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+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+#
+# Copyright 2014-2015 Canonical Limited.
+#
+# 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.
+#
+# Authors:
+# Kapil Thangavelu <kapil.foss@gmail.com>
+#
+"""
+Intro
+-----
+
+A simple way to store state in units. This provides a key value
+storage with support for versioned, transactional operation,
+and can calculate deltas from previous values to simplify unit logic
+when processing changes.
+
+
+Hook Integration
+----------------
+
+There are several extant frameworks for hook execution, including
+
+ - charmhelpers.core.hookenv.Hooks
+ - charmhelpers.core.services.ServiceManager
+
+The storage classes are framework agnostic, one simple integration is
+via the HookData contextmanager. It will record the current hook
+execution environment (including relation data, config data, etc.),
+setup a transaction and allow easy access to the changes from
+previously seen values. One consequence of the integration is the
+reservation of particular keys ('rels', 'unit', 'env', 'config',
+'charm_revisions') for their respective values.
+
+Here's a fully worked integration example using hookenv.Hooks::
+
+ from charmhelper.core import hookenv, unitdata
+
+ hook_data = unitdata.HookData()
+ db = unitdata.kv()
+ hooks = hookenv.Hooks()
+
+ @hooks.hook
+ def config_changed():
+ # Print all changes to configuration from previously seen
+ # values.
+ for changed, (prev, cur) in hook_data.conf.items():
+ print('config changed', changed,
+ 'previous value', prev,
+ 'current value', cur)
+
+ # Get some unit specific bookeeping
+ if not db.get('pkg_key'):
+ key = urllib.urlopen('https://example.com/pkg_key').read()
+ db.set('pkg_key', key)
+
+ # Directly access all charm config as a mapping.
+ conf = db.getrange('config', True)
+
+ # Directly access all relation data as a mapping
+ rels = db.getrange('rels', True)
+
+ if __name__ == '__main__':
+ with hook_data():
+ hook.execute()
+
+
+A more basic integration is via the hook_scope context manager which simply
+manages transaction scope (and records hook name, and timestamp)::
+
+ >>> from unitdata import kv
+ >>> db = kv()
+ >>> with db.hook_scope('install'):
+ ... # do work, in transactional scope.
+ ... db.set('x', 1)
+ >>> db.get('x')
+ 1
+
+
+Usage
+-----
+
+Values are automatically json de/serialized to preserve basic typing
+and complex data struct capabilities (dicts, lists, ints, booleans, etc).
+
+Individual values can be manipulated via get/set::
+
+ >>> kv.set('y', True)
+ >>> kv.get('y')
+ True
+
+ # We can set complex values (dicts, lists) as a single key.
+ >>> kv.set('config', {'a': 1, 'b': True'})
+
+ # Also supports returning dictionaries as a record which
+ # provides attribute access.
+ >>> config = kv.get('config', record=True)
+ >>> config.b
+ True
+
+
+Groups of keys can be manipulated with update/getrange::
+
+ >>> kv.update({'z': 1, 'y': 2}, prefix="gui.")
+ >>> kv.getrange('gui.', strip=True)
+ {'z': 1, 'y': 2}
+
+When updating values, its very helpful to understand which values
+have actually changed and how have they changed. The storage
+provides a delta method to provide for this::
+
+ >>> data = {'debug': True, 'option': 2}
+ >>> delta = kv.delta(data, 'config.')
+ >>> delta.debug.previous
+ None
+ >>> delta.debug.current
+ True
+ >>> delta
+ {'debug': (None, True), 'option': (None, 2)}
+
+Note the delta method does not persist the actual change, it needs to
+be explicitly saved via 'update' method::
+
+ >>> kv.update(data, 'config.')
+
+Values modified in the context of a hook scope retain historical values
+associated to the hookname.
+
+ >>> with db.hook_scope('config-changed'):
+ ... db.set('x', 42)
+ >>> db.gethistory('x')
+ [(1, u'x', 1, u'install', u'2015-01-21T16:49:30.038372'),
+ (2, u'x', 42, u'config-changed', u'2015-01-21T16:49:30.038786')]
+
+"""
+
+import collections
+import contextlib
+import datetime
+import itertools
+import json
+import os
+import pprint
+import sqlite3
+import sys
+
+__author__ = 'Kapil Thangavelu <kapil.foss@gmail.com>'
+
+
+class Storage(object):
+ """Simple key value database for local unit state within charms.
+
+ Modifications are not persisted unless :meth:`flush` is called.
+
+ To support dicts, lists, integer, floats, and booleans values
+ are automatically json encoded/decoded.
