OpenSlides/openslides/utils/cache_providers.py

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from collections import defaultdict
from typing import (
TYPE_CHECKING,
Any,
Dict,
Iterable,
List,
Optional,
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Set,
Tuple,
)
from django.apps import apps
from typing_extensions import Protocol
from .utils import split_element_id, str_dict_to_bytes
if TYPE_CHECKING:
# Dummy import Collection for mypy, can be fixed with python 3.7
from .collection import CollectionElement # noqa
try:
import aioredis
except ImportError:
no_redis_dependency = True
else:
no_redis_dependency = False
class ElementCacheProvider(Protocol):
"""
Base class for cache provider.
See RedisCacheProvider as reverence implementation.
"""
def __init__(self, *args: Any) -> None: ...
async def clear_cache(self) -> None: ...
async def reset_full_cache(self, data: Dict[str, str]) -> None: ...
async def data_exists(self, user_id: Optional[int] = None) -> bool: ...
async def add_elements(self, elements: List[str]) -> None: ...
async def del_elements(self, elements: List[str], user_id: Optional[int] = None) -> None: ...
async def add_changed_elements(self, default_change_id: int, element_ids: Iterable[str]) -> int: ...
async def get_all_data(self, user_id: Optional[int] = None) -> Dict[bytes, bytes]: ...
async def get_data_since(
self,
change_id: int,
user_id: Optional[int] = None,
max_change_id: int = -1) -> Tuple[Dict[str, List[bytes]], List[str]]: ...
async def get_element(self, element_id: str) -> Optional[bytes]: ...
async def del_restricted_data(self, user_id: int) -> None: ...
async def set_lock(self, lock_name: str) -> bool: ...
async def get_lock(self, lock_name: str) -> bool: ...
async def del_lock(self, lock_name: str) -> None: ...
async def get_change_id_user(self, user_id: int) -> Optional[int]: ...
async def update_restricted_data(self, user_id: int, data: Dict[str, str]) -> None: ...
async def get_current_change_id(self) -> List[Tuple[str, int]]: ...
async def get_lowest_change_id(self) -> Optional[int]: ...
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class RedisConnectionContextManager:
"""
Async context manager for connections
"""
# TODO: contextlib.asynccontextmanager can be used in python 3.7
def __init__(self, redis_address: str) -> None:
self.redis_address = redis_address
async def __aenter__(self) -> 'aioredis.RedisConnection':
self.conn = await aioredis.create_redis(self.redis_address)
return self.conn
async def __aexit__(self, exc_type: Any, exc: Any, tb: Any) -> None:
self.conn.close()
class RedisCacheProvider:
"""
Cache provider that loads and saves the data to redis.
"""
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redis_pool: Optional[aioredis.RedisConnection] = None
full_data_cache_key: str = 'full_data'
restricted_user_cache_key: str = 'restricted_data:{user_id}'
change_id_cache_key: str = 'change_id'
prefix: str = 'element_cache_'
def __init__(self, redis: str) -> None:
self.redis_address = redis
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def get_connection(self) -> RedisConnectionContextManager:
"""
Returns contextmanager for a redis connection.
"""
return RedisConnectionContextManager(self.redis_address)
def get_full_data_cache_key(self) -> str:
return "".join((self.prefix, self.full_data_cache_key))
def get_restricted_data_cache_key(self, user_id: int) -> str:
return "".join((self.prefix, self.restricted_user_cache_key.format(user_id=user_id)))
def get_change_id_cache_key(self) -> str:
return "".join((self.prefix, self.change_id_cache_key))
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async def clear_cache(self) -> None:
"""
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Deleted all cache entries created with this element cache.
"""
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async with self.get_connection() as redis:
await redis.eval("return redis.call('del', 'fake_key', unpack(redis.call('keys', ARGV[1])))", keys=[], args=["{}*".format(self.prefix)])
async def reset_full_cache(self, data: Dict[str, str]) -> None:
"""
Deletes the full_data_cache and write new data in it.
"""
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async with self.get_connection() as redis:
tr = redis.multi_exec()
tr.delete(self.get_full_data_cache_key())
tr.hmset_dict(self.get_full_data_cache_key(), data)
await tr.execute()
async def data_exists(self, user_id: Optional[int] = None) -> bool:
"""
Returns True, when there is data in the cache.
