg
Hit http://nova.clouds.archive.ubuntu.com trusty Release
Hit http://nova.clouds.archive.ubuntu.com trusty-updates Release
Hit http://security.ubuntu.com trusty-security/main Sources
Hit http://security.ubuntu.com trusty-security/universe Sources
Hit http://security.ubuntu.com trusty-security/main amd64 Packages
Hit http://nova.clouds.archive.ubuntu.com trusty/main Sources
Hit http://security.ubuntu.com trusty-security/universe amd64 Packages
Hit http://security.ubuntu.com trusty-security/main Translation-en
Hit http://nova.clouds.archive.ubuntu.com trusty/universe Sources
Hit http://security.ubuntu.com trusty-security/universe Translation-en
Hit http://nova.clouds.archive.ubuntu.com trusty/main amd64 Packages
Hit http://nova.clouds.archive.ubuntu.com trusty/universe amd64 Packages
Hit http://nova.clouds.archive.ubuntu.com trusty/main Translation-en
Hit http://nova.clouds.archive.ubuntu.com trusty/universe Translation-en
Hit http://nova.clouds.archive.ubuntu.com trusty-updates/main Sources
Hit http://nova.clouds.archive.ubuntu.com trusty-updates/universe Sources
Hit http://nova.clouds.archive.ubuntu.com trusty-updates/main amd64 Packages
Hit http://nova.clouds.archive.ubuntu.com trusty-updates/universe amd64 Packages
Hit http://nova.clouds.archive.ubuntu.com trusty-updates/main Translation-en
Hit http://nova.clouds.archive.ubuntu.com trusty-updates/universe Translation-en
Ign http://nova.clouds.archive.ubuntu.com trusty/main Translation-en_US
Ign http://nova.clouds.archive.ubuntu.com trusty/universe Translation-en_US
Reading package lists...
sudo DEBIAN_FRONTEND=noninteractive apt-get -y \
     --no-install-recommends install apache2 authbind bind9 bind9utils build-essential bzr-builddeb chromium-browser chromium-chromedriver curl daemontools debhelper dh-apport dh-systemd distro-info dnsutils firefox freeipmi-tools gjs ipython isc-dhcp-common libjs-angularjs libjs-jquery libjs-jquery-hotkeys libjs-yui3-full libjs-yui3-min libpq-dev make nodejs-legacy npm pep8 postgresql pyflakes python-apt python-bson python-bzrlib python-convoy python-coverage python-crochet python-cssselect python-curtin python-dev python-distro-info python-django python-django-piston python-django-south python-djorm-ext-pgarray python-docutils python-extras python-fixtures python-flake8 python-formencode python-hivex python-httplib2 python-iscpy python-jinja2 python-jsonschema python-lockfile python-lxml python-mock python-netaddr python-netifaces python-nose python-oauth python-openssl python-paramiko python-pexpect python-pip python-pocket-lint python-psycopg2 python-pyinotify python-pyparsing python-seamicroclient python-simplejson pyt...

[MAAS Lander (maas-lander)]

The attempt to merge lp:~rvb/maas/expose-version-api into lp:maas failed. Below is the output from the failed tests.