+ """
+ def __init__(self, path=None):
+ self.db_path = path
+ if path is None:
+ if 'UNIT_STATE_DB' in os.environ:
+ self.db_path = os.environ['UNIT_STATE_DB']
+ else:
+ self.db_path = os.path.join(
+ os.environ.get('CHARM_DIR', ''), '.unit-state.db')
+ self.conn = sqlite3.connect('%s' % self.db_path)
+ self.cursor = self.conn.cursor()
+ self.revision = None
+ self._closed = False
+ self._init()
+
+ def close(self):
+ if self._closed:
+ return
+ self.flush(False)
+ self.cursor.close()
+ self.conn.close()
+ self._closed = True
+
+ def get(self, key, default=None, record=False):
+ self.cursor.execute('select data from kv where key=?', [key])
+ result = self.cursor.fetchone()
+ if not result:
+ return default
+ if record:
+ return Record(json.loads(result[0]))
+ return json.loads(result[0])
+
+ def getrange(self, key_prefix, strip=False):
+ """
+ Get a range of keys starting with a common prefix as a mapping of
+ keys to values.
+
+ :param str key_prefix: Common prefix among all keys
+ :param bool strip: Optionally strip the common prefix from the key
+ names in the returned dict
+ :return dict: A (possibly empty) dict of key-value mappings
+ """
+ self.cursor.execute("select key, data from kv where key like ?",
+ ['%s%%' % key_prefix])
+ result = self.cursor.fetchall()
+
+ if not result:
+ return {}
+ if not strip:
+ key_prefix = ''
+ return dict([
+ (k[len(key_prefix):], json.loads(v)) for k, v in result])
+
+ def update(self, mapping, prefix=""):
+ """
+ Set the values of multiple keys at once.
+
+ :param dict mapping: Mapping of keys to values
+ :param str prefix: Optional prefix to apply to all keys in `mapping`
+ before setting
+ """
+ for k, v in mapping.items():
+ self.set("%s%s" % (prefix, k), v)
+
+ def unset(self, key):
+ """
+ Remove a key from the database entirely.
+ """
+ self.cursor.execute('delete from kv where key=?', [key])
+ if self.revision and self.cursor.rowcount:
+ self.cursor.execute(
+ 'insert into kv_revisions values (?, ?, ?)',
+ [key, self.revision, json.dumps('DELETED')])
+
+ def unsetrange(self, keys=None, prefix=""):
+ """
+ Remove a range of keys starting with a common prefix, from the database
+ entirely.
+
+ :param list keys: List of keys to remove.
+ :param str prefix: Optional prefix to apply to all keys in ``keys``
+ before removing.
+ """
+ if keys is not None:
+ keys = ['%s%s' % (prefix, key) for key in keys]
+ self.cursor.execute('delete from kv where key in (%s)' % ','.join(['?'] * len(keys)), keys)
+ if self.revision and self.cursor.rowcount:
+ self.cursor.execute(
+ 'insert into kv_revisions values %s' % ','.join(['(?, ?, ?)'] * len(keys)),
+ list(itertools.chain.from_iterable((key, self.revision, json.dumps('DELETED')) for key in keys)))
+ else:
+ self.cursor.execute('delete from kv where key like ?',
+ ['%s%%' % prefix])
+ if self.revision and self.cursor.rowcount:
+ self.cursor.execute(
+ 'insert into kv_revisions values (?, ?, ?)',
+ ['%s%%' % prefix, self.revision, json.dumps('DELETED')])
+
+ def set(self, key, value):
+ """
+ Set a value in the database.
+
+ :param str key: Key to set the value for
+ :param value: Any JSON-serializable value to be set
+ """
+ serialized = json.dumps(value)
+
+ self.cursor.execute('select data from kv where key=?', [key])
+ exists = self.cursor.fetchone()
+
+ # Skip mutations to the same value
+ if exists:
+ if exists[0] == serialized:
+ return value
+
+ if not exists:
+ self.cursor.execute(
+ 'insert into kv (key, data) values (?, ?)',
+ (key, serialized))
+ else:
+ self.cursor.execute('''
+ update kv
+ set data = ?
+ where key = ?''', [serialized, key])
+
+ # Save
+ if not self.revision:
+ return value
+
+ self.cursor.execute(
+ 'select 1 from kv_revisions where key=? and revision=?',
+ [key, self.revision])
+ exists = self.cursor.fetchone()
+
+ if not exists:
+ self.cursor.execute(
+ '''insert into kv_revisions (
+ revision, key, data) values (?, ?, ?)''',
+ (self.revision, key, serialized))
+ else:
+ self.cursor.execute(
+ '''
+ update kv_revisions
+ set data = ?
+ where key = ?
+ and revision = ?''',
+ [serialized, key, self.revision])
+
+ return value
+
+ def delta(self, mapping, prefix):
+ """
+ return a delta containing values that have changed.
+ """
+ previous = self.getrange(prefix, strip=True)
+ if not previous:
+ pk = set()
+ else:
+ pk = set(previous.keys())
+ ck = set(mapping.keys())
+ delta = DeltaSet()
+
+ # added
+ for k in ck.difference(pk):
+ delta[k] = Delta(None, mapping[k])
+
+ # removed
+ for k in pk.difference(ck):
+ delta[k] = Delta(previous[k], None)
+
+ # changed
+ for k in pk.intersection(ck):
+ c = mapping[k]
+ p = previous[k]
+ if c != p:
+ delta[k] = Delta(p, c)
+
+ return delta
+
+ @contextlib.contextmanager
+ def hook_scope(self, name=""):
+ """Scope all future interactions to the current hook execution
+ revision."""