If user_id is None, the method tests for full_data. If user_id is an int, it tests
for the restricted_data_cache for the user with the user_id. 0 is for anonymous.
"""
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async with self.get_connection() as redis:
if user_id is None:
cache_key = self.get_full_data_cache_key()
else:
cache_key = self.get_restricted_data_cache_key(user_id)
return await redis.exists(cache_key)
async def add_elements(self, elements: List[str]) -> None:
"""
Add or change elements to the cache.
elements is a list with an even len. the odd values are the element_ids and the even
values are the elements. The elements have to be encoded, for example with json.
"""
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async with self.get_connection() as redis:
await redis.hmset(
self.get_full_data_cache_key(),
*elements)
async def del_elements(self, elements: List[str], user_id: Optional[int] = None) -> None:
"""
Deletes elements from the cache.
elements has to be a list of element_ids.
If user_id is None, the elements are deleted from the full_data cache. If user_id is an
int, the elements are deleted one restricted_data_cache. 0 is for anonymous.
"""
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async with self.get_connection() as redis:
if user_id is None:
cache_key = self.get_full_data_cache_key()
else:
cache_key = self.get_restricted_data_cache_key(user_id)
await redis.hdel(
cache_key,
*elements)
async def add_changed_elements(self, default_change_id: int, element_ids: Iterable[str]) -> int:
"""
Saves which elements are change with a change_id.
Generates and returns the change_id.
"""
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async with self.get_connection() as redis:
return int(await redis.eval(
lua_script_change_data,
keys=[self.get_change_id_cache_key()],
args=[default_change_id, *element_ids]
))
async def get_all_data(self, user_id: Optional[int] = None) -> Dict[bytes, bytes]:
"""
Returns all data from a cache.
if user_id is None, then the data is returned from the full_data_cache. If it is and
int, it is returned from a restricted_data_cache. 0 is for anonymous.
"""
if user_id is None:
cache_key = self.get_full_data_cache_key()
else:
cache_key = self.get_restricted_data_cache_key(user_id)
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async with self.get_connection() as redis:
return await redis.hgetall(cache_key)
async def get_element(self, element_id: str) -> Optional[bytes]:
"""
Returns one element from the full_data_cache.
Returns None, when the element does not exist.
"""
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async with self.get_connection() as redis:
return await redis.hget(
self.get_full_data_cache_key(),
element_id)
async def get_data_since(
self,
change_id: int,
user_id: Optional[int] = None,
max_change_id: int = -1) -> Tuple[Dict[str, List[bytes]], List[str]]:
"""
Returns all elements since a change_id.
The returend value is a two element tuple. The first value is a dict the elements where
the key is the collection_string and the value a list of (json-) encoded elements. The
second element is a list of element_ids, that have been deleted since the change_id.
if user_id is None, the full_data is returned. If user_id is an int, the restricted_data
for an user is used. 0 is for the anonymous user.
"""
changed_elements: Dict[str, List[bytes]] = defaultdict(list)
deleted_elements: List[str] = []
if user_id is None:
cache_key = self.get_full_data_cache_key()
else:
cache_key = self.get_restricted_data_cache_key(user_id)
# Convert max_change_id to a string. If its negative, use the string '+inf'
redis_max_change_id = "+inf" if max_change_id < 0 else str(max_change_id)
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async with self.get_connection() as redis:
# lua script that returns gets all element_ids from change_id_cache_key
# and then uses each element_id on full_data or restricted_data.
# It returns a list where the odd values are the change_id and the
# even values the element as json. The function wait_make_dict creates
# a python dict from the returned list.
elements: Dict[bytes, Optional[bytes]] = await aioredis.util.wait_make_dict(redis.eval(
"""
-- Get change ids of changed elements
local element_ids = redis.call('zrangebyscore', KEYS[1], ARGV[1], ARGV[2])
-- Save elements in array. Rotate element_id and element_json
local elements = {}
for _, element_id in pairs(element_ids) do
table.insert(elements, element_id)
table.insert(elements, redis.call('hget', KEYS[2], element_id))
end
return elements
""",
keys=[self.get_change_id_cache_key(), cache_key],
args=[change_id, redis_max_change_id]))
for element_id, element_json in elements.items():
if element_id.startswith(b'_config'):
# Ignore config values from the change_id cache key
continue
if element_json is None:
# The element is not in the cache. It has to be deleted.
deleted_elements.append(element_id.decode())
else:
collection_string, id = split_element_id(element_id)
changed_elements[collection_string].append(element_json)
return changed_elements, deleted_elements
async def del_restricted_data(self, user_id: int) -> None:
"""
Deletes all restricted_data for an user. 0 is for the anonymous user.
