zc.objectlog 0.1

Customizable object log for Zope3

The objectlog package provides a customizable log for a single object. The system was designed to provide information for a visual log of important object changes and to provide analyzable information for metrics.

• It provides automatic recording for each log entry of a timestamp and the principals in the request when the log was made.

• Given a schema of data to collect about the object, it automatically calculates and stores changesets from the last log entry, primarily to provide a quick and easy answer to the question “what changed?” and secondarily to reduce database size.

• It accepts optional summary and detail values that allow the system or users to annotate the entries with human-readable messages.

• It allows each log entry to be annotated with zero or more marker interfaces so that log entries may be classified with an interface.

For more information about using zc.objectlog, see:

src/zc/objectlog/log.txt

objectlog

The objectlog package provides a customizable log for a single object. The system was designed to provide information for a visual log of important object changes and to provide analyzable information for metrics.

• It provides automatic recording for each log entry of a timestamp and the principals in the request when the log was made.

• Given a schema of data to collect about the object, it automatically calculates and stores changesets from the last log entry, primarily to provide a quick and easy answer to the question “what changed?” and secondarily to reduce database size.

• It accepts optional summary and detail values that allow the system or users to annotate the entries with human-readable messages.

• It allows each log entry to be annotated with zero or more marker interfaces so that log entries may be classified with an interface.

Moreover, the log entries can be set to occur at transition boundaries, and to only ocur if a change was made (according to the changeset) since the last log entry.

To show this, we need to set up a dummy interaction. We do this below, then create an object with a log, then actually make a log.

>>> import zope.security.management
>>> import zope.security.interfaces
>>> import zope.app.security.interfaces
>>> from zope import interface, schema
>>> from zope.app.testing import ztapi
>>> class DummyPrincipal(object):
...     interface.implements(zope.security.interfaces.IPrincipal)
...     def __init__(self, id, title, description):
...         self.id = id
...         self.title = title
...         self.description = description
...
>>> alice = DummyPrincipal('alice', 'Alice Aal', 'first principal')
>>> betty = DummyPrincipal('betty', 'Betty Barnes', 'second principal')
>>> cathy = DummyPrincipal('cathy', 'Cathy Camero', 'third principal')
>>> class DummyParticipation(object):
...     interface.implements(zope.security.interfaces.IParticipation)
...     interaction = principal = None
...     def __init__(self, principal):
...         self.principal = principal
...
>>> class DummyAuthService(object):
...     interface.implements(zope.app.security.interfaces.IAuthentication)
...     def __init__(self, data):
...         self.data = data
...     def getPrincipal(self, id):
...         return self.data[id]
...
>>> auth = DummyAuthService(
...     {'alice': alice, 'betty': betty, 'cathy': cathy})
>>> ztapi.provideUtility(
...     zope.app.security.interfaces.IAuthentication, auth)
>>> import zope.publisher.interfaces

>>> import zc.objectlog
>>> import zope.location
>>> WORKING = u"Where I'm working"
>>> COUCH = u"On couch"
>>> BED = u"On bed"
>>> KITCHEN = u"In kitchen"
>>> class ICat(interface.Interface):
...     name = schema.TextLine(title=u"Name", required=True)
...     location = schema.Choice(
...         (WORKING, COUCH, BED, KITCHEN),
...         title=u"Location", required=False)
...     weight = schema.Int(title=u"Weight in Pounds", required=True)
...     getAge, = schema.accessors(
...         schema.Int(title=u"Age in Years", readonly=True,
...         required=False))
...
>>> import persistent
>>> class Cat(persistent.Persistent):
...     interface.implements(ICat)
...     def __init__(self, name, weight, age, location=None):
...         self.name = name
...         self.weight = weight
...         self.location = location
...         self._age = age
...         self.log = zc.objectlog.Log(ICat)
...         zope.location.locate(self.log, self, 'log')
...     def getAge(self):
...         return self._age
...

Notice in the __init__ for cat that we located the log on the cat. This is an important step, as it enables the automatic changesets.

Now we are set up to look at examples. With one exception, each example runs within a faux interaction so we can see how the principal_ids attribute works. First we’ll see that len works, that the record_schema attribute is set properly, that the timestamp uses a pytz.utc timezone for the timestamp, that log iteration works, and that summary, details, and data were set properly.