Ign http://security.ubuntu.com trusty-security InRelease
Get:1 http://security.ubuntu.com trusty-security Release.gpg [933 B]
Get:2 http://security.ubuntu.com trusty-security Release [63.5 kB]
Ign http://nova.clouds.archive.ubuntu.com trusty InRelease
Ign http://nova.clouds.archive.ubuntu.com trusty-updates InRelease
Hit http://nova.clouds.archive.ubuntu.com trusty Release.gpg
Get:3 http://nova.clouds.archive.ubuntu.com trusty-updates Release.gpg [933 B]
Hit http://nova.clouds.archive.ubuntu.com trusty Release
Get:4 http://nova.clouds.archive.ubuntu.com trusty-updates Release [63.5 kB]
Get:5 http://security.ubuntu.com trusty-security/main Sources [76.4 kB]
Hit http://nova.clouds.archive.ubuntu.com trusty/main Sources
Get:6 http://security.ubuntu.com trusty-security/universe Sources [19.5 kB]
Get:7 http://security.ubuntu.com trusty-security/main amd64 Packages [252 kB]
Hit http://nova.clouds.archive.ubuntu.com trusty/universe Sources
Hit http://nova.clouds.archive.ubuntu.com trusty/main amd64 Packages
Hit http://nova.clouds.archive.ubuntu.com trusty/universe amd64 Packages
Hit http://nova.clouds.archive.ubuntu.com trusty/main Translation-en
Hit http://nova.clouds.archive.ubuntu.com trusty/universe Translation-en
Get:8 http://nova.clouds.archive.ubuntu.com trusty-updates/main Sources [190 kB]
Get:9 http://security.ubuntu.com trusty-security/universe amd64 Packages [92.0 kB]
Hit http://security.ubuntu.com trusty-security/main Translation-en
Hit http://security.ubuntu.com trusty-security/universe Translation-en
Get:10 http://nova.clouds.archive.ubuntu.com trusty-updates/universe Sources [108 kB]
Get:11 http://nova.clouds.archive.ubuntu.com trusty-updates/main amd64 Packages [490 kB]
Get:12 http://nova.clouds.archive.ubuntu.com trusty-updates/universe amd64 Packages [263 kB]
Hit http://nova.clouds.archive.ubuntu.com trusty-updates/main Translation-en
Hit http://nova.clouds.archive.ubuntu.com trusty-updates/universe Translation-en
Ign http://nova.clouds.archive.ubuntu.com trusty/main Translation-en_US
Ign http://nova.clouds.archive.ubuntu.com trusty/universe Translation-en_US
Fetched 1,621 kB in 3s (524 kB/s)
Reading package lists...
sudo DEBIAN_FRONTEND=noninteractive apt-get -y \
     --no-install-recommends install apache2 authbind bind9 bind9utils build-essential bzr-builddeb chromium-browser chromium-chromedriver curl daemontools debhelper dh-apport dh-systemd distro-info dnsutils firefox freeipmi-tools gjs ipython isc-dhcp-common libjs-angularjs libjs-jquery libjs-jquery-hotkeys libjs-yui3-full libjs-yui3-min libpq-dev make nodejs-legacy npm pep8 postgresql pyflakes python-apt python-bson python-bzrlib python-convoy python-coverage python-crochet python-cssselect python-curtin python-dev python-distro-info python-django python-django-piston python-django-south python-djorm-ext-pgarray python-docutils python-extras python-fixtures python-flake8 python-formencode python-hivex python-httplib2 python-iscpy python-jinja2 python-jsonschema python-lockfile python-lxml python-mock python-netaddr python-netifaces python-nose python-oau...

[MAAS Lander (maas-lander)]

There are additional revisions which have not been approved in review. Please seek review and approval of these new revisions.

[Gavin Panella (allenap)]

Not a review, but a few comments (and one in the diff):

* Is "subversion" the best term. People often talk about major and minor
  versions.

* The distutils.version module might be of interest.

* One of the explicit reasons for the capabilities views was to
  *discourage* use of version numbers when testing for features. Is this
  therefore a regression? What's the use case?

[Raphaël Badin (rvb)]

Hey Gavin

> Not a review, but a few comments (and one in the diff):

> * Is "subversion" the best term. People often talk about major and minor
> versions.

AFAIK, major and minor are used for something different: "1.8.0" → major: 1, minor: 8. Here we really want version/subversion I think.

> * One of the explicit reasons for the capabilities views was to
> *discourage* use of version numbers when testing for features. Is this
> therefore a regression? What's the use case?

