OpenSlides/openslides/utils/cache_providers.py

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from collections import defaultdict
from typing import (
TYPE_CHECKING,
Any,
Dict,
Generator,
Iterable,
List,
Optional,
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Set,
Tuple,
Union,
)
from django.apps import apps
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 BaseCacheProvider:
"""
Base class for cache provider.
See RedisCacheProvider as reverence implementation.
"""
full_data_cache_key = 'full_data_cache'
restricted_user_cache_key = 'restricted_data_cache:{user_id}'
change_id_cache_key = 'change_id_cache'
lock_key = '_config:updating'
def __init__(self, *args: Any) -> None:
pass
def get_full_data_cache_key(self) -> str:
return self.full_data_cache_key
def get_restricted_data_cache_key(self, user_id: int) -> str:
return self.restricted_user_cache_key.format(user_id=user_id)
def get_change_id_cache_key(self) -> str:
return self.change_id_cache_key
def clear_cache(self) -> None:
raise NotImplementedError("CacheProvider has to implement the method clear_cache().")
async def reset_full_cache(self, data: Dict[str, str]) -> None:
raise NotImplementedError("CacheProvider has to implement the method reset_full_cache().")
async def data_exists(self, user_id: Optional[int] = None) -> bool:
raise NotImplementedError("CacheProvider has to implement the method exists_full_data().")
async def add_elements(self, elements: List[str]) -> None:
raise NotImplementedError("CacheProvider has to implement the method add_elements().")
async def del_elements(self, elements: List[str], user_id: Optional[int] = None) -> None:
raise NotImplementedError("CacheProvider has to implement the method del_elements().")
async def add_changed_elements(self, change_id: int, element_ids: Iterable[str]) -> None:
raise NotImplementedError("CacheProvider has to implement the method add_changed_elements().")
async def get_all_data(self, user_id: Optional[int] = None) -> Dict[bytes, bytes]:
raise NotImplementedError("CacheProvider has to implement the method get_all_data().")
async def get_data_since(self, change_id: int, user_id: Optional[int] = None) -> Tuple[Dict[str, List[bytes]], List[str]]:
raise NotImplementedError("CacheProvider has to implement the method get_data_since().")
async def get_element(self, element_id: str) -> Optional[bytes]:
raise NotImplementedError("CacheProvider has to implement the method get_element().")
async def del_restricted_data(self, user_id: int) -> None:
raise NotImplementedError("CacheProvider has to implement the method del_restricted_data().")
async def set_lock_restricted_data(self, user_id: int) -> bool:
raise NotImplementedError("CacheProvider has to implement the method set_lock_restricted_data().")
async def get_lock_restricted_data(self, user_id: int) -> bool:
raise NotImplementedError("CacheProvider has to implement the method get_lock_restricted_data().")
async def del_lock_restricted_data(self, user_id: int) -> None:
raise NotImplementedError("CacheProvider has to implement the method del_lock_restricted_data().")
async def get_change_id_user(self, user_id: int) -> Optional[int]:
raise NotImplementedError("CacheProvider has to implement the method get_change_id_user().")
async def update_restricted_data(self, user_id: int, data: Dict[str, str]) -> None:
raise NotImplementedError("CacheProvider has to implement the method update_restricted_data().")
async def get_current_change_id(self) -> List[Tuple[str, int]]:
raise NotImplementedError("CacheProvider has to implement the method get_current_change_id().")
async def get_lowest_change_id(self) -> Optional[int]:
raise NotImplementedError("CacheProvider has to implement the method get_lowest_change_id().")
class RedisCacheProvider(BaseCacheProvider):
"""
Cache provider that loads and saves the data to redis.
"""
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redis_pool: Optional[aioredis.RedisConnection] = None
def __init__(self, redis: str) -> None:
self.redis_address = redis
async def get_connection(self) -> 'aioredis.RedisConnection':
"""
Returns a redis connection.
"""
if self.redis_pool is None:
self.redis_pool = await aioredis.create_redis_pool(self.redis_address)
return self.redis_pool
async def reset_full_cache(self, data: Dict[str, str]) -> None:
"""
Deletes the cache and write new data in it.
