/usr/lib/python3/dist-packages/pymongo/max_staleness_selectors.py is in python3-pymongo 3.4.0-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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 | # Copyright 2016 MongoDB, Inc.
#
# 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.
"""Criteria to select ServerDescriptions based on maxStalenessSeconds.
The Max Staleness Spec says: When there is a known primary P,
a secondary S's staleness is estimated with this formula:
(S.lastUpdateTime - S.lastWriteDate) - (P.lastUpdateTime - P.lastWriteDate)
+ heartbeatFrequencyMS
When there is no known primary, a secondary S's staleness is estimated with:
SMax.lastWriteDate - S.lastWriteDate + heartbeatFrequencyMS
where "SMax" is the secondary with the greatest lastWriteDate.
"""
from pymongo.errors import ConfigurationError
from pymongo.server_type import SERVER_TYPE
# Constant defined in Max Staleness Spec: An idle primary writes a no-op every
# 10 seconds to refresh secondaries' lastWriteDate values.
IDLE_WRITE_PERIOD = 10
SMALLEST_MAX_STALENESS = 90
def _validate_max_staleness(max_staleness,
heartbeat_frequency):
# We checked for max staleness -1 before this, it must be positive here.
if max_staleness < heartbeat_frequency + IDLE_WRITE_PERIOD:
raise ConfigurationError(
"maxStalenessSeconds must be at least heartbeatFrequencyMS +"
" %d seconds. maxStalenessSeconds is set to %d,"
" heartbeatFrequencyMS is set to %d." % (
IDLE_WRITE_PERIOD, max_staleness, heartbeat_frequency * 1000))
if max_staleness < SMALLEST_MAX_STALENESS:
raise ConfigurationError(
"maxStalenessSeconds must be at least %d. "
"maxStalenessSeconds is set to %d." % (
SMALLEST_MAX_STALENESS, max_staleness))
def _with_primary(max_staleness, selection):
"""Apply max_staleness, in seconds, to a Selection with a known primary."""
primary = selection.primary
sds = []
for s in selection.server_descriptions:
if s.server_type == SERVER_TYPE.RSSecondary:
# See max-staleness.rst for explanation of this formula.
staleness = (
(s.last_update_time - s.last_write_date) -
(primary.last_update_time - primary.last_write_date) +
selection.heartbeat_frequency)
if staleness <= max_staleness:
sds.append(s)
else:
sds.append(s)
return selection.with_server_descriptions(sds)
def _no_primary(max_staleness, selection):
"""Apply max_staleness, in seconds, to a Selection with no known primary."""
# Secondary that's replicated the most recent writes.
smax = selection.secondary_with_max_last_write_date()
if not smax:
# No secondaries and no primary, short-circuit out of here.
return selection.with_server_descriptions([])
sds = []
for s in selection.server_descriptions:
if s.server_type == SERVER_TYPE.RSSecondary:
# See max-staleness.rst for explanation of this formula.
staleness = (smax.last_write_date -
s.last_write_date +
selection.heartbeat_frequency)
if staleness <= max_staleness:
sds.append(s)
else:
sds.append(s)
return selection.with_server_descriptions(sds)
def select(max_staleness, selection):
"""Apply max_staleness, in seconds, to a Selection."""
if max_staleness == -1:
return selection
# Server Selection Spec: If the TopologyType is ReplicaSetWithPrimary or
# ReplicaSetNoPrimary, a client MUST raise an error if maxStaleness <
# heartbeatFrequency + IDLE_WRITE_PERIOD, or if maxStaleness < 90.
_validate_max_staleness(max_staleness, selection.heartbeat_frequency)
if selection.primary:
return _with_primary(max_staleness, selection)
else:
return _no_primary(max_staleness, selection)
|