The capabilities are the thing other tools like Juju should use to check for functionality but some times it's useful (mostly when debugging) to be able to know exactly what the version is in order to, say, figure out if a particular bug fix is present.

=== modified file 'src/maasserver/api/tests/test_version.py'
--- src/maasserver/api/tests/test_version.py	2014-08-18 13:23:21 +0000
+++ src/maasserver/api/tests/test_version.py	2015-04-08 15:11:40 +0000
@@ -21,6 +21,7 @@
 from django.core.urlresolvers import reverse
 from maasserver.api.version import API_CAPABILITIES_LIST
 from maasserver.testing.testcase import MAASServerTestCase
+from maasserver.utils import version as version_module
 
 
 class TestFindingResources(MAASServerTestCase):
@@ -31,6 +32,10 @@
             '/api/1.0/version/', reverse('version'))
 
     def test_GET_returns_details(self):
+        mock_apt = self.patch(version_module, "get_version_from_apt")
+        mock_apt.return_value = "1.8.0~alpha4+bzr356-0ubuntu1"
+        self.patch(version_module, "_cache", {})
+
         response = self.client.get(reverse('version'))
         self.assertEqual(httplib.OK, response.status_code)
 
@@ -38,5 +43,7 @@
         self.assertEqual(
             {
                 'capabilities': API_CAPABILITIES_LIST,
+                'version': '1.8.0',
+                'subversion': 'alpha4+bzr356',
             },
             parsed_result)

=== modified file 'src/maasserver/api/version.py'
--- src/maasserver/api/version.py	2014-09-17 02:17:35 +0000
+++ src/maasserver/api/version.py	2015-04-08 15:11:40 +0000
@@ -20,6 +20,7 @@
 
 from django.http import HttpResponse
 from maasserver.api.support import AnonymousOperationsHandler
+from maasserver.utils.version import get_maas_version_subversion
 
 # MAAS capabilities. See docs/capabilities.rst for documentation.
 CAP_NETWORKS_MANAGEMENT = 'networks-management'
@@ -39,6 +40,8 @@
     This returns a JSON dictionary with information about this
     MAAS instance.
     {
+        'version': '1.8.0',
+        'subversion': 'alpha10+bzr3750',
         'capabilities': ['capability1', 'capability2', ...]
     }
     """
@@ -46,8 +49,12 @@
     create = update = delete = None
 
     def read(self, request):
+        version, subversion = get_maas_version_subversion()
         version_info = {
             'capabilities': API_CAPABILITIES_LIST,
+            'version': version,
+            'subversion': subversion,
+
         }
         return HttpResponse(
             version_info, mimetype='application/json; charset=utf-8',

=== modified file 'src/maasserver/context_processors.py'
--- src/maasserver/context_processors.py	2015-04-02 14:18:18 +0000
+++ src/maasserver/context_processors.py	2015-04-08 15:11:40 +0000
@@ -23,7 +23,7 @@
 from maasserver.models import Config
 from maasserver.utils.version import (
     get_maas_doc_version,
-    get_maas_version,
+    get_maas_version_ui,
 )
 
 
@@ -88,6 +88,6 @@
             'site_name': Config.objects.get_config('maas_name'),
         },
         'debug': settings.DEBUG,
-        'version': get_maas_version(),
+        'version': get_maas_version_ui(),
         'doc_version': get_maas_doc_version(),
     }

=== modified file 'src/maasserver/utils/tests/test_version.py'
--- src/maasserver/utils/tests/test_version.py	2015-03-30 19:38:57 +0000
+++ src/maasserver/utils/tests/test_version.py	2015-04-08 15:11:40 +0000
@@ -63,64 +63,6 @@
             version.get_version_from_apt(version.REGION_PACKAGE_NAME))
 