"""
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async with self.get_connection() as redis:
await redis.delete(self.get_restricted_data_cache_key(user_id))
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async def set_lock(self, lock_name: str) -> bool:
"""
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Tries to sets a lock.
Returns True when the lock could be set.
Returns False when the lock was already set.
"""
# TODO: Improve lock. See: https://redis.io/topics/distlock
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async with self.get_connection() as redis:
return await redis.setnx("{}lock_{}".format(self.prefix, lock_name), 1)
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async def get_lock(self, lock_name: str) -> bool:
"""
Returns True, when the lock for the restricted_data of an user is set. Else False.
"""
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async with self.get_connection() as redis:
return await redis.get("{}lock_{}".format(self.prefix, lock_name))
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async def del_lock(self, lock_name: str) -> None:
"""
Deletes the lock for the restricted_data of an user. Does nothing when the
lock is not set.
"""
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async with self.get_connection() as redis:
await redis.delete("{}lock_{}".format(self.prefix, lock_name))
async def get_change_id_user(self, user_id: int) -> Optional[int]:
"""
Get the change_id for the restricted_data of an user.
This is the change_id where the restricted_data was last calculated.
"""
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async with self.get_connection() as redis:
return await redis.hget(self.get_restricted_data_cache_key(user_id), '_config:change_id')
async def update_restricted_data(self, user_id: int, data: Dict[str, str]) -> None:
"""
Updates the restricted_data for an user.
data has to be a dict where the key is an element_id and the value the (json-) encoded
element.
"""
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async with self.get_connection() as redis:
await redis.hmset_dict(self.get_restricted_data_cache_key(user_id), data)
async def get_current_change_id(self) -> List[Tuple[str, int]]:
"""
Get the highest change_id from redis.
"""
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async with self.get_connection() as redis:
return await redis.zrevrangebyscore(
self.get_change_id_cache_key(),
withscores=True,
count=1,
offset=0)
async def get_lowest_change_id(self) -> Optional[int]:
"""
Get the lowest change_id from redis.
Returns None if lowest score does not exist.
"""
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async with self.get_connection() as redis:
return await redis.zscore(
self.get_change_id_cache_key(),
'_config:lowest_change_id')
class MemmoryCacheProvider:
"""
CacheProvider for the ElementCache that uses only the memory.
See the RedisCacheProvider for a description of the methods.
This provider supports only one process. It saves the data into the memory.
When you use different processes they will use diffrent data.
"""
def __init__(self, *args: Any, **kwargs: Any) -> None:
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self.set_data_dicts()
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def set_data_dicts(self) -> None:
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self.full_data: Dict[str, str] = {}
self.restricted_data: Dict[int, Dict[str, str]] = {}
self.change_id_data: Dict[int, Set[str]] = {}
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self.locks: Dict[str, str] = {}
async def clear_cache(self) -> None:
self.set_data_dicts()
async def reset_full_cache(self, data: Dict[str, str]) -> None:
self.full_data = data
async def data_exists(self, user_id: Optional[int] = None) -> bool:
if user_id is None:
cache_dict = self.full_data
else:
cache_dict = self.restricted_data.get(user_id, {})
return bool(cache_dict)
async def add_elements(self, elements: List[str]) -> None:
if len(elements) % 2:
raise ValueError("The argument elements of add_elements has to be a list with an even number of elements.")