>>> import pytz, datetime
>>> a_p = DummyParticipation(alice)
>>> interface.directlyProvides(a_p, zope.publisher.interfaces.IRequest)
>>> zope.security.management.newInteraction(a_p)
>>> emily = Cat(u'Emily', 16, 5, WORKING)
>>> len(emily.log)
0
>>> emily.log.record_schema is ICat
True
>>> before = datetime.datetime.now(pytz.utc)
>>> entry = emily.log(
...     u'Starting to keep track of Emily',
...     u'Looks like\nshe might go upstairs soon')
>>> entry is emily.log[0]
True
>>> after = datetime.datetime.now(pytz.utc)
>>> len(emily.log)
1
>>> before <= entry.timestamp <= after
True
>>> entry.timestamp.tzinfo is pytz.utc
True
>>> entry.principal_ids
('alice',)
>>> list(emily.log) == [entry]
True
>>> entry.record_schema is ICat
True
>>> entry.summary
u'Starting to keep track of Emily'
>>> entry.details
u'Looks like\nshe might go upstairs soon'

The record and the record_changes should have a full set of values from the object. The record has a special security checker that allows users to access any field defined on the schema, but not to access any others nor to write any values.

>>> record = emily.log[0].record
>>> record.name
u'Emily'
>>> record.location==WORKING
True
>>> record.weight
16
>>> record.getAge()
5
>>> ICat.providedBy(record)
True
>>> emily.log[0].record_changes == {
... 'name': u'Emily', 'weight': 16, 'location': u"Where I'm working",
... 'getAge': 5}
True
>>> from zope.security.checker import ProxyFactory
>>> proxrecord = ProxyFactory(record)
>>> ICat.providedBy(proxrecord)
True
>>> from zc.objectlog import interfaces
>>> interfaces.IRecord.providedBy(proxrecord)
True
>>> from zope.security import canAccess, canWrite
>>> canAccess(record, 'name')
True
>>> canAccess(record, 'weight')
True
>>> canAccess(record, 'location')
True
>>> canAccess(record, 'getAge')
True
>>> canAccess(record, 'shazbot') # doctest: +ELLIPSIS
Traceback (most recent call last):
...
ForbiddenAttribute: ('shazbot', ...
>>> canWrite(record, 'name')
False
>>> zope.security.management.endInteraction()

Interactions with multiple principals are correctly recorded as well. Note that non-request participations are not included in the records. We also look a bit more at the record and the change set.

>>> a_p = DummyParticipation(alice)
>>> b_p = DummyParticipation(betty)
>>> c_p = DummyParticipation(cathy)
>>> interface.directlyProvides(a_p, zope.publisher.interfaces.IRequest)
>>> interface.directlyProvides(b_p, zope.publisher.interfaces.IRequest)
>>> zope.security.management.newInteraction(a_p, b_p, c_p)
>>> emily.location = KITCHEN
>>> entry = emily.log(u"Sounds like she's eating", u"Dry food,\nin fact.")
>>> len(emily.log)
2
>>> emily.log[0].summary
u'Starting to keep track of Emily'
>>> emily.log[1].summary
u"Sounds like she's eating"
>>> after <= emily.log[1].timestamp <= datetime.datetime.now(pytz.utc)
True
>>> emily.log[1].principal_ids # cathy was not a request, so not included
('alice', 'betty')
>>> emily.log[1].details
u'Dry food,\nin fact.'
>>> emily.log[1].record_changes
{'location': u'In kitchen'}
>>> record = emily.log[1].record
>>> record.location
u'In kitchen'
>>> record.name
u'Emily'
>>> record.weight
16
>>> zope.security.management.endInteraction()

It is possible to make a log without an interaction as well.

>>> emily._age = 6
>>> entry = emily.log(u'Happy Birthday') # no interaction
>>> len(emily.log)
3
>>> emily.log[2].principal_ids
()
>>> emily.log[2].record_changes
{'getAge': 6}
>>> record = emily.log[2].record
>>> record.location
u'In kitchen'
>>> record.name
u'Emily'
>>> record.weight
16
>>> record.getAge()
6

Entries may be marked with marker interfaces to categorize them. This approach may be difficult with security proxies, so it may be changed. We’ll do all the rest of our examples within the same interaction.

>>> c_p = DummyParticipation(cathy)
>>> interface.directlyProvides(c_p, zope.publisher.interfaces.IRequest)
>>> zope.security.management.newInteraction(c_p)
>>> emily.location = None
>>> emily.weight = 17
>>> class IImportantLogEntry(interface.Interface):
...     "A marker interface for log entries"
>>> interface.directlyProvides(
...     emily.log(u'Emily is in transit...and ate a bit too much'),
...     IImportantLogEntry)
>>> len(emily.log)
4
>>> [e for e in emily.log if IImportantLogEntry.providedBy(e)] == [
...     emily.log[3]]
True
>>> emily.log[3].principal_ids
('cathy',)
>>> emily.log[3].record_changes=={'weight': 17, 'location': None}
True
>>> record = emily.log[3].record
>>> old_record = emily.log[2].record
>>> record.name == old_record.name == u'Emily'
True
>>> record.weight
17
>>> old_record.weight
16
>>> record.location # None
>>> old_record.location
u'In kitchen'

Making a log will fail if the record it is trying to make does not conform to its schema.

