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from botocore.exceptions import CapacityNotAvailableError
from botocore.retries import bucket
from tests import unittest
class FakeClock(bucket.Clock):
def __init__(self, timestamp_sequences):
self.timestamp_sequences = timestamp_sequences
self.sleep_call_amounts = []
def sleep(self, amount):
self.sleep_call_amounts.append(amount)
def current_time(self):
return self.timestamp_sequences.pop(0)
class TestTokenBucket(unittest.TestCase):
def setUp(self):
self.timestamp_sequences = [0]
self.clock = FakeClock(self.timestamp_sequences)
def create_token_bucket(self, max_rate=10, min_rate=0.1):
return bucket.TokenBucket(
max_rate=max_rate, clock=self.clock, min_rate=min_rate
)
def test_can_acquire_amount(self):
self.timestamp_sequences.extend(
[
# Requests tokens every second, which is well below our
# 10 TPS fill rate.
1,
2,
3,
4,
5,
]
)
token_bucket = self.create_token_bucket(max_rate=10)
for _ in range(5):
self.assertTrue(token_bucket.acquire(1, block=False))
def test_can_change_max_capacity_lower(self):
# Requests at 1 TPS.
self.timestamp_sequences.extend([1, 2, 3, 4, 5])
token_bucket = self.create_token_bucket(max_rate=10)
# Request the first 5 tokens with max_rate=10
for _ in range(5):
self.assertTrue(token_bucket.acquire(1, block=False))
# Now scale the max_rate down to 1 on the 5th second.
self.timestamp_sequences.append(5)
token_bucket.max_rate = 1
# And then from seconds 6-10 we request at one per second.
self.timestamp_sequences.extend([6, 7, 8, 9, 10])
for _ in range(5):
self.assertTrue(token_bucket.acquire(1, block=False))
def test_max_capacity_is_at_least_one(self):
token_bucket = self.create_token_bucket()
self.timestamp_sequences.append(1)
token_bucket.max_rate = 0.5
self.assertEqual(token_bucket.max_rate, 0.5)
self.assertEqual(token_bucket.max_capacity, 1)
def test_acquire_fails_on_non_block_mode_returns_false(self):
self.timestamp_sequences.extend(
[
# Initial creation time.
0,
# Requests a token 1 second later.
1,
]
)
token_bucket = self.create_token_bucket(max_rate=10)
with self.assertRaises(CapacityNotAvailableError):
token_bucket.acquire(100, block=False)
def test_can_retrieve_at_max_send_rate(self):
self.timestamp_sequences.extend(
[
# Request a new token every 100ms (10 TPS) for 2 seconds.
1 + 0.1 * i
for i in range(20)
]
)
token_bucket = self.create_token_bucket(max_rate=10)
for _ in range(20):
self.assertTrue(token_bucket.acquire(1, block=False))
def test_acquiring_blocks_when_capacity_reached(self):
# This is 1 token every 0.1 seconds.
token_bucket = self.create_token_bucket(max_rate=10)
self.timestamp_sequences.extend(
[
# The first acquire() happens after .1 seconds.
0.1,
# The second acquire() will fail because we get tokens at
# 1 per 0.1 seconds. We will then sleep for 0.05 seconds until we
# get a new token.
0.15,
# And at 0.2 seconds we get our token.
0.2,
# And at 0.3 seconds we have no issues getting a token.
# Because we're using such small units (to avoid bloating the
# test run time), we have to go slightly over 0.3 seconds here.
0.300001,
]
)
self.assertTrue(token_bucket.acquire(1, block=False))
self.assertEqual(token_bucket.available_capacity, 0)
self.assertTrue(token_bucket.acquire(1, block=True))
self.assertEqual(token_bucket.available_capacity, 0)
self.assertTrue(token_bucket.acquire(1, block=False))
def test_rate_cant_go_below_min(self):
token_bucket = self.create_token_bucket(max_rate=1, min_rate=0.2)
self.timestamp_sequences.append(1)
token_bucket.max_rate = 0.1
self.assertEqual(token_bucket.max_rate, 0.2)
self.assertEqual(token_bucket.max_capacity, 1)
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