annotate roundup/anypy/random_.py @ 6565:2c2dbfc332ba

Try to handle multiple connections better. The session database is a hot spot. When multiple requests (e.g. 20) come in at the same time session database contention can get great. The original code didn't retry session database access when the open failed. This resulted in errors at the client. The second pass delayed 0.01 seconds and retried. It was better but we still had multiple second stalls. I think the first request got in, everybody else backed up and then retried at the same time. Again they stepped on each other. With logging I would see many counters go all the way to low single digits or to -1 indicating falure. This pass uses randomint to generate delays from 0-.125 seconds in 5ms increments. This performs better in testing. I rarely saw a counter less than 13 (2 failed retries). Current logging starts after 6 failures and counts down until success or failure.
author John Rouillard <rouilj@ieee.org>
date Thu, 16 Dec 2021 20:02:00 -0500
parents adf54478cdaf
children 07ce4e4110f5
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1 try:
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2 from secrets import choice, randbelow, token_bytes
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3
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4 def seed(v=None):
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5 pass
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7 is_weak = False
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8 except ImportError:
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9 import os as _os
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10 import random as _random
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12 # prefer to use SystemRandom if it is available
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13 if hasattr(_random, 'SystemRandom'):
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14 def seed(v=None):
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15 pass
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17 _r = _random.SystemRandom()
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18 is_weak = False
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19 else:
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20 # don't completely throw away the existing state, but add some
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21 # more random state to the existing state
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22 def seed(v=None):
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23 import os, time
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24 _r.seed((_r.getstate(),
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25 v,
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26 hasattr(os, 'getpid') and os.getpid(),
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27 time.time()))
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29 # create our own instance so we don't mess with the global
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30 # random number generator
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31 _r = _random.Random()
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32 seed()
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33 is_weak = True
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34
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35 choice = _r.choice
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36
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37 def randbelow(i):
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38 return _r.randint(0, i - 1)
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39
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40 if hasattr(_os, 'urandom'):
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41 def token_bytes(l):
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42 return _os.urandom(l)
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43 else:
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44 def token_bytes(l):
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45 _bchr = chr if str == bytes else lambda x: bytes((x,))
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46 return b''.join([_bchr(_r.getrandbits(8)) for i in range(l)])

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