>>> emily.location = u'Outside'
>>> emily.log(u'This should never happen')
Traceback (most recent call last):
...
ConstraintNotSatisfied: Outside
>>> len(emily.log)
4
>>> emily.location = BED

It will also fail if the arguments passed to it are not correct.

>>> emily.log("This isn't unicode so will not succeed")
Traceback (most recent call last):
...
WrongType: ("This isn't unicode so will not succeed", <type 'unicode'>)
>>> len(emily.log)
4
>>> success = emily.log(u"Yay, unicode")

The following is commented out until we have more

# >>> emily.log(u”Data without an interface won’t work”, None, ‘boo hoo’) Traceback (most recent call last): … WrongContainedType: []

Zero or more additional arbitrary data objects may be included on the log entry as long as they implement an interface.

>>> class IConsumableRecord(interface.Interface):
...     dry_food = schema.Int(
...         title=u"Dry found consumed in ounces", required=False)
...     wet_food = schema.Int(
...         title=u"Wet food consumed in ounces", required=False)
...     water = schema.Int(
...         title=u"Water consumed in teaspoons", required=False)
...

# >>> class ConsumableRecord(object): … interface.implements(IConsumableRecord) … def __init__(self, dry_food=None, wet_food=None, water=None): … self.dry_food = dry_food … self.wet_food = wet_food … self.water = water … # >>> entry = emily.log(u’Collected eating records’, None, ConsumableRecord(1)) # >>> len(emily.log) 5 # >>> len(emily.log[4].data) 1 # >>> IConsumableRecord.providedBy(emily.log[4].data[0]) True # >>> emily.log[4].data[0].dry_food 1

__getitem__ and __iter__ work as normal for a Python sequence, including support for extended slices.

>>> list(emily.log) == [emily.log[0], emily.log[1], emily.log[2],
...                     emily.log[3], emily.log[4]]
True
>>> emily.log[-1] is emily.log[4]
True
>>> emily.log[0] is emily.log[-5]
True
>>> emily.log[5]
Traceback (most recent call last):
...
IndexError: list index out of range
>>> emily.log[-6]
Traceback (most recent call last):
...
IndexError: list index out of range
>>> emily.log[4:2:-1] == [emily.log[4], emily.log[3]]
True

The log’s record_schema may be changed as long as there are no logs or the interface extends (or is) the interface for the last log.

>>> emily.log.record_schema = IConsumableRecord # doctest: +ELLIPSIS
Traceback (most recent call last):
...
ValueError: Once entries have been made, may only change schema to one...
>>> class IExtendedCat(ICat):
...     parent_object_intid = schema.Int(title=u"Parent Object")
...
>>> emily.log.record_schema = IExtendedCat
>>> emily.log.record_schema = ICat
>>> emily.log.record_schema = IExtendedCat
>>> class ExtendedCatAdapter(object):
...     interface.implements(IExtendedCat)
...     def __init__(self, cat): # getAge is left off
...         self.name = cat.name
...         self.weight = cat.weight
...         self.location = cat.location
...         self.parent_object_intid = 42
...
>>> ztapi.provideAdapter((ICat,), IExtendedCat, ExtendedCatAdapter)
>>> entry = emily.log(u'First time with extended interface')
>>> emily.log.record_schema = ICat # doctest: +ELLIPSIS
Traceback (most recent call last):
...
ValueError: Once entries have been made, may only change schema to one...
>>> emily.log[5].record_changes == {
...     'parent_object_intid': 42, 'getAge': None}
True
>>> record = emily.log[5].record
>>> record.parent_object_intid
42
>>> record.name
u'Emily'
>>> record.location
u'On bed'
>>> record.weight
17
>>> record.getAge() # None
>>> IExtendedCat.providedBy(record)
True
>>> old_record = emily.log[3].record
>>> IExtendedCat.providedBy(old_record)
False
>>> ICat.providedBy(old_record)
True
>>> old_record.parent_object_intid # doctest: +ELLIPSIS
Traceback (most recent call last):
...
AttributeError: ...

Entries support convenience next and previous attributes, which make them act like immutable doubly linked lists:

>>> entry = emily.log[5]
>>> entry.previous is emily.log[4]
True
>>> entry.next # None
>>> entry.previous.previous.previous.previous.previous is emily.log[0]
True
>>> emily.log[0].previous # None
>>> emily.log[0].next is emily.log[1]
True

Objectlogs also support deferring until the end of a transaction. To show this, we will need a sample database, a transaction, and key reference adapters. We show the simplest example first.