 
-class TestFormatVersion(MAASTestCase):
-
-    scenarios = [
-        ("with ~", {
-            "version": "1.8.0~alpha4+bzr356-0ubuntu1",
-            "output": "1.8.0 (alpha4+bzr356)",
-            }),
-        ("without ~", {
-            "version": "1.8.0+bzr356-0ubuntu1",
-            "output": "1.8.0 (+bzr356)",
-            }),
-        ("without ~ or +", {
-            "version": "1.8.0-0ubuntu1",
-            "output": "1.8.0",
-            }),
-    ]
-
-    def test__returns_formatted_version(self):
-        self.assertEquals(self.output, version.format_version(self.version))
-
-
-class TestGetMAASRegionPackageVersion(MAASTestCase):
-
-    def test__returns_value_from_global(self):
-        self.patch(version, "MAAS_VERSION", sentinel.maas_version)
-        self.assertIs(
-            sentinel.maas_version, version.get_maas_region_package_version())
-
-    def test__calls_get_version_from_apt_if_global_not_set(self):
-        self.patch(version, "MAAS_VERSION", None)
-        mock_apt = self.patch(version, "get_version_from_apt")
-        version.get_maas_region_package_version()
-        self.assertThat(
-            mock_apt, MockCalledOnceWith(version.REGION_PACKAGE_NAME))
-
-    def test__calls_format_version_with_version_from_apt(self):
-        self.patch(version, "MAAS_VERSION", None)
-        current_ver = "1.8.0~alpha4+bzr356-0ubuntu1"
-        mock_apt = self.patch(version, "get_version_from_apt")
-        mock_apt.return_value = current_ver
-        mock_format = self.patch(version, "format_version")
-        mock_format.return_value = sentinel.format
-        self.expectThat(
-            version.get_maas_region_package_version(), Is(sentinel.format))
-        self.expectThat(
-            mock_format, MockCalledOnceWith(current_ver))
-
-    def test__sets_global_value(self):
-        self.patch(version, "MAAS_VERSION", None)
-        current_ver = "1.8.0~alpha4+bzr356-0ubuntu1"
-        mock_apt = self.patch(version, "get_version_from_apt")
-        mock_apt.return_value = current_ver
-        mock_format = self.patch(version, "format_version")
-        mock_format.return_value = sentinel.format
-        version.get_maas_region_package_version()
-        self.assertIs(sentinel.format, version.MAAS_VERSION)
-
-
 class TestGetMAASBranch(MAASTestCase):
 
     def test__returns_None_if_Branch_is_None(self):
@@ -139,61 +81,137 @@
         self.assertIsNone(version.get_maas_branch())
 
