Merge lp:~frankban/juju-quickstart/envs-backup into lp:juju-quickstart

[Francesco Banconi]

Create a backup copy of the envs file.

In a pre-imp call with Gary, we decided the
following strategy: a backup copy of the
environments.yaml file is created once per
quickstart session the first time environments
are changed by the user. This way we prevent the
original backup to be overwritten if the user
makes two subsequent changes to the envs.

Tests: `make check`.

QA:

- Create a backup copy of your environments file:
  `cp ~/.juju/environments.yaml ~/environments.yaml.bak`.

- Run `.venv/bin/python juju-quickstart -i`, select one
  of your environments, exit with ^X without changing anything.
  Check your original file has not been changed.

- Run `.venv/bin/python juju-quickstart -i`, change something
  (e.g. create, remove or change an environment, or just change
  the default one). Change at least two environments.
  Exit with ^X. The envs.yaml file now should be the one
  generated by quickstart and should reflect your changes.
  It also includes the path to the backup copy, which
  should be your original file.

- Restore your original environments file:
  `mv ~/environments.yaml.bak ~/.juju/environments.yaml`.

Done, thank you!

https://codereview.appspot.com/51520043/

[Francesco Banconi (frankban)]

Reviewers: mp+201449_code.launchpad.net,

Message:
Please take a look.

Description:
Create a backup copy of the envs file.

In a pre-imp call with Gary, we decided the
following strategy: a backup copy of the
environments.yaml file is created once per
quickstart session the first time environments
are changed by the user. This way we prevent the
original backup to be overwritten if the user
makes two subsequent changes to the envs.

Tests: `make check`.

QA:

- Create a backup copy of your environments file:
   `cp ~/.juju/environments.yaml ~/environments.yaml.bak`.

- Run `.venv/bin/python juju-quickstart -i`, select one
   of your environments, exit with ^X without changing anything.
   Check your original file has not been changed.

- Run `.venv/bin/python juju-quickstart -i`, change something
   (e.g. create, remove or change an environment, or just change
   the default one). Change at least two environments.
   Exit with ^X. The envs.yaml file now should be the one
   generated by quickstart and should reflect your changes.
   It also includes the path to the backup copy, which
   should be your original file.

- Restore your original environments file:
   `mv ~/environments.yaml.bak ~/.juju/environments.yaml`.

Done, thank you!

https://code.launchpad.net/~frankban/juju-quickstart/envs-backup/+merge/201449

(do not edit description out of merge proposal)

Please review this at https://codereview.appspot.com/51520043/

Affected files (+116, -9 lines):
   A [revision details]
   M quickstart/manage.py
   M quickstart/models/envs.py
   M quickstart/tests/models/test_envs.py
   M quickstart/tests/test_manage.py
   M quickstart/tests/test_utils.py
   M quickstart/utils.py

[lp:~frankban/juju-quickstart/envs-backup]

61. By Francesco Banconi on 2014-01-13

Fix typo.

[Francesco Banconi (frankban)]

Matthew approved this MP, but he's not currently able to log in to
Rietveld.
Thanks for the review, submitting now.

https://codereview.appspot.com/51520043/

[Francesco Banconi (frankban)]

*** Submitted:

Create a backup copy of the envs file.

In a pre-imp call with Gary, we decided the
following strategy: a backup copy of the
environments.yaml file is created once per
quickstart session the first time environments
are changed by the user. This way we prevent the
original backup to be overwritten if the user
makes two subsequent changes to the envs.

Tests: `make check`.

QA:

- Create a backup copy of your environments file:
   `cp ~/.juju/environments.yaml ~/environments.yaml.bak`.

- Run `.venv/bin/python juju-quickstart -i`, select one
   of your environments, exit with ^X without changing anything.
   Check your original file has not been changed.

- Run `.venv/bin/python juju-quickstart -i`, change something
   (e.g. create, remove or change an environment, or just change
   the default one). Change at least two environments.
   Exit with ^X. The envs.yaml file now should be the one
   generated by quickstart and should reflect your changes.
   It also includes the path to the backup copy, which
   should be your original file.

- Restore your original environments file:
   `mv ~/environments.yaml.bak ~/.juju/environments.yaml`.

Done, thank you!

