mirror of
https://github.com/wassname/catalyst.git
synced 2026-06-28 00:58:26 +08:00
Eddie Hebert
76e14eda2f
Add a cache interface which supports expirable entries with a changeable
backend for the cache into which they are entered.
The default cache is a `dict` but could swapped for
`cachetools.LRUCache` or any other cache which supports `__get__`,
`__set__`, and `__del__`.
So that consumers can change the use of `CachedObjects` stored in a
cache from:
```
self._cache = {}
...
try:
obj = self._cache[key]
try:
return obj.unwrap(dt)
except Expired:
pass
except KeyError:
pass
...
self._cache[key] = CachedObject(value, new_expiration)
```
to:
```
self._cache = ExpiringCache(LRUCache(maxsize=6))
...
try:
return self._cache.get(key, dt)
except KeyError:
# Get fresh value
...
self._cache.set(key, value, new_expiration)
```
61 lines
1.9 KiB
Python
61 lines
1.9 KiB
Python
from unittest import TestCase
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from pandas import Timestamp, Timedelta
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from zipline.utils.cache import CachedObject, Expired, ExpiringCache
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class CachedObjectTestCase(TestCase):
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def test_cached_object(self):
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expiry = Timestamp('2014')
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before = expiry - Timedelta('1 minute')
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after = expiry + Timedelta('1 minute')
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obj = CachedObject(1, expiry)
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self.assertEqual(obj.unwrap(before), 1)
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self.assertEqual(obj.unwrap(expiry), 1) # Unwrap on expiry is allowed.
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with self.assertRaises(Expired) as e:
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obj.unwrap(after)
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self.assertEqual(e.exception.args, (expiry,))
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class ExpiringCacheTestCase(TestCase):
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def test_expiring_cache(self):
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expiry_1 = Timestamp('2014')
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before_1 = expiry_1 - Timedelta('1 minute')
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after_1 = expiry_1 + Timedelta('1 minute')
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expiry_2 = Timestamp('2015')
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after_2 = expiry_1 + Timedelta('1 minute')
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expiry_3 = Timestamp('2016')
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cache = ExpiringCache()
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cache.set('foo', 1, expiry_1)
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cache.set('bar', 2, expiry_2)
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self.assertEqual(cache.get('foo', before_1), 1)
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# Unwrap on expiry is allowed.
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self.assertEqual(cache.get('foo', expiry_1), 1)
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with self.assertRaises(KeyError) as e:
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self.assertEqual(cache.get('foo', after_1))
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self.assertEqual(e.exception.args, ('foo',))
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# Should raise same KeyError after deletion.
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with self.assertRaises(KeyError) as e:
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self.assertEqual(cache.get('foo', before_1))
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self.assertEqual(e.exception.args, ('foo',))
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# Second value should still exist.
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self.assertEqual(cache.get('bar', after_2), 2)
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# Should raise similar KeyError on non-existent key.
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with self.assertRaises(KeyError) as e:
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self.assertEqual(cache.get('baz', expiry_3))
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self.assertEqual(e.exception.args, ('baz',))
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