 
-class TestGetMAASVersion(MAASTestCase):
-
-    def test__returns_version_from_get_maas_region_package_version(self):
-        mock_version = self.patch(version, "get_maas_region_package_version")
-        mock_version.return_value = sentinel.version
-        self.assertIs(sentinel.version, version.get_maas_version())
-
-    def test__returns_unknown_if_version_is_empty_and_not_bzr_branch(self):
-        mock_version = self.patch(version, "get_maas_region_package_version")
-        mock_version.return_value = ""
-        mock_branch = self.patch(version, "get_maas_branch")
-        mock_branch.return_value = None
-        self.assertEquals("unknown", version.get_maas_version())
-
-    def test__returns_from_source_and_revno_from_branch(self):
-        mock_version = self.patch(version, "get_maas_region_package_version")
-        mock_version.return_value = ""
-        revno = random.randint(1, 5000)
-        mock_branch = self.patch(version, "get_maas_branch")
-        mock_branch.return_value.revno.return_value = revno
-        self.assertEquals(
-            "from source (+bzr%s)" % revno, version.get_maas_version())
-
-
-class TestGetMAASMainVersion(MAASTestCase):
-
-    def test__returns_main_version_from_package_version_with_space(self):
-        mock_version = self.patch(version, "get_maas_region_package_version")
-        mock_version.return_value = "1.8.0 (alpha4+bzr356)"
-        self.assertEquals("1.8.0", version.get_maas_main_version())
-
-    def test__returns_main_version_from_package_version_without_space(self):
-        mock_version = self.patch(version, "get_maas_region_package_version")
-        mock_version.return_value = "1.8.0"
-        self.assertEquals("1.8.0", version.get_maas_main_version())
-
-    def test__returns_empty_if_version_is_empty(self):
-        mock_version = self.patch(version, "get_maas_region_package_version")
-        mock_version.return_value = ""
-        self.assertEquals("", version.get_maas_main_version())
-
-
-class TestGetMAASDocVersion(MAASTestCase):
+class TestExtractVersionSubversion(MAASTestCase):
+
+    scenarios = [
+        ("with ~", {
+            "version": "1.8.0~alpha4+bzr356-0ubuntu1",
+            "output": ("1.8.0", "alpha4+bzr356"),
+            }),
+        ("without ~", {
+            "version": "1.8.0+bzr356-0ubuntu1",
+            "output": ("1.8.0", "+bzr356"),
+            }),
+        ("without ~ or +", {
+            "version": "1.8.0-0ubuntu1",
+            "output": ("1.8.0", ""),
+            }),
+    ]
+
+    def test__returns_version_subversion(self):
+        self.assertEquals(
+            self.output, version.extract_version_subversion(self.version))
+
+
+class TestVersionTestCase(MAASTestCase):
+    """MAASTestCase that resets the cache used by utility methods."""
+
+    def setUp(self):
+        super(TestVersionTestCase, self).setUp()
+        self.patch(version, "_cache", {})
+
+
+class TestGetMAASPackageVersion(TestVersionTestCase):
+
+    def test__calls_get_version_from_apt(self):
+        mock_apt = self.patch(version, "get_version_from_apt")
+        mock_apt.return_value = sentinel.version
+        self.expectThat(
+            version.get_maas_package_version(), Is(sentinel.version))
+        self.expectThat(
+            mock_apt, MockCalledOnceWith(version.REGION_PACKAGE_NAME))
+
+
+class TestGetMAASVersionSubversion(TestVersionTestCase):
+
+    def test__returns_package_version(self):
+        mock_apt = self.patch(version, "get_version_from_apt")
+        mock_apt.return_value = "1.8.0~alpha4+bzr356-0ubuntu1"
+        self.assertEquals(
+            ("1.8.0", "alpha4+bzr356"), version.get_maas_version_subversion())
+
+    def test__returns_unknown_if_version_is_empty_and_not_bzr_branch(self):
+        mock_version = self.patch(version, "get_version_from_apt")
+        mock_version.return_value = ""
+        mock_branch = self.patch(version, "get_maas_branch")
+        mock_branch.return_value = None
+        self.assertEquals(
+            ("unknown", ""), version.get_maas_version_subversion())
+
+    def test__returns_from_source_and_revno_from_branch(self):
+        mock_version = self.patch(version, "get_version_from_apt")
+        mock_version.return_value = ""
+        revno = random.randint(1, 5000)
+        mock_branch = self.patch(version, "get_maas_branch")
+        mock_branch.return_value.revno.return_value = revno
+        self.assertEquals(
+            ("from source (+bzr%s)" % revno, ""),
+            version.get_maas_version_subversion())
+
+
+class TestGetMAASVersionUI(TestVersionTestCase):
+
+    def test__returns_package_version(self):
+        mock_apt = self.patch(version, "get_version_from_apt")
+        mock_apt.return_value = "1.8.0~alpha4+bzr356-0ubuntu1"
+        self.assertEquals(
+            "1.8.0 (alpha4+bzr356)", version.get_maas_version_ui())
+
+    def test__returns_unknown_if_version_is_empty_and_not_bzr_branch(self):
+        mock_version = self.patch(version, "get_version_from_apt")
+        mock_version.return_value = ""
+        mock_branch = self.patch(version, "get_maas_branch")
+        mock_branch.return_value = None
+        self.assertEquals("unknown", version.get_maas_version_ui())
+
+    def test__returns_from_source_and_revno_from_branch(self):
+        mock_version = self.patch(version, "get_version_from_apt")
+        mock_version.return_value = ""
+        revno = random.randint(1, 5000)
+        mock_branch = self.patch(version, "get_maas_branch")
+        mock_branch.return_value.revno.return_value = revno
+        self.assertEquals(
+            "from source (+bzr%s)" % revno, version.get_maas_version_ui())
+
+
+class TestGetMAASDocVersion(TestVersionTestCase):
 
