125 lines
4.1 KiB
Python
125 lines
4.1 KiB
Python
#!/usr/bin/env python
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# This module creates a list of cron intervals for a node in a group of nodes
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# to ensure each node runs a cron in round robbin style.
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from __future__ import print_function
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import argparse
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import json
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import sys
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MINUTE_SPAN = 1
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HOUR_SPAN = 60
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DAY_SPAN = 24 * HOUR_SPAN
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WEEK_SPAN = 7 * DAY_SPAN
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class RotationIntervalTooLong(Exception):
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pass
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def json_exit(msg=None, failed=False, changed=False):
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if type(msg) is not dict:
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msg = {'msg': str(msg)}
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msg.update({'failed': failed, 'changed': changed})
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print(json.dumps(msg))
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sys.exit()
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def generate(host_index, total_hosts, total_rotation_mins):
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min = '*' # 0-59
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hour = '*' # 0-23
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day = '*' # 0-6 (day of week)
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crons = []
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if host_index >= total_hosts:
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return crons
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# We need to rotate the key every total_rotation_mins minutes.
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# When there are N hosts, each host should rotate once every N *
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# total_rotation_mins minutes, in a round-robin manner.
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# We can generate a cycle for index 0, then add an offset specific to each
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# host.
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# NOTE: Minor under-rotation is better than over-rotation since tokens
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# may become invalid if keys are over-rotated.
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host_rotation_mins = total_rotation_mins * total_hosts
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host_rotation_offset = total_rotation_mins * host_index
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# Can't currently rotate less than once per week.
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if total_rotation_mins > WEEK_SPAN:
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msg = ("Unable to schedule fernet key rotation with an interval "
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"greater than 1 week divided by the number of hosts")
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raise RotationIntervalTooLong(msg)
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# Build crons multiple of a day
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elif host_rotation_mins > DAY_SPAN:
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time = host_rotation_offset
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while time + total_rotation_mins <= WEEK_SPAN:
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day = time // DAY_SPAN
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hour = time % HOUR_SPAN
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min = time % HOUR_SPAN
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crons.append({'min': min, 'hour': hour, 'day': day})
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time += host_rotation_mins
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# Build crons for multiple of an hour
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elif host_rotation_mins > HOUR_SPAN:
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time = host_rotation_offset
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while time + total_rotation_mins <= DAY_SPAN:
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hour = time // HOUR_SPAN
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min = time % HOUR_SPAN
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crons.append({'min': min, 'hour': hour, 'day': day})
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time += host_rotation_mins
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# Build crons for multiple of a minute
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else:
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time = host_rotation_offset
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while time + total_rotation_mins <= HOUR_SPAN:
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min = time // MINUTE_SPAN
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crons.append({'min': min, 'hour': hour, 'day': day})
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time += host_rotation_mins
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return crons
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def main():
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parser = argparse.ArgumentParser(description='''Creates a list of cron
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intervals for a node in a group of nodes to ensure each node runs
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a cron in round robin style.''')
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parser.add_argument('-t', '--time',
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help='Time in minutes for a key rotation cycle',
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required=True,
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type=int)
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parser.add_argument('-i', '--index',
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help='Index of host starting from 0',
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required=True,
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type=int)
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parser.add_argument('-n', '--number',
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help='Number of hosts',
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required=True,
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type=int)
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args = parser.parse_args()
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try:
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jobs = generate(args.index, args.number, args.time)
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except Exception as e:
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json_exit(str(e), failed=True)
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json_exit({'cron_jobs': jobs})
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if __name__ == "__main__":
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main()
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