R=
CC=
https://codereview.appspot.com/51520043

https://codereview.appspot.com/51520043/

=== modified file 'quickstart/manage.py'
--- quickstart/manage.py	2014-01-13 15:30:44 +0000
+++ quickstart/manage.py	2014-01-13 16:51:49 +0000
@@ -25,6 +25,7 @@
 import codecs
 import logging
 import os
+import shutil
 import sys
 import webbrowser
 
@@ -155,9 +156,11 @@
     application with an error if an OSError exception is raised while saving
     the environments database.
     """
+    backup_function = utils.run_once(shutil.copyfile)
+
     def save_callable(env_db):
         try:
-            envs.save(env_file, env_db)
+            envs.save(env_file, env_db, backup_function=backup_function)
         except OSError as err:
             return parser.error(bytes(err))
 
 
=== modified file 'quickstart/models/envs.py'
--- quickstart/models/envs.py	2014-01-10 09:08:06 +0000
+++ quickstart/models/envs.py	2014-01-13 16:51:49 +0000
@@ -190,24 +190,38 @@
     return env_db
 
 
-def save(env_file, env_db):
+def save(env_file, env_db, backup_function=None):
     """Save the given env_db to the provided environments.yaml file.
 
     The new environments are saved to disk in the most atomic way possible.
+    If backup_function is not None, it is called passing the original
+    environments file path and the backup destination path. The backup is
+    obviously performed only if the file exists.
 
     Raise an OSError if any errors occur in the process.
     """
+    dirname = os.path.dirname(env_file)
+    backup_file = None
+    if os.path.exists(env_file):
+        if backup_function is not None:
+            # Create a backup of the original file.
+            backup_file = env_file + '.quickstart.bak'
+            backup_function(env_file, backup_file)
+    else:
+        utils.mkdir(dirname)
+    banner = utils.get_quickstart_banner()
     # Save the contents in a temporary file, then rename to the real file.
     # Since the renaming operation may fail on some Unix flavors if the source
     # and destination files are on different file systems, use for the
     # temporary file the same directory where the env_file is stored.
-    dirname = os.path.dirname(env_file)
-    utils.mkdir(dirname)
-    banner = utils.get_quickstart_banner()
     try:
         temp_file = tempfile.NamedTemporaryFile(
             prefix='quickstart-temp-envs-', dir=dirname, delete=False)
         temp_file.write(banner.encode('utf-8'))
+        if backup_file is not None:
+            temp_file.write(
+                '# A backup copy of this file can be found in\n'
+                '# {}\n\n'.format(backup_file))
         serializers.yaml_dump(env_db, temp_file)
     except Exception as err:
         raise OSError(err)
 
=== modified file 'quickstart/tests/models/test_envs.py'
--- quickstart/tests/models/test_envs.py	2014-01-09 12:48:20 +0000
+++ quickstart/tests/models/test_envs.py	2014-01-13 16:51:49 +0000
@@ -22,6 +22,8 @@
 import copy
 import functools
 import os
+import shutil
+import tempfile
 import unittest
 
 import mock
@@ -199,6 +201,18 @@
         self.env_file = self.make_env_file()
         self.original_contents = open(self.env_file).read()
 
+    def make_juju_home(self):
+        """Create a temporary Juju home directory.
+
+        Return the Juju home path and the path of the corresponding
+        environments file.
+        """
+        playground = tempfile.mkdtemp()
+        self.addCleanup(shutil.rmtree, playground)
+        juju_home = os.path.join(playground, '.juju')
+        os.mkdir(juju_home)
+        return juju_home, os.path.join(juju_home, 'environments.yaml')
+
     def test_dump_error(self):
         # An OSError is raised if errors occur in the serialization process.
         with mock.patch('quickstart.serializers.yaml_dump') as mock_yaml_dump:
@@ -238,6 +252,37 @@
         # Also the new contents have been saved.
         self.assertIn('new: contents', contents)
 
+    def test_backup(self):
+        # A backup function, if provided, is used to create a backup copy
+        # of the original environments file.
+        mock_backup = mock.Mock()
+        envs.save(
+            self.env_file, {'new': 'contents'}, backup_function=mock_backup)
+        contents = open(self.env_file).read()
+        expected_backup_path = self.env_file + '.quickstart.bak'
+        # The backup function has been called.
+        mock_backup.assert_called_once_with(
+            self.env_file, expected_backup_path)
+        # The new file indicates where to find the backup copy.
+        self.assertIn(
+            '# A backup copy of this file can be found in\n'
+            '# {}\n'.format(expected_backup_path),
+            contents)
+
+    def test_missing_juju_home(self):
+        # The environments file directory is created if not existing.
+        juju_home, env_file = self.make_juju_home()
+        shutil.rmtree(juju_home)
+        envs.save(env_file, {'new': 'contents'})
+        self.assertTrue(os.path.isdir(juju_home))
+
+    def test_backup_missing_juju_home(self):
+        # The backup function is not executed if there is nothing to backup.
+        juju_home, env_file = self.make_juju_home()
+        mock_backup = mock.Mock()
+        envs.save(env_file, {'new': 'contents'}, backup_function=mock_backup)
+        self.assertFalse(mock_backup.called)
+
 
