Add optional semaphore to protect integrity of persistent storage backend
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lash
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21D2E7BB88C2A746
@ -1,3 +1,5 @@
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- 0.2.4
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* Add optional concurrency lock for persistence store, implemented for file store
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- 0.2.3
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* Add noop-store, for convenience for code using persist constructor but will only use memory state
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- 0.2.2
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@ -1,6 +1,6 @@
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[metadata]
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name = shep
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version = 0.2.3
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version = 0.2.4
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description = Multi-state key stores using bit masks
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author = Louis Holbrook
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author_email = dev@holbrook.no
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@ -22,7 +22,7 @@ licence_files =
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[options]
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include_package_data = True
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python_requires = >= 3.6
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python_requires = >= 3.7
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packages =
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shep
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shep.store
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@ -32,3 +32,9 @@ class StateTransitionInvalid(Exception):
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"""Raised if state transition verification fails
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"""
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pass
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class StateLockedKey(Exception):
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"""Attempt to write to a state key that is being written to by another client
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"""
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pass
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@ -3,7 +3,10 @@ import datetime
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# local imports
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from .state import State
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from .error import StateItemExists
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from .error import (
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StateItemExists,
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StateLockedKey,
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)
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class PersistedState(State):
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@ -34,13 +37,14 @@ class PersistedState(State):
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See shep.state.State.put
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"""
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to_state = super(PersistedState, self).put(key, state=state, contents=contents)
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k = self.name(to_state)
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k = self.to_name(state)
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self.__ensure_store(k)
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self.__stores[k].put(key, contents)
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super(PersistedState, self).put(key, state=state, contents=contents)
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self.register_modify(key)
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@ -56,9 +60,14 @@ class PersistedState(State):
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k_to = self.name(to_state)
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self.__ensure_store(k_to)
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contents = None
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try:
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contents = self.__stores[k_from].get(key)
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self.__stores[k_to].put(key, contents)
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self.__stores[k_from].remove(key)
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except StateLockedKey as e:
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super(PersistedState, self).unset(key, or_state, allow_base=True)
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raise e
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self.sync(to_state)
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@ -143,6 +152,7 @@ class PersistedState(State):
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:raises StateItemExists: A content key is already recorded with a different state in memory than in persisted store.
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# :todo: if sync state is none, sync all
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"""
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states = []
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if state == None:
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states = list(self.all())
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@ -208,10 +218,11 @@ class PersistedState(State):
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See shep.state.State.replace
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"""
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super(PersistedState, self).replace(key, contents)
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state = self.state(key)
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k = self.name(state)
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return self.__stores[k].replace(key, contents)
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r = self.__stores[k].replace(key, contents)
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super(PersistedState, self).replace(key, contents)
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return r
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def modified(self, key):
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@ -185,6 +185,12 @@ class State:
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self.__set(k, v)
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def to_name(self, k):
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if k == None:
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k = 0
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return self.name(k)
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def __alias(self, k, *args):
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v = 0
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for a in args:
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@ -436,7 +442,7 @@ class State:
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return self.__move(key, current_state, to_state)
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def unset(self, key, not_state):
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def unset(self, key, not_state, allow_base=False):
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"""Unset a single bit, moving to a pure or alias state.
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The resulting state cannot be State.base_state_name (0).
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@ -462,7 +468,7 @@ class State:
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if to_state == current_state:
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raise ValueError('invalid change for state {}: {}'.format(key, not_state))
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if to_state == getattr(self, self.base_state_name):
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if to_state == getattr(self, self.base_state_name) and not allow_base:
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raise ValueError('State {} for {} cannot be reverted to {}'.format(current_state, key, self.base_state_name))
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new_state = self.__reverse.get(to_state)
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@ -7,6 +7,7 @@ from .base import (
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re_processedname,
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StoreFactory,
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)
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from shep.error import StateLockedKey
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class SimpleFileStore:
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@ -15,13 +16,45 @@ class SimpleFileStore:
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:param path: Filesystem base path for all state directory
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:type path: str
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"""
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def __init__(self, path, binary=False):
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def __init__(self, path, binary=False, lock_path=None):
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self.__path = path
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os.makedirs(self.__path, exist_ok=True)
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if binary:
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self.__m = ['rb', 'wb']
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else:
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self.__m = ['r', 'w']
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self.__lock_path = lock_path
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if self.__lock_path != None:
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os.makedirs(lock_path, exist_ok=True)
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def __is_locked(self, k):
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if self.__lock_path == None:
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return False
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for v in os.listdir(self.__lock_path):
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if k == v:
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return True
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return False
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def __lock(self, k):
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if self.__lock_path == None:
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return
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if self.__is_locked(k):
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raise StateLockedKey(k)
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fp = os.path.join(self.__lock_path, k)
