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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 Dict, Iterable, Optional
import boto3
from boto3.dynamodb.types import Binary
from boto3.resources.base import ServiceResource
from botocore.exceptions import ClientError
from .._utils import get_valid_kwargs
from ..serializers import dynamodb_document_serializer
from . import BaseCache, BaseStorage
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
namespace: Name of DynamoDB hash map
connection: :boto3:`DynamoDB Resource <services/dynamodb.html#DynamoDB.ServiceResource>`
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,
**kwargs,
):
super().__init__(cache_name=table_name, **kwargs)
self.responses = DynamoDbDict(
table_name,
namespace='responses',
ttl=ttl,
connection=connection,
decode_content=decode_content,
**kwargs,
)
self.redirects = DynamoDbDict(
table_name,
namespace='redirects',
ttl=False,
connection=self.responses.connection,
no_serializer=True,
**kwargs,
)
class DynamoDbDict(BaseStorage):
"""A dictionary-like interface for DynamoDB table
Args:
table_name: DynamoDB table name
namespace: Name of DynamoDB hash map
connection: :boto3:`DynamoDB Resource <services/dynamodb.html#DynamoDB.ServiceResource>`
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`
"""
default_serializer = dynamodb_document_serializer
def __init__(
self,
table_name: str,
namespace: str,
ttl: bool = True,
connection: Optional[ServiceResource] = None,
**kwargs,
):
super().__init__(**kwargs)
connection_kwargs = get_valid_kwargs(
boto3.Session.__init__, kwargs, extras=['endpoint_url']
)
self.connection = connection or boto3.resource('dynamodb', **connection_kwargs)
self.namespace = namespace
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': 'namespace', 'AttributeType': 'S'},
{'AttributeName': 'key', 'AttributeType': 'S'},
],
TableName=self.table_name,
KeySchema=[
{'AttributeName': 'namespace', 'KeyType': 'HASH'},
{'AttributeName': 'key', 'KeyType': 'RANGE'},
],
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 _composite_key(self, key: str) -> Dict[str, str]:
return {'namespace': self.namespace, 'key': str(key)}
def _scan(self):
expression_attribute_values = {':Namespace': self.namespace}
expression_attribute_names = {'#N': 'namespace'}
key_condition_expression = '#N = :Namespace'
return self._table.query(
ExpressionAttributeValues=expression_attribute_values,
ExpressionAttributeNames=expression_attribute_names,
KeyConditionExpression=key_condition_expression,
)
def __getitem__(self, key):
result = self._table.get_item(Key=self._composite_key(key))
if 'Item' not in result:
raise KeyError
# With a custom serializer, the value may be a Binary object
raw_value = result['Item']['value']
value = raw_value.value if isinstance(raw_value, Binary) else raw_value
return self.deserialize(key, value)
def __setitem__(self, key, value):
item = {**self._composite_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=self._composite_key(key), ReturnValues='ALL_OLD')
if 'Attributes' not in response:
raise KeyError
def __iter__(self):
response = self._scan()
for item in response['Items']:
yield item['key']
def __len__(self):
return self._table.query(
Select='COUNT',
ExpressionAttributeNames={'#N': 'namespace'},
ExpressionAttributeValues={':Namespace': self.namespace},
KeyConditionExpression='#N = :Namespace',
)['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=self._composite_key(key))
def clear(self):
self.bulk_delete((k for k in self))
|
