aboutsummaryrefslogtreecommitdiffstats
path: root/keystone-moon/keystone/openstack/common/loopingcall.py
blob: 39eed47d81d66d1d11c73ac8e27c0741132b17ee (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
# Copyright 2010 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
# Copyright 2011 Justin Santa Barbara
# All Rights Reserved.
#
#    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.

import logging
import sys
import time

from eventlet import event
from eventlet import greenthread

from keystone.openstack.common._i18n import _LE, _LW

LOG = logging.getLogger(__name__)

# NOTE(zyluo): This lambda function was declared to avoid mocking collisions
#              with time.time() called in the standard logging module
#              during unittests.
_ts = lambda: time.time()


class LoopingCallDone(Exception):
    """Exception to break out and stop a LoopingCallBase.

    The poll-function passed to LoopingCallBase can raise this exception to
    break out of the loop normally. This is somewhat analogous to
    StopIteration.

    An optional return-value can be included as the argument to the exception;
    this return-value will be returned by LoopingCallBase.wait()

    """

    def __init__(self, retvalue=True):
        """:param retvalue: Value that LoopingCallBase.wait() should return."""
        self.retvalue = retvalue


class LoopingCallBase(object):
    def __init__(self, f=None, *args, **kw):
        self.args = args
        self.kw = kw
        self.f = f
        self._running = False
        self.done = None

    def stop(self):
        self._running = False

    def wait(self):
        return self.done.wait()


class FixedIntervalLoopingCall(LoopingCallBase):
    """A fixed interval looping call."""

    def start(self, interval, initial_delay=None):
        self._running = True
        done = event.Event()

        def _inner():
            if initial_delay:
                greenthread.sleep(initial_delay)

            try:
                while self._running:
                    start = _ts()
                    self.f(*self.args, **self.kw)
                    end = _ts()
                    if not self._running:
                        break
                    delay = end - start - interval
                    if delay > 0:
                        LOG.warn(_LW('task %(func_name)r run outlasted '
                                     'interval by %(delay).2f sec'),
                                 {'func_name': self.f, 'delay': delay})
                    greenthread.sleep(-delay if delay < 0 else 0)
            except LoopingCallDone as e:
                self.stop()
                done.send(e.retvalue)
            except Exception:
                LOG.exception(_LE('in fixed duration looping call'))
                done.send_exception(*sys.exc_info())
                return
            else:
                done.send(True)

        self.done = done

        greenthread.spawn_n(_inner)
        return self.done


class DynamicLoopingCall(LoopingCallBase):
    """A looping call which sleeps until the next known event.

    The function called should return how long to sleep for before being
    called again.
    """

    def start(self, initial_delay=None, periodic_interval_max=None):
        self._running = True
        done = event.Event()

        def _inner():
            if initial_delay:
                greenthread.sleep(initial_delay)

            try:
                while self._running:
                    idle = self.f(*self.args, **self.kw)
                    if not self._running:
                        break

                    if periodic_interval_max is not None:
                        idle = min(idle, periodic_interval_max)
                    LOG.debug('Dynamic looping call %(func_name)r sleeping '
                              'for %(idle).02f seconds',
                              {'func_name': self.f, 'idle': idle})
                    greenthread.sleep(idle)
            except LoopingCallDone as e:
                self.stop()
                done.send(e.retvalue)
            except Exception:
                LOG.exception(_LE('in dynamic looping call'))
                done.send_exception(*sys.exc_info())
                return
            else:
                done.send(True)

        self.done = done

        greenthread.spawn(_inner)
        return self.done