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1# Copyright 2017 The Chromium OS Authors. All rights reserved.
2# Use of this source code is governed by a BSD-style license that can be
3# found in the LICENSE file.
4
5from __future__ import absolute_import
6from __future__ import print_function
7
8import logging
9
10import common
11from autotest_lib.server.hosts import host_info
12from chromite.lib import metrics
13
14
15_METRICS_PREFIX = 'chromeos/autotest/autoserv/host_info/shadowing_store/'
16_REFRESH_METRIC_NAME = _METRICS_PREFIX + 'refresh_count'
17_COMMIT_METRIC_NAME = _METRICS_PREFIX + 'commit_count'
18
19
20logger = logging.getLogger(__file__)
21
22class ShadowingStore(host_info.CachingHostInfoStore):
23    """A composite CachingHostInfoStore that maintains a main and shadow store.
24
25    ShadowingStore accepts two CachingHostInfoStore objects - primary_store and
26    shadow_store. All refresh/commit operations are serviced through
27    primary_store.  In addition, shadow_store is updated and compared with this
28    information, leaving breadcrumbs when the two differ. Any errors in
29    shadow_store operations are logged and ignored so as to not affect the user.
30
31    This is a transitional CachingHostInfoStore that allows us to continue to
32    use an AfeStore in practice, but also create a backing FileStore so that we
33    can validate the use of FileStore in prod.
34    """
35
36    def __init__(self, primary_store, shadow_store,
37                 mismatch_callback=None):
38        """
39        @param primary_store: A CachingHostInfoStore to be used as the primary
40                store.
41        @param shadow_store: A CachingHostInfoStore to be used to shadow the
42                primary store.
43        @param mismatch_callback: A callback used to notify whenever we notice a
44                mismatch between primary_store and shadow_store. The signature
45                of the callback must match:
46                    callback(primary_info, shadow_info)
47                where primary_info and shadow_info are HostInfo objects obtained
48                from the two stores respectively.
49                Mostly used by unittests. Actual users don't know / nor care
50                that they're using a ShadowingStore.
51        """
52        super(ShadowingStore, self).__init__()
53        self._primary_store = primary_store
54        self._shadow_store = shadow_store
55        self._mismatch_callback = (
56                mismatch_callback if mismatch_callback is not None
57                else _log_info_mismatch)
58        try:
59            self._shadow_store.commit(self._primary_store.get())
60        except host_info.StoreError as e:
61            metrics.Counter(
62                    _METRICS_PREFIX + 'initialization_fail_count').increment()
63            logger.exception(
64                    'Failed to initialize shadow store. '
65                    'Expect primary / shadow desync in the future.')
66
67    def __str__(self):
68        return '%s[%s, %s]' % (type(self).__name__, self._primary_store,
69                               self._shadow_store)
70
71    def _refresh_impl(self):
72        """Obtains HostInfo from the primary and compares against shadow"""
73        primary_info = self._refresh_from_primary_store()
74        try:
75            shadow_info = self._refresh_from_shadow_store()
76        except host_info.StoreError:
77            logger.exception('Shadow refresh failed. '
78                             'Skipping comparison with primary.')
79            return primary_info
80        self._verify_store_infos(primary_info, shadow_info)
81        return primary_info
82
83    def _commit_impl(self, info):
84        """Commits HostInfo to both the primary and shadow store"""
85        self._commit_to_primary_store(info)
86        self._commit_to_shadow_store(info)
87
88    def _commit_to_primary_store(self, info):
89        try:
90            self._primary_store.commit(info)
91        except host_info.StoreError:
92            metrics.Counter(_COMMIT_METRIC_NAME).increment(
93                    fields={'file_commit_result': 'skipped'})
94            raise
95
96    def _commit_to_shadow_store(self, info):
97        try:
98            self._shadow_store.commit(info)
99        except host_info.StoreError:
100            logger.exception(
101                    'shadow commit failed. '
102                    'Expect primary / shadow desync in the future.')
103            metrics.Counter(_COMMIT_METRIC_NAME).increment(
104                    fields={'file_commit_result': 'fail'})
105        else:
106            metrics.Counter(_COMMIT_METRIC_NAME).increment(
107                    fields={'file_commit_result': 'success'})
108
109    def _refresh_from_primary_store(self):
110        try:
111            return self._primary_store.get(force_refresh=True)
112        except host_info.StoreError:
113            metrics.Counter(_REFRESH_METRIC_NAME).increment(
114                    fields={'validation_result': 'skipped'})
115            raise
116
117    def _refresh_from_shadow_store(self):
118        try:
119            return self._shadow_store.get(force_refresh=True)
120        except host_info.StoreError:
121            metrics.Counter(_REFRESH_METRIC_NAME).increment(fields={
122                    'validation_result': 'fail_shadow_store_refresh'})
123            raise
124
125    def _verify_store_infos(self, primary_info, shadow_info):
126        if primary_info == shadow_info:
127            metrics.Counter(_REFRESH_METRIC_NAME).increment(
128                    fields={'validation_result': 'success'})
129        else:
130            self._mismatch_callback(primary_info, shadow_info)
131            metrics.Counter(_REFRESH_METRIC_NAME).increment(
132                    fields={'validation_result': 'fail_mismatch'})
133            self._shadow_store.commit(primary_info)
134
135
136def _log_info_mismatch(primary_info, shadow_info):
137    """Log the two HostInfo instances.
138
139    Used as the default mismatch_callback.
140    """
141    logger.warning('primary / shadow disagree on refresh.')
142    logger.warning('primary: %s', primary_info)
143    logger.warning('shadow: %s', shadow_info)
144