>>> from ZODB.tests import util
>>> import transaction

>>> db = util.DB()
>>> connection = db.open()
>>> root = connection.root()
>>> root["emily"] = emily
>>> transaction.commit()
>>> import zope.app.keyreference.persistent
>>> import zope.app.keyreference.interfaces
>>> import ZODB.interfaces
>>> import persistent.interfaces
>>> from zope import component
>>> component.provideAdapter(
...     zope.app.keyreference.persistent.KeyReferenceToPersistent,
...     (persistent.interfaces.IPersistent,),
...     zope.app.keyreference.interfaces.IKeyReference)
>>> component.provideAdapter(
...     zope.app.keyreference.persistent.connectionOfPersistent,
...     (persistent.interfaces.IPersistent,),
...     ZODB.interfaces.IConnection)

>>> len(emily.log)
6
>>> emily.log(u'This one is deferred', defer=True) # returns None: deferred!
>>> len(emily.log)
6
>>> transaction.commit()
>>> len(emily.log)
7
>>> emily.log[6].summary
u'This one is deferred'
>>> emily.log[6].record_changes
{}

While this is interesting, the point is to capture changes to the object, whether or not they happened when the log was called. Here is a more pertinent example, then.

>>> len(emily.log)
7
>>> emily.weight = 16
>>> emily.log(u'Also deferred', defer=True) # returns None: deferred!
>>> len(emily.log)
7
>>> emily.location = COUCH
>>> transaction.commit()
>>> len(emily.log)
8
>>> emily.log[7].summary
u'Also deferred'
>>> import pprint
>>> pprint.pprint(emily.log[7].record_changes)
{'location': u'On couch', 'weight': 16}

Multiple deferred log entries can be deferred, if desired.

>>> emily.log(u'One log', defer=True)
>>> emily.log(u'Two log', defer=True)
>>> len(emily.log)
8
>>> transaction.commit()
>>> len(emily.log)
10
>>> emily.log[8].summary
u'One log'
>>> emily.log[9].summary
u'Two log'

Another option is if_changed. It should not make a log unless there was a change.

>>> len(emily.log)
10
>>> emily.log(u'If changed', if_changed=True) # returns None: no change!
>>> len(emily.log)
10
>>> emily.location = BED
>>> entry = emily.log(u'If changed', if_changed=True)
>>> len(emily.log)
11
>>> emily.log[10] is entry
True
>>> entry.summary
u'If changed'
>>> pprint.pprint(entry.record_changes)
{'location': u'On bed'}
>>> transaction.commit()

The two options, if_changed and defer, can be used together. This makes for a log entry that will only be made at a transition boundary if there have been no previous changes. Note that a log entry that occurs whether or not changes were made (hereafter called a “required” log entry) that is also deferred will always eliminate any deferred if_changed log entry, even if the required log entry was registered later in the transaction.

>>> len(emily.log)
11
>>> emily.log(u'Another', defer=True, if_changed=True) # returns None
>>> transaction.commit()
>>> len(emily.log)
11
>>> emily.log(u'Yet another', defer=True, if_changed=True) # returns None
>>> emily.location = COUCH
>>> len(emily.log)
11
>>> transaction.commit()
>>> len(emily.log)
12
>>> emily.log[11].summary
u'Yet another'
>>> emily.location = KITCHEN
>>> entry = emily.log(u'non-deferred entry', if_changed=True)
>>> len(emily.log)
13
>>> entry.summary
u'non-deferred entry'
>>> emily.log(u'will not write', defer=True, if_changed=True)
>>> transaction.commit()
>>> len(emily.log)
13
>>> emily.log(u'will not write', defer=True, if_changed=True)
>>> emily.location = WORKING
>>> emily.log(u'also will not write', defer=True, if_changed=True)
>>> emily.log(u'required, deferred', defer=True)
>>> len(emily.log)
13
>>> transaction.commit()
>>> len(emily.log)
14
>>> emily.log[13].summary
u'required, deferred'

This should all work in the presence of multiple objects, of course.

>>> sam = Cat(u'Sam', 20, 4)
>>> root['sam'] = sam
>>> transaction.commit()
>>> sam.weight = 19
>>> sam.log(u'Auto log', defer=True, if_changed=True)
>>> sam.log(u'Sam lost weight!', defer=True)
>>> sam.log(u'Saw sam today', defer=True)
>>> emily.log(u'Auto log', defer=True, if_changed=True)
>>> emily.weight = 15
>>> transaction.commit()
>>> len(sam.log)
2
>>> sam.log[0].summary
u'Sam lost weight!'
>>> sam.log[1].summary
u'Saw sam today'
>>> len(emily.log)
15
>>> emily.log[14].summary
u'Auto log'

>>> # TEAR DOWN
>>> zope.security.management.endInteraction()
>>> ztapi.unprovideUtility(zope.app.security.interfaces.IAuthentication)