source: package_tags/sipb-xen-www/1/code/webcommon.py @ 2758

Last change on this file since 2758 was 264, checked in by ecprice, 16 years ago

Fix bug during create/delete clearing the cache

File size: 1.7 KB
Line 
1"""Exceptions for the web interface."""
2
3from sipb_xen_database import Machine, MachineAccess
4
5class MyException(Exception):
6    """Base class for my exceptions"""
7    pass
8
9class InvalidInput(MyException):
10    """Exception for user-provided input is invalid but maybe in good faith.
11
12    This would include setting memory to negative (which might be a
13    typo) but not setting an invalid boot CD (which requires bypassing
14    the select box).
15    """
16    def __init__(self, err_field, err_value, expl=None):
17        MyException.__init__(self, expl)
18        self.err_field = err_field
19        self.err_value = err_value
20
21class CodeError(MyException):
22    """Exception for internal errors or bad faith input."""
23    pass
24
25import controls
26
27def cachedproperty(func):
28    name = '__cache_' + func.__name__ + '_' + str(id(func))
29    def getter(self):
30        try:
31            return getattr(self, name)
32        except AttributeError:
33            value = func(self)
34            setattr(self, name, value)
35            return value
36    return property(getter)
37
38class Global(object):
39    """Global state of the system, to avoid duplicate remctls to get state"""
40    def __init__(self, user):
41        self.user = user
42   
43    machines = cachedproperty(lambda self: 
44                             [ma.machine for ma in 
45                              MachineAccess.select_by(user=self.user)])
46    uptimes = cachedproperty(lambda self: 
47                             controls.getUptimes(self.machines))
48
49    def clear(self):
50        """Clear the state so future accesses reload it."""
51        for attr in list(self.__dict__):
52            if attr.startswith('__cache_'):
53                delattr(self, attr)
54
55g = Global(None)
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