+ assert not self.revision
+ self.cursor.execute(
+ 'insert into hooks (hook, date) values (?, ?)',
+ (name or sys.argv[0],
+ datetime.datetime.utcnow().isoformat()))
+ self.revision = self.cursor.lastrowid
+ try:
+ yield self.revision
+ self.revision = None
+ except:
+ self.flush(False)
+ self.revision = None
+ raise
+ else:
+ self.flush()
+
+ def flush(self, save=True):
+ if save:
+ self.conn.commit()
+ elif self._closed:
+ return
+ else:
+ self.conn.rollback()
+
+ def _init(self):
+ self.cursor.execute('''
+ create table if not exists kv (
+ key text,
+ data text,
+ primary key (key)
+ )''')
+ self.cursor.execute('''
+ create table if not exists kv_revisions (
+ key text,
+ revision integer,
+ data text,
+ primary key (key, revision)
+ )''')
+ self.cursor.execute('''
+ create table if not exists hooks (
+ version integer primary key autoincrement,
+ hook text,
+ date text
+ )''')
+ self.conn.commit()
+
+ def gethistory(self, key, deserialize=False):
+ self.cursor.execute(
+ '''
+ select kv.revision, kv.key, kv.data, h.hook, h.date
+ from kv_revisions kv,
+ hooks h
+ where kv.key=?
+ and kv.revision = h.version
+ ''', [key])
+ if deserialize is False:
+ return self.cursor.fetchall()
+ return map(_parse_history, self.cursor.fetchall())
+
+ def debug(self, fh=sys.stderr):
+ self.cursor.execute('select * from kv')
+ pprint.pprint(self.cursor.fetchall(), stream=fh)
+ self.cursor.execute('select * from kv_revisions')
+ pprint.pprint(self.cursor.fetchall(), stream=fh)
+
+
+def _parse_history(d):
+ return (d[0], d[1], json.loads(d[2]), d[3],
+ datetime.datetime.strptime(d[-1], "%Y-%m-%dT%H:%M:%S.%f"))
+
+
+class HookData(object):
+ """Simple integration for existing hook exec frameworks.
+
+ Records all unit information, and stores deltas for processing
+ by the hook.
+
+ Sample::
+
+ from charmhelper.core import hookenv, unitdata
+
+ changes = unitdata.HookData()
+ db = unitdata.kv()
+ hooks = hookenv.Hooks()
+
+ @hooks.hook
+ def config_changed():
+ # View all changes to configuration
+ for changed, (prev, cur) in changes.conf.items():
+ print('config changed', changed,
+ 'previous value', prev,
+ 'current value', cur)
+
+ # Get some unit specific bookeeping
+ if not db.get('pkg_key'):
+ key = urllib.urlopen('https://example.com/pkg_key').read()
+ db.set('pkg_key', key)
+
+ if __name__ == '__main__':
+ with changes():
+ hook.execute()
+
+ """
+ def __init__(self):
+ self.kv = kv()
+ self.conf = None
+ self.rels = None
+
+ @contextlib.contextmanager
+ def __call__(self):
+ from charmhelpers.core import hookenv
+ hook_name = hookenv.hook_name()
+
+ with self.kv.hook_scope(hook_name):
+ self._record_charm_version(hookenv.charm_dir())
+ delta_config, delta_relation = self._record_hook(hookenv)
+ yield self.kv, delta_config, delta_relation
+
+ def _record_charm_version(self, charm_dir):
+ # Record revisions.. charm revisions are meaningless
+ # to charm authors as they don't control the revision.
+ # so logic dependnent on revision is not particularly
+ # useful, however it is useful for debugging analysis.
+ charm_rev = open(
+ os.path.join(charm_dir, 'revision')).read().strip()
+ charm_rev = charm_rev or '0'
+ revs = self.kv.get('charm_revisions', [])
+ if charm_rev not in revs:
+ revs.append(charm_rev.strip() or '0')
+ self.kv.set('charm_revisions', revs)
+
+ def _record_hook(self, hookenv):
+ data = hookenv.execution_environment()
+ self.conf = conf_delta = self.kv.delta(data['conf'], 'config')
+ self.rels = rels_delta = self.kv.delta(data['rels'], 'rels')
+ self.kv.set('env', dict(data['env']))
+ self.kv.set('unit', data['unit'])
+ self.kv.set('relid', data.get('relid'))
+ return conf_delta, rels_delta
+
+
+class Record(dict):
+
+ __slots__ = ()
+
+ def __getattr__(self, k):
+ if k in self:
+ return self[k]
+ raise AttributeError(k)
+
+
+class DeltaSet(Record):
+
+ __slots__ = ()
+
+
+Delta = collections.namedtuple('Delta', ['previous', 'current'])
+
+
+_KV = None
+
+
+def kv():
+ global _KV
+ if _KV is None:
+ _KV = Storage()
+ return _KV