Merge pull request #8 from MichaelRazum/master

Added RecalculationNeeded Exception

cachier/core.py

@@ -30,7 +30,7 @@ except ImportError:  # we're in python 2.x
     from concurrent.futures import ThreadPoolExecutor
 
 from .pickle_core import _PickleCore
-from .mongo_core import _MongoCore
+from .mongo_core import _MongoCore, RecalculationNeeded
 
 
 
@@ -82,8 +82,6 @@ def _calc_entry(core, key, func, args, kwds):
     finally:
         core.mark_entry_not_calculated(key)
 
-
-
 def cachier(stale_after=None, next_time=False, pickle_reload=True,
             mongetter=None):
     """A persistent, stale-free memoization decorator.
@@ -156,7 +154,10 @@ def cachier(stale_after=None, next_time=False, pickle_reload=True,
                                     _print('Returning stale.')
                                     return entry['value']  # return stale val
                                 _print('Already calc. Waiting on change.')
-                                return core.wait_on_entry_calc(key)
+                                try:
+                                    return core.wait_on_entry_calc(key)
+                                except RecalculationNeeded:
+                                    return _calc_entry(core, key, func, args, kwds)
                             if next_time:
                                 _print('Async calc and return stale')
                                 try:
@@ -173,7 +174,10 @@ def cachier(stale_after=None, next_time=False, pickle_reload=True,
                     return entry['value']
                 if entry['being_calculated']:
                     _print('No value but being calculated. Waiting.')
-                    return core.wait_on_entry_calc(key)
+                    try:
+                        return core.wait_on_entry_calc(key)
+                    except RecalculationNeeded:
+                        return _calc_entry(core, key, func, args, kwds)
             _print('No entry found. No current calc. Calling like a boss.')
             return _calc_entry(core, key, func, args, kwds)
 

cachier/mongo_core.py

@@ -28,6 +28,8 @@ from .base_core import _BaseCore
 
 MONGO_SLEEP_DURATION_IN_SEC = 1
 
+class RecalculationNeeded(Exception):
+    pass
 
 class _MongoCore(_BaseCore):
 
@@ -126,6 +128,8 @@ class _MongoCore(_BaseCore):
         while True:
             time.sleep(MONGO_SLEEP_DURATION_IN_SEC)
             key, entry = self.get_entry_by_key(key)
+            if entry is None:
+                raise RecalculationNeeded()
             if entry is not None and not entry['being_calculated']:
                 return entry['value']
 

tests/test_mongo_core.py

@@ -1,5 +1,6 @@
 """Testing the MongoDB core of cachier."""
 
+import datetime
 import sys
 from random import random
 from datetime import timedelta
@@ -15,8 +16,7 @@ from pymongo.mongo_client import MongoClient
 from pymongo.errors import OperationFailure
 
 from cachier import cachier
-from cachier.mongo_core import _MongoCore
-
+from cachier.mongo_core import _MongoCore, RecalculationNeeded
 
 _TEST_HOST = 'ds119508.mlab.com'
 _TEST_PORT = 19508
@@ -163,3 +163,43 @@ def test_mongo_write_failure():
 def test_mongo_clear_being_calculated():
     """Testing MongoDB core clear_being_calculated."""
     _func_w_bad_mongo.clear_being_calculated()
+
+
+def test_stalled_mongo_db_cache():
+    @cachier(mongetter=_test_mongetter)
+    def _stalled_func():
+        return 1
+    core = _MongoCore(_test_mongetter, None, False)
+    core.set_func(_stalled_func)
+    core.clear_cache()
+    with pytest.raises(RecalculationNeeded):
+        core.wait_on_entry_calc(key=None)
+
+def test_stalled_mong_db_core(monkeypatch):
+    def mock_get_entry(self, args, kwargs):
+        return "key", {'being_calculated': True}
+    def mock_get_entry_by_key(self, key):
+        return "key", None
+    monkeypatch.setattr("cachier.mongo_core._MongoCore.get_entry", mock_get_entry )
+    monkeypatch.setattr("cachier.mongo_core._MongoCore.get_entry_by_key", mock_get_entry_by_key )
+    @cachier(mongetter=_test_mongetter)
+    def _stalled_func():
+        return 1
+    res = _stalled_func()
+    assert res == 1
+
+    def mock_get_entry_2(self, args, kwargs):
+        return "key", {'being_calculated': True,
+                       "value": 1,
+                       "time": datetime.datetime.now() - datetime.timedelta(seconds=10)}
+    monkeypatch.setattr("cachier.mongo_core._MongoCore.get_entry", mock_get_entry_2 )
+
+    stale_after = datetime.timedelta(seconds=1)
+    @cachier(mongetter=_test_mongetter,stale_after=stale_after)
+    def _stalled_func_2():
+        """ Testing stalled function"""
+        return 2
+    res = _stalled_func_2()
+    assert res == 2
+
+