for i in range(0, len(elements), 2):
self.full_data[elements[i]] = elements[i+1]
async def del_elements(self, elements: List[str], user_id: Optional[int] = None) -> None:
if user_id is None:
cache_dict = self.full_data
else:
cache_dict = self.restricted_data.get(user_id, {})
for element in elements:
try:
del cache_dict[element]
except KeyError:
pass
async def add_changed_elements(self, default_change_id: int, element_ids: Iterable[str]) -> int:
element_ids = list(element_ids)
try:
change_id = (await self.get_current_change_id())[0][1] + 1
except IndexError:
change_id = default_change_id
for element_id in element_ids:
if change_id in self.change_id_data:
self.change_id_data[change_id].add(element_id)
else:
self.change_id_data[change_id] = {element_id}
return change_id
async def get_all_data(self, user_id: Optional[int] = None) -> Dict[bytes, bytes]:
if user_id is None:
cache_dict = self.full_data
else:
cache_dict = self.restricted_data.get(user_id, {})
return str_dict_to_bytes(cache_dict)
async def get_element(self, element_id: str) -> Optional[bytes]:
value = self.full_data.get(element_id, None)
return value.encode() if value is not None else None
async def get_data_since(
self,
change_id: int,
user_id: Optional[int] = None,
max_change_id: int = -1) -> Tuple[Dict[str, List[bytes]], List[str]]:
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changed_elements: Dict[str, List[bytes]] = defaultdict(list)
deleted_elements: List[str] = []
if user_id is None:
cache_dict = self.full_data
else:
cache_dict = self.restricted_data.get(user_id, {})
for data_change_id, element_ids in self.change_id_data.items():
if data_change_id < change_id or (max_change_id > -1 and data_change_id > max_change_id):
continue
for element_id in element_ids:
element_json = cache_dict.get(element_id, None)
if element_json is None:
deleted_elements.append(element_id)
else:
collection_string, id = split_element_id(element_id)
changed_elements[collection_string].append(element_json.encode())
return changed_elements, deleted_elements
async def del_restricted_data(self, user_id: int) -> None:
try:
del self.restricted_data[user_id]
except KeyError:
pass
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async def set_lock(self, lock_name: str) -> bool:
if lock_name in self.locks:
return False
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self.locks[lock_name] = "1"
return True
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async def get_lock(self, lock_name: str) -> bool:
return lock_name in self.locks
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async def del_lock(self, lock_name: str) -> None:
try:
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del self.locks[lock_name]
except KeyError:
pass
async def get_change_id_user(self, user_id: int) -> Optional[int]:
data = self.restricted_data.get(user_id, {})
change_id = data.get('_config:change_id', None)
return int(change_id) if change_id is not None else None
async def update_restricted_data(self, user_id: int, data: Dict[str, str]) -> None:
redis_data = self.restricted_data.setdefault(user_id, {})
redis_data.update(data)
async def get_current_change_id(self) -> List[Tuple[str, int]]:
change_data = self.change_id_data
if change_data:
return [('no_usefull_value', max(change_data.keys()))]
return []
async def get_lowest_change_id(self) -> Optional[int]:
change_data = self.change_id_data
if change_data:
return min(change_data.keys())
return None
class Cachable(Protocol):
"""
A Cachable is an object that returns elements that can be cached.
It needs at least the methods defined here.
"""
def get_collection_string(self) -> str:
"""
Returns the string representing the name of the cachable.
"""
def get_elements(self) -> List[Dict[str, Any]]:
"""
Returns all elements of the cachable.
"""
def restrict_elements(
self,
user: Optional['CollectionElement'],
elements: List[Dict[str, Any]]) -> List[Dict[str, Any]]:
"""
Converts full_data to restricted_data.
elements can be an empty list, a list with some elements of the cachable or with all
elements of the cachable.
"""
def get_all_cachables() -> List[Cachable]:
"""
Returns all element of OpenSlides.
"""
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out: List[Cachable] = []
for app in apps.get_app_configs():
try:
# Get the method get_startup_elements() from an app.
# This method has to return an iterable of Cachable objects.
get_startup_elements = app.get_startup_elements
except AttributeError:
# Skip apps that do not implement get_startup_elements.
continue
out.extend(get_startup_elements())
return out
lua_script_change_data = """
-- Generate a new change_id
local tmp = redis.call('zrevrangebyscore', KEYS[1], '+inf', '-inf', 'WITHSCORES', 'LIMIT', 0, 1)
local change_id
if next(tmp) == nil then
-- The key does not exist
change_id = ARGV[1]
else
change_id = tmp[2] + 1
end
-- Add elements to sorted set
local count = 2
while ARGV[count] do
redis.call('zadd', KEYS[1], change_id, ARGV[count])
count = count + 1
end
-- Set lowest_change_id if it does not exist
redis.call('zadd', KEYS[1], 'NX', change_id, '_config:lowest_change_id')
return change_id
"""