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"""DynamoDB cache backend. For usage details, see :ref:`Backends: DynamoDB <dynamodb>`.
.. automodsumm:: requests_cache.backends.dynamodb
:classes-only:
:nosignatures:
"""
from typing import Iterable, Optional
import boto3
from boto3.dynamodb.types import Binary
from boto3.resources.base import ServiceResource
from botocore.exceptions import ClientError
from requests_cache.backends.base import VT
from .._utils import get_valid_kwargs
from ..serializers import SerializerType, dynamodb_document_serializer
from . import BaseCache, BaseStorage, DictStorage
class DynamoDbCache(BaseCache):
"""DynamoDB cache backend.
By default, responses are only partially serialized into a DynamoDB-compatible document format.
Args:
table_name: DynamoDB table name
connection: :boto3:`DynamoDB Resource <services/dynamodb/service-resource/index.html#service-resource>`
object to use instead of creating a new one
ttl: Use DynamoDB TTL to automatically remove expired items
kwargs: Additional keyword arguments for :py:meth:`~boto3.session.Session.resource`
"""
def __init__(
self,
table_name: str = 'http_cache',
*,
ttl: bool = True,
connection: Optional[ServiceResource] = None,
decode_content: bool = True,
serializer: Optional[SerializerType] = None,
**kwargs,
):
super().__init__(cache_name=table_name, **kwargs)
skwargs = {'serializer': serializer, **kwargs} if serializer else kwargs
self.responses = DynamoDbDict(
table_name,
ttl=ttl,
connection=connection,
decode_content=decode_content,
**skwargs,
)
# Redirects will be only stored in memory and not persisted
self.redirects: BaseStorage[str, str] = DictStorage()
class DynamoDbDict(BaseStorage):
"""A dictionary-like interface for DynamoDB table
Args:
table_name: DynamoDB table name
connection: :boto3:`DynamoDB Resource <services/dynamodb/service-resource/index.html#service-resource>`
object to use instead of creating a new one
ttl: Use DynamoDB TTL to automatically remove expired items
kwargs: Additional keyword arguments for :py:meth:`~boto3.session.Session.resource`
"""
def __init__(
self,
table_name: str,
ttl: bool = True,
connection: Optional[ServiceResource] = None,
serializer: Optional[SerializerType] = dynamodb_document_serializer,
**kwargs,
):
super().__init__(serializer=serializer, **kwargs)
connection_kwargs = get_valid_kwargs(
boto3.Session.__init__, kwargs, extras=['endpoint_url']
)
self.connection = connection or boto3.resource('dynamodb', **connection_kwargs)
self.table_name = table_name
self.ttl = ttl
self._table = self.connection.Table(self.table_name)
self._create_table()
if ttl:
self._enable_ttl()
def _create_table(self):
"""Create a default table if one does not already exist"""
try:
self.connection.create_table(
AttributeDefinitions=[
{'AttributeName': 'key', 'AttributeType': 'S'},
],
TableName=self.table_name,
KeySchema=[
{'AttributeName': 'key', 'KeyType': 'HASH'},
],
BillingMode='PAY_PER_REQUEST',
)
self._table.wait_until_exists()
# Ignore error if table already exists
except ClientError as e:
if e.response['Error']['Code'] != 'ResourceInUseException':
raise
def _enable_ttl(self):
"""Enable TTL, if not already enabled"""
try:
self.connection.meta.client.update_time_to_live(
TableName=self.table_name,
TimeToLiveSpecification={'AttributeName': 'ttl', 'Enabled': True},
)
# Ignore error if TTL is already enabled
except ClientError as e:
if e.response['Error']['Code'] != 'ValidationException':
raise
def __getitem__(self, key):
result = self._table.get_item(Key={'key': key})
if 'Item' not in result:
raise KeyError
return self.deserialize(key, result['Item']['value'])
def __setitem__(self, key, value):
item = {'key': key, 'value': self.serialize(value)}
# If enabled, set TTL value as a timestamp in unix format
if self.ttl and getattr(value, 'expires_unix', None):
item['ttl'] = value.expires_unix
self._table.put_item(Item=item)
def __delitem__(self, key):
response = self._table.delete_item(Key={'key': key}, ReturnValues='ALL_OLD')
if 'Attributes' not in response:
raise KeyError
def __iter__(self):
# Alias 'key' attribute since it's a reserved keyword
results = self._table.scan(
ProjectionExpression='#k',
ExpressionAttributeNames={'#k': 'key'},
)
for item in results['Items']:
yield item['key']
def __len__(self):
"""Get the number of items in the table.
**Note:** This is an estimate, and is updated every 6 hours. A full table scan will use up
your provisioned throughput, so it's not recommended.
"""
return self._table.item_count
def bulk_delete(self, keys: Iterable[str]):
"""Delete multiple keys from the cache. Does not raise errors for missing keys."""
with self._table.batch_writer() as batch:
for key in keys:
batch.delete_item(Key={'key': key})
def clear(self):
self.bulk_delete((k for k in self))
def deserialize(self, key, value: VT):
"""Handle Binary objects from a custom serializer"""
serialized_value = value.value if isinstance(value, Binary) else value
return super().deserialize(key, serialized_value)
# TODO: Support pagination
def values(self):
for item in self._table.scan()['Items']:
yield self.deserialize(item['key'], item['value'])
|
