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import boto3
from boto3.resources.base import ServiceResource
from botocore.exceptions import ClientError
from . import BaseCache, BaseStorage, get_valid_kwargs
class DynamoDbCache(BaseCache):
"""DynamoDB cache backend
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
kwargs: Additional keyword arguments for :py:meth:`~boto3.session.Session.resource`
"""
def __init__(self, table_name: str = 'http_cache', connection: ServiceResource = None, **kwargs):
super().__init__(**kwargs)
self.responses = DynamoDbDict(table_name, 'responses', connection=connection, **kwargs)
self.redirects = DynamoDbDict(table_name, 'redirects', connection=self.responses.connection, **kwargs)
class DynamoDbDict(BaseStorage):
"""A dictionary-like interface for DynamoDB key-value store
**Note:** The actual key name on the dynamodb server will be ``namespace``:``table_name``
In order to deal with how dynamodb stores data/keys,
everything, i.e. keys and data, must be pickled.
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
kwargs: Additional keyword arguments for :py:meth:`~boto3.session.Session.resource`
"""
def __init__(
self,
table_name,
namespace='http_cache',
connection=None,
read_capacity_units=1,
write_capacity_units=1,
**kwargs,
):
super().__init__(**kwargs)
connection_kwargs = get_valid_kwargs(boto3.Session, kwargs, extras=['endpoint_url'])
self.connection = connection or boto3.resource('dynamodb', **connection_kwargs)
self._self_key = namespace
try:
self.connection.create_table(
AttributeDefinitions=[
{
'AttributeName': 'namespace',
'AttributeType': 'S',
},
{
'AttributeName': 'key',
'AttributeType': 'S',
},
],
TableName=table_name,
KeySchema=[
{'AttributeName': 'namespace', 'KeyType': 'HASH'},
{'AttributeName': 'key', 'KeyType': 'RANGE'},
],
ProvisionedThroughput={
'ReadCapacityUnits': read_capacity_units,
'WriteCapacityUnits': write_capacity_units,
},
)
except ClientError:
pass
self._table = self.connection.Table(table_name)
self._table.wait_until_exists()
def __getitem__(self, key):
composite_key = {'namespace': self._self_key, 'key': str(key)}
result = self._table.get_item(Key=composite_key)
if 'Item' not in result:
raise KeyError
return self.deserialize(result['Item']['value'].value)
def __setitem__(self, key, item):
item = {'namespace': self._self_key, 'key': str(key), 'value': self.serialize(item)}
self._table.put_item(Item=item)
def __delitem__(self, key):
composite_key = {'namespace': self._self_key, 'key': str(key)}
response = self._table.delete_item(Key=composite_key, ReturnValues='ALL_OLD')
if 'Attributes' not in response:
raise KeyError
def __len__(self):
return self.__count_table()
def __iter__(self):
response = self.__scan_table()
for v in response['Items']:
yield v['key']
def clear(self):
response = self.__scan_table()
for v in response['Items']:
composite_key = {'namespace': v['namespace'], 'key': v['key']}
self._table.delete_item(Key=composite_key)
def __scan_table(self):
expression_attribute_values = {':Namespace': self._self_key}
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 __count_table(self):
expression_attribute_values = {':Namespace': self._self_key}
expression_attribute_names = {'#N': 'namespace'}
key_condition_expression = '#N = :Namespace'
return self._table.query(
Select='COUNT',
ExpressionAttributeValues=expression_attribute_values,
ExpressionAttributeNames=expression_attribute_names,
KeyConditionExpression=key_condition_expression,
)['Count']
|