     def test__returns_doc_version_with_greater_than_1_decimals(self):
-        mock_version = self.patch(version, "get_maas_main_version")
-        mock_version.return_value = "1.8.0"
+        mock_apt = self.patch(version, "get_version_from_apt")
+        mock_apt.return_value = "1.8.0~alpha4+bzr356-0ubuntu1"
         self.assertEquals("docs1.8", version.get_maas_doc_version())
 
     def test__returns_doc_version_with_equal_to_1_decimals(self):
-        mock_version = self.patch(version, "get_maas_main_version")
-        mock_version.return_value = "1.8"
+        mock_apt = self.patch(version, "get_version_from_apt")
+        mock_apt.return_value = "1.8~alpha4+bzr356-0ubuntu1"
         self.assertEquals("docs1.8", version.get_maas_doc_version())
 
     def test__returns_just_doc_if_version_is_empty(self):
-        mock_version = self.patch(version, "get_maas_main_version")
-        mock_version.return_value = ""
+        mock_apt = self.patch(version, "get_version_from_apt")
+        mock_apt.return_value = ""
         self.assertEquals("docs", version.get_maas_doc_version())
+
+
+class TestVersionMethodsCached(TestVersionTestCase):
+
+    scenarios = [
+        ("get_maas_package_version", dict(method="get_maas_package_version")),
+        ("get_maas_version_subversion", dict(
+            method="get_maas_version_subversion")),
+        ("get_maas_version_ui", dict(method="get_maas_version_ui")),
+        ("get_maas_doc_version", dict(method="get_maas_doc_version")),
+        ]
+
+    def test_method_is_cached(self):
+        mock_apt = self.patch(version, "get_version_from_apt")
+        mock_apt.return_value = "1.8.0~alpha4+bzr356-0ubuntu1"
+        cached_method = getattr(version, self.method)
+        first_return_value = cached_method()
+        second_return_value = cached_method()
+        # The return value is not empty (full unit tests have been performed
+        # earlier).
+        self.assertNotIn(first_return_value, [b'', u'', None])
+        self.assertEqual(first_return_value, second_return_value)
+        # Apt has only been called once.
+        self.expectThat(
+            mock_apt, MockCalledOnceWith(version.REGION_PACKAGE_NAME))

=== modified file 'src/maasserver/utils/version.py'
--- src/maasserver/utils/version.py	2015-03-30 17:54:35 +0000
+++ src/maasserver/utils/version.py	2015-04-08 15:11:40 +0000
@@ -14,7 +14,8 @@
 __metaclass__ = type
 __all__ = [
     "get_maas_doc_version",
-    "get_maas_version",
+    "get_maas_version_subversion",
+    "get_maas_version_ui",
     ]
 
 import apt_pkg
@@ -29,9 +30,6 @@
 # Initialize apt_pkg.
 apt_pkg.init()
 
-# Holds the version of maas.
-MAAS_VERSION = None
-
 # Name of maas package to get version from.
 REGION_PACKAGE_NAME = "maas-region-controller-min"
 
@@ -50,34 +48,16 @@
         return ""
 
