Add 'migrator' for handling config name changes and consistency

This migrator module does a few things
 * fixes filename markers that were written with a '-' in them to have
   an '_' instead
 * support renaming modules.  Explicitly this handles the name change
   of 'apt-update-upgrade' to 'apt-configure' and
   'package-update-upgrade-install'

Also, just be more consistent everywhere where writing semaphore/marker
files and use '_' instead of '-' (canon_sem_name).

cloudinit/config/cc_migrator.py

@@ -0,0 +1,83 @@
+# vi: ts=4 expandtab
+#
+#    Copyright (C) 2012 Yahoo! Inc.
+#
+#    Author: Joshua Harlow <harlowja@yahoo-inc.com>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License version 3, as
+#    published by the Free Software Foundation.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import os
+import shutil
+
+from cloudinit import helpers
+from cloudinit import util
+
+from cloudinit.settings import PER_ALWAYS
+
+frequency = PER_ALWAYS
+
+
+def _migrate_canon_sems(cloud):
+    sem_path = cloud.paths.get_ipath('sem')
+    if not sem_path or not os.path.exists(sem_path):
+        return 0
+    am_adjusted = 0
+    for p in os.listdir(sem_path):
+        full_path = os.path.join(sem_path, p)
+        if os.path.isfile(full_path):
+            (name, ext) = os.path.splitext(p)
+            canon_name = helpers.canon_sem_name(name)
+            if canon_name != name:
+                new_path = os.path.join(sem_path, canon_name + ext)
+                shutil.move(full_path, new_path)
+                am_adjusted += 1
+    return am_adjusted
+
+
+def _migrate_legacy_sems(cloud, log):
+    sem_path = cloud.paths.get_ipath('sem')
+    if not sem_path or not os.path.exists(sem_path):
+        return
+    legacy_adjust = {
+        'apt-update-upgrade': [
+            'apt-configure',
+            'package-update-upgrade-install',
+        ],
+    }
+    sem_helper = helpers.FileSemaphores(sem_path)
+    for (mod_name, migrate_to) in legacy_adjust.items():
+        possibles = [mod_name, helpers.canon_sem_name(mod_name)]
+        old_exists = []
+        for p in os.listdir(sem_path):
+            (name, _ext) = os.path.splitext(p)
+            if name in possibles and os.path.isfile(p):
+                old_exists.append(p)
+        for p in old_exists:
+            util.del_file(os.path.join(sem_path, p))
+            (_name, freq) = os.path.splitext(p)
+            for m in migrate_to:
+                log.debug("Migrating %s => %s with the same frequency",
+                          p, m)
+                with sem_helper.lock(m, freq):
+                    pass
+
+
+def handle(name, cfg, cloud, log, _args):
+    do_migrate = util.get_cfg_option_str(cfg, "migrate", True)
+    if not util.translate_bool(do_migrate):
+        log.debug("Skipping module named %s, migration disabled", name)
+        return
+    sems_moved = _migrate_canon_sems(cloud)
+    log.debug("Migrated %s semaphore files to there canonicalized names",
+              sems_moved)
+    _migrate_legacy_sems(cloud, log)

cloudinit/helpers.py

@@ -71,12 +71,17 @@ class FileLock(object):
         return "<%s using file %r>" % (util.obj_name(self), self.fn)
 
 
+def canon_sem_name(name):
+    return name.replace("-", "_")
+
+
 class FileSemaphores(object):
-    def __init__(self, sem_path):
+    def __init__(self, sem_path):   
         self.sem_path = sem_path
 
     @contextlib.contextmanager
     def lock(self, name, freq, clear_on_fail=False):
+        name = canon_sem_name(name)
         try:
             yield self._acquire(name, freq)
         except:
@@ -85,6 +90,7 @@ class FileSemaphores(object):
             raise
 
     def clear(self, name, freq):
+        name = canon_sem_name(name)
         sem_file = self._get_path(name, freq)
         try:
             util.del_file(sem_file)
@@ -119,6 +125,7 @@ class FileSemaphores(object):
     def has_run(self, name, freq):
         if not freq or freq == PER_ALWAYS:
             return False
+        name = canon_sem_name(name)
         sem_file = self._get_path(name, freq)
         # This isn't really a good atomic check
         # but it suffices for where and when cloudinit runs

config/cloud.cfg

@@ -23,6 +23,7 @@ preserve_hostname: false
 
 # The modules that run in the 'init' stage
 cloud_init_modules:
+ - migrator
  - bootcmd
  - write-files
  - resizefs