Move CacheStorage to its own module.

And rename it to JobCache. The word "Cache" already implies "Storage"
so it makes more sense to name it after the things that it
stores...Jobs!

Change-Id: If7a7a56e8f6a3637f62e285eaa7ba989f67002dc

1 files changed, 117 insertions, 0 deletions

diff --git a/jenkins_jobs/cache.py b/jenkins_jobs/cache.py
new file mode 100644
index 00000000..ee293d46
--- /dev/null
+++ b/jenkins_jobs/cache.py
@@ -0,0 +1,117 @@
+#!/usr/bin/env python
+# Copyright (C) 2012 OpenStack, LLC.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+# Manage jobs in Jenkins server
+
+import errno
+import io
+import logging
+import os
+import re
+import tempfile
+import yaml
+
+
+logger = logging.getLogger(__name__)
+
+
+class JobCache(object):
+    # ensure each instance of the class has a reference to the required
+    # modules so that they are available to be used when the destructor
+    # is being called since python will not guarantee that it won't have
+    # removed global module references during teardown.
+    _logger = logger
+    _os = os
+    _tempfile = tempfile
+    _yaml = yaml
+
+    def __init__(self, jenkins_url, flush=False):
+        cache_dir = self.get_cache_dir()
+        # One cache per remote Jenkins URL:
+        host_vary = re.sub('[^A-Za-z0-9\-\~]', '_', jenkins_url)
+        self.cachefilename = os.path.join(
+            cache_dir, 'cache-host-jobs-' + host_vary + '.yml')
+        if flush or not os.path.isfile(self.cachefilename):
+            self.data = {}
+        else:
+            with io.open(self.cachefilename, 'r', encoding='utf-8') as yfile:
+                self.data = yaml.load(yfile)
+        logger.debug("Using cache: '{0}'".format(self.cachefilename))
+
+    @staticmethod
+    def get_cache_dir():
+        home = os.path.expanduser('~')
+        if home == '~':
+            raise OSError('Could not locate home folder')
+        xdg_cache_home = os.environ.get('XDG_CACHE_HOME') or \
+            os.path.join(home, '.cache')
+        path = os.path.join(xdg_cache_home, 'jenkins_jobs')
+        if not os.path.isdir(path):
+            try:
+                os.makedirs(path)
+            except OSError as ose:
+                # it could happen that two jjb instances are running at the
+                # same time and that the other instance created the directory
+                # after we made the check, in which case there is no error
+                if ose.errno != errno.EEXIST:
+                    raise ose
+        return path
+
+    def set(self, job, md5):
+        self.data[job] = md5
+
+    def clear(self):
+        self.data.clear()
+
+    def is_cached(self, job):
+        if job in self.data:
+            return True
+        return False
+
+    def has_changed(self, job, md5):
+        if job in self.data and self.data[job] == md5:
+            return False
+        return True
+
+    def save(self):
+        # use self references to required modules in case called via __del__
+        # write to tempfile under same directory and then replace to avoid
+        # issues around corruption such the process be killed
+        tfile = self._tempfile.NamedTemporaryFile(dir=self.get_cache_dir(),
+                                                  delete=False)
+        tfile.write(self._yaml.dump(self.data).encode('utf-8'))
+        # force contents to be synced on disk before overwriting cachefile
+        tfile.flush()
+        self._os.fsync(tfile.fileno())
+        tfile.close()
+        try:
+            self._os.rename(tfile.name, self.cachefilename)
+        except OSError:
+            # On Windows, if dst already exists, OSError will be raised even if
+            # it is a file. Remove the file first in that case and try again.
+            self._os.remove(self.cachefilename)
+            self._os.rename(tfile.name, self.cachefilename)
+
+        self._logger.debug("Cache written out to '%s'" % self.cachefilename)
+
+    def __del__(self):
+        # check we initialized sufficiently in case called
+        # due to an exception occurring in the __init__
+        if getattr(self, 'data', None) is not None:
+            try:
+                self.save()
+            except Exception as e:
+                self._logger.error("Failed to write to cache file '%s' on "
+                                   "exit: %s" % (self.cachefilename, e))