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f = open(fp, 'w')
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f.close()
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def __unlock(self, k):
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if self.__lock_path == None:
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return
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fp = os.path.join(self.__lock_path, k)
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try:
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os.unlink(fp)
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except FileNotFoundError:
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pass
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def put(self, k, contents=None):
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@ -32,6 +65,7 @@ class SimpleFileStore:
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:param contents: Optional contents to assign for content key
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:type contents: any
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"""
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self.__lock(k)
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fp = os.path.join(self.__path, k)
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if contents == None:
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if self.__m[1] == 'wb':
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@ -42,6 +76,7 @@ class SimpleFileStore:
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f = open(fp, self.__m[1])
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f.write(contents)
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f.close()
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self.__unlock(k)
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def remove(self, k):
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@ -51,8 +86,10 @@ class SimpleFileStore:
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:type k: str
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:raises FileNotFoundError: Content key does not exist in the state
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"""
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self.__lock(k)
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fp = os.path.join(self.__path, k)
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os.unlink(fp)
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self.__unlock(k)
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def get(self, k):
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@ -64,10 +101,12 @@ class SimpleFileStore:
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:rtype: any
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:return: Contents
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"""
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self.__lock(k)
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fp = os.path.join(self.__path, k)
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f = open(fp, self.__m[0])
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r = f.read()
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f.close()
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self.__unlock(k)
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return r
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@ -77,6 +116,7 @@ class SimpleFileStore:
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:rtype: list of str
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:return: Content keys in state
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"""
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self.__lock('.list')
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files = []
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for p in os.listdir(self.__path):
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fp = os.path.join(self.__path, p)
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@ -86,6 +126,7 @@ class SimpleFileStore:
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if len(r) == 0:
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r = None
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files.append((p, r,))
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self.__unlock('.list')
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return files
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@ -110,16 +151,20 @@ class SimpleFileStore:
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:param contents: Contents
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:type contents: any
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"""
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self.__lock(k)
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fp = os.path.join(self.__path, k)
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os.stat(fp)
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f = open(fp, self.__m[1])
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r = f.write(contents)
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f.close()
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self.__unlock(k)
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def modified(self, k):
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self.__lock(k)
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path = self.path(k)
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st = os.stat(path)
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self.__unlock(k)
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return st.st_ctime
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@ -133,9 +178,10 @@ class SimpleFileStoreFactory(StoreFactory):
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:param path: Filesystem path as base path for states
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:type path: str
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"""
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def __init__(self, path, binary=False):
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def __init__(self, path, binary=False, use_lock=False):
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self.__path = path
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self.__binary = binary
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self.__use_lock = use_lock
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def add(self, k):
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@ -146,9 +192,13 @@ class SimpleFileStoreFactory(StoreFactory):
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:rtype: SimpleFileStore
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:return: A filesystem persistence instance with the given identifier as subdirectory
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"""
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lock_path = None
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if self.__use_lock:
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lock_path = os.path.join(self.__path, '.lock')
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k = str(k)
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store_path = os.path.join(self.__path, k)
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return SimpleFileStore(store_path, binary=self.__binary)
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return SimpleFileStore(store_path, binary=self.__binary, lock_path=lock_path)
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def ls(self):
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@ -11,6 +11,7 @@ from shep.error import (
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StateExists,
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StateInvalid,
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StateItemExists,
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StateLockedKey,
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)
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@ -257,5 +258,52 @@ class TestFileStore(unittest.TestCase):
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self.assertEqual(len(r), 3)
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def test_lock(self):
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factory = SimpleFileStoreFactory(self.d, use_lock=True)
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states = PersistedState(factory.add, 3)
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states.add('foo')
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states.add('bar')
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states.add('baz')
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states.alias('xyzzy', states.FOO | states.BAR)
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states.alias('plugh', states.FOO | states.BAR | states.BAZ)
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states.put('abcd')
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lock_path = os.path.join(self.d, '.lock')
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os.stat(lock_path)
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fp = os.path.join(self.d, '.lock', 'xxxx')
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f = open(fp, 'w')
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f.close()
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with self.assertRaises(StateLockedKey):
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states.put('xxxx')
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os.unlink(fp)
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states.put('xxxx')
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states.set('xxxx', states.FOO)
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states.set('xxxx', states.BAR)
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states.replace('xxxx', contents='zzzz')
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fp = os.path.join(self.d, '.lock', 'xxxx')
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f = open(fp, 'w')
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f.close()
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with self.assertRaises(StateLockedKey):
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states.set('xxxx', states.BAZ)
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v = states.state('xxxx')
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self.assertEqual(v, states.XYZZY)
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with self.assertRaises(StateLockedKey):
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states.unset('xxxx', states.FOO)
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with self.assertRaises(StateLockedKey):
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states.replace('xxxx', contents='yyyy')
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v = states.get('xxxx')
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self.assertEqual(v, 'zzzz')
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if __name__ == '__main__':
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unittest.main()
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