"""
# TODO: lua or transaction
redis = await self.get_connection()
await redis.delete(self.get_full_data_cache_key())
await redis.hmset_dict(self.get_full_data_cache_key(), data)
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.
"""
redis = await self.get_connection()
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.
"""
redis = await self.get_connection()
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.
"""
redis = await self.get_connection()
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, change_id: int, element_ids: Iterable[str]) -> None:
"""
Saves which elements are change with a change_id.
args has to be an even iterable. The odd values have to be a change id (int) and the
even values have to be element_ids.
"""
def zadd_args(change_id: int) -> Generator[Union[int, str], None, None]:
"""
Small helper to generates the arguments for the redis command zadd.
"""
for element_id in element_ids:
yield change_id
yield element_id
redis = await self.get_connection()
await redis.zadd(self.get_change_id_cache_key(), *zadd_args(change_id))
# Saves the lowest_change_id if it does not exist
await redis.zadd(self.get_change_id_cache_key(), change_id, '_config:lowest_change_id', exist='ZSET_IF_NOT_EXIST')
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)
redis = await self.get_connection()
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.
"""
redis = await self.get_connection()
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) -> 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.
"""
# TODO: rewrite with lua to get all elements with one request
redis = await self.get_connection()
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changed_elements: Dict[str, List[bytes]] = defaultdict(list)
deleted_elements: List[str] = []
for element_id in await redis.zrangebyscore(self.get_change_id_cache_key(), min=change_id):
if element_id.startswith(b'_config'):
continue
element_json = await redis.hget(self.get_full_data_cache_key(), element_id) # Optional[bytes]
if element_json is None:
# The element is not in the cache. It has to be deleted.
deleted_elements.append(element_id)
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.
"""
redis = await self.get_connection()
await redis.delete(self.get_restricted_data_cache_key(user_id))
async def set_lock_restricted_data(self, user_id: int) -> bool:
"""
Tries to sets a lock for the restricted_data of an user.
Returns True when the lock could be set.
Returns False when the lock was already set.
"""
redis = await self.get_connection()
return await redis.hsetnx(self.get_restricted_data_cache_key(user_id), self.lock_key, 1)
async def get_lock_restricted_data(self, user_id: int) -> bool:
"""
Returns True, when the lock for the restricted_data of an user is set. Else False.
"""
redis = await self.get_connection()
return await redis.hget(self.get_restricted_data_cache_key(user_id), self.lock_key)
async def del_lock_restricted_data(self, user_id: int) -> None:
"""
Deletes the lock for the restricted_data of an user. Does nothing when the
lock is not set.
"""
redis = await self.get_connection()
await redis.hdel(self.get_restricted_data_cache_key(user_id), self.lock_key)
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.
"""
redis = await self.get_connection()
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.
"""
redis = await self.get_connection()
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.
"""
redis = await self.get_connection()
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.
"""
redis = await self.get_connection()
return await redis.zscore(
self.get_change_id_cache_key(),
'_config:lowest_change_id')
class MemmoryCacheProvider(BaseCacheProvider):
"""
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:
self.clear_cache()
def clear_cache(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]] = {}
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, change_id: int, element_ids: Iterable[str]) -> None:
element_ids = list(element_ids)
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}
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) -> 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:
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
async def set_lock_restricted_data(self, user_id: int) -> bool:
data = self.restricted_data.setdefault(user_id, {})
if self.lock_key in data:
return False
data[self.lock_key] = "1"
return True
async def get_lock_restricted_data(self, user_id: int) -> bool:
data = self.restricted_data.get(user_id, {})
return self.lock_key in data
async def del_lock_restricted_data(self, user_id: int) -> None:
data = self.restricted_data.get(user_id, {})
try:
del data[self.lock_key]
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:
"""
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.
"""
raise NotImplementedError("Cachable has to implement the method get_collection_string().")
def get_elements(self) -> List[Dict[str, Any]]:
"""
Returns all elements of the cachable.
"""
raise NotImplementedError("Cachable has to implement the method get_collection_string().")
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.
The default implementation returns the full_data.
"""
return elements
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 Collection 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