 class EnvDataTestsMixin(object):
     """Set up an initial environments dictionary."""
 
=== modified file 'quickstart/tests/test_manage.py'
--- quickstart/tests/test_manage.py	2014-01-13 15:30:44 +0000
+++ quickstart/tests/test_manage.py	2014-01-13 16:51:49 +0000
@@ -278,13 +278,16 @@
         self.parser = mock.Mock()
         self.env_file = '/tmp/envfile.yaml'
         self.env_db = helpers.make_env_db()
-        self.save_callable = manage._create_save_callable(
-            self.parser, self.env_file)
+        with mock.patch('quickstart.manage.utils.run_once') as mock_run_once:
+            self.save_callable = manage._create_save_callable(
+                self.parser, self.env_file)
+        self.mock_run_once = mock_run_once
 
     def test_saved(self, mock_save):
         # The returned function correctly saves the new environments database.
         self.save_callable(self.env_db)
-        mock_save.assert_called_once_with(self.env_file, self.env_db)
+        mock_save.assert_called_once_with(
+            self.env_file, self.env_db, backup_function=self.mock_run_once())
         self.assertFalse(self.parser.error.called)
 
     def test_error(self, mock_save):
@@ -292,9 +295,15 @@
         # occurs while saving the new environments database.
         mock_save.side_effect = OSError(b'bad wolf')
         self.save_callable(self.env_db)
-        mock_save.assert_called_once_with(self.env_file, self.env_db)
+        mock_save.assert_called_once_with(
+            self.env_file, self.env_db, backup_function=self.mock_run_once())
         self.parser.error.assert_called_once_with('bad wolf')
 
+    def test_backup_function(self, mock_save):
+        # The backup function is correctly created.
+        self.save_callable(self.env_db)
+        self.mock_run_once.assert_called_once_with(shutil.copyfile)
+
 
 class TestStartInteractiveSession(
         helpers.EnvFileTestsMixin, unittest.TestCase):
 
=== modified file 'quickstart/tests/test_utils.py'
--- quickstart/tests/test_utils.py	2014-01-09 12:31:30 +0000
+++ quickstart/tests/test_utils.py	2014-01-13 16:51:49 +0000
@@ -601,6 +601,25 @@
         self.assertEqual('zydeco', bsn_series)
 
 
+class TestRunOnce(unittest.TestCase):
+
+    def setUp(self):
+        self.results = []
+        self.func = utils.run_once(self.results.append)
+
+    def test_runs_once(self):
+        # The wrapped function runs only the first time it is invoked.
+        self.func(1)
+        self.assertEqual([1], self.results)
+        self.func(2)
+        self.assertEqual([1], self.results)
+
+    def test_wrapped(self):
+        # The wrapped function looks like the original one.
+        self.assertEqual('append', self.func.__name__)
+        self.assertEqual(list.append.__doc__, self.func.__doc__)
+
+
 class TestUnitChanges(unittest.TestCase):
 
     unit = 'django/42'
 
=== modified file 'quickstart/utils.py'
--- quickstart/utils.py	2014-01-09 11:22:54 +0000
+++ quickstart/utils.py	2014-01-13 16:51:49 +0000
@@ -24,6 +24,7 @@
 import collections
 import datetime
 import errno
+import functools
 import httplib
 import json
 import logging
@@ -326,6 +327,20 @@
     return parse_status_output(output, ['machines', '0', 'series'])
 
 
+def run_once(function):
+    """Return a decorated version of the given function which runs only once.
+
+    Subsequent runs are just ignored and return None.
+    """
+    @functools.wraps(function)
+    def decorated(*args, **kwargs):
+        if not decorated.called:
+            decorated.called = True
+            return function(*args, **kwargs)
+    decorated.called = False
+    return decorated
+
+
 def unit_changes(unit_name, changeset):
     """Parse the changeset and return the change related to the given unit.