 
-def format_version(version):
-    """Format `version` into a better looking string for the UI."""
+def extract_version_subversion(version):
+    """Return a tuple (version, subversion) from the given apt version."""
     if "~" in version:
         main_version, extra = version.split("~", 1)
-        return "%s (%s)" % (main_version, extra.split("-", 1)[0])
+        return main_version, extra.split("-", 1)[0]
     elif "+" in version:
         main_version, extra = version.split("+", 1)
-        return "%s (+%s)" % (main_version, extra.split("-", 1)[0])
+        return main_version, "+" + extra.split("-", 1)[0]
     else:
-        return version.split("-", 1)[0]
-
-
-def get_maas_region_package_version():
-    """Return the dpkg version for `REGION_PACKAGE_NAME`.
-
-    Lazy loads the version. Once loaded it will not be loaded again.
-    This is to speed up the call to this method and also to require the
-    region to be restarted to see the new version.
-    """
-    global MAAS_VERSION
-    if MAAS_VERSION is None:
-        MAAS_VERSION = get_version_from_apt(REGION_PACKAGE_NAME)
-        # Possibly this returned an empty string, meaning it's not installed
-        # and no need to call again.
-        if MAAS_VERSION:
-            # It is a valid version so set the correct format.
-            MAAS_VERSION = format_version(MAAS_VERSION)
-    return MAAS_VERSION
+        return version.split("-", 1)[0], ''
 
 
 def get_maas_branch():
@@ -90,41 +70,62 @@
         return None
 
 
-def get_maas_version():
-    """Return the version string for the running MAAS region."""
-    # MAAS is installed from package, return the version string.
-    version = get_maas_region_package_version()
-    if version:
-        return version
+_cache = {}
+
+
+# A very simply memoize function: when we switch to Django 1.7 we should use
+# Django's lru_cache method.
+def simple_cache(fun):
+    def wrapped(*args, **kwargs):
+        key = hash(repr(fun) + repr(args) + repr(kwargs))
+        if not key in _cache:
+            _cache[key] = fun(*args, **kwargs)
+        return _cache[key]
+
+    wrapped.__doc__ = "%s %s" % (fun.__doc__, "(cached)")
+    return wrapped
+
+
+@simple_cache
+def get_maas_package_version():
+    """Return the apt version for the main MAAS package."""
+    return get_version_from_apt(REGION_PACKAGE_NAME)
+
+
+@simple_cache
+def get_maas_version_subversion():
+    """Return a tuple with the MAAS version and the MAAS subversion."""
+    apt_version = get_maas_package_version()
+    if apt_version:
+        return extract_version_subversion(apt_version)
     else:
         # Get the branch information
         branch = get_maas_branch()
         if branch is None:
             # Not installed not in branch, then no way to identify. This should
             # not happen, but just in case.
-            return "unknown"
-        else:
-            return "from source (+bzr%s)" % branch.revno()
-
-
-def get_maas_main_version():
-    """Return the main version for the running MAAS region."""
-    # MAAS is installed from package, return the version string.
-    version = get_maas_region_package_version()
-    if version:
-        if " " in version:
-            return version.split(" ")[0]
-        else:
-            return version
-    else:
-        return ""
-
-
+            return "unknown", ''
+        else:
+            return "from source (+bzr%s)" % branch.revno(), ''
+
+
+@simple_cache
+def get_maas_version_ui():
+    """Return the version string for the running MAAS region.
+
+    The returned string is suitable to display in the UI.
+    """
+    version, subversion = get_maas_version_subversion()
+    return "%s (%s)" % (version, subversion) if subversion else version
+
+
+@simple_cache
 def get_maas_doc_version():
     """Return the doc version for the running MAAS region."""
-    main_version = get_maas_main_version()
     doc_prefix = 'docs'
-    if not main_version:
+    apt_version = get_maas_package_version()
+    if apt_version:
+        version, _ = extract_version_subversion(apt_version)
+        return doc_prefix + '.'.join(version.split('.')[:2])
+    else:
         return doc_prefix
-    else:
-        return doc_prefix + '.'.join(main_version.split('.')[:2])