DynamoDB

../_images/dynamodb.png

DynamoDB is a NoSQL document database hosted on Amazon Web Services. In terms of features and use cases, it is roughly comparable to MongoDB and other NoSQL databases. It is an especially good fit for serverless applications running on AWS Lambda.

Warning

DynamoDB binary item sizes are limited to 400KB. If you need to cache larger responses, consider using a different backend.

Creating Tables

Tables will be automatically created if they don’t already exist. This is convienient if you just want to quickly test out DynamoDB as a cache backend, but in a production environment you will likely want to create the tables yourself, for example with CloudFormation or Terraform. Here are the details you’ll need:

  • Tables: two tables, named responses and redirects

  • Partition key (aka namespace): namespace

  • Range key (aka sort key): key

  • Attributes: namespace (string) and key (string)

Connection Options

The DynamoDB backend accepts any keyword arguments for boto3.session.Session.resource(). These can be passed via CachedSession:

>>> session = CachedSession('http_cache', backend='dynamodb', region_name='us-west-2')

Or via DynamoDbCache:

>>> backend = DynamoDbCache(region_name='us-west-2')
>>> session = CachedSession('http_cache', backend=backend)

API Reference

DynamoDbCache

DynamoDB cache backend

DynamoDbDict

A dictionary-like interface for DynamoDB key-value store

class requests_cache.backends.dynamodb.DynamoDbCache(table_name='http_cache', connection=None, **kwargs)[source]

Bases: requests_cache.backends.base.BaseCache

DynamoDB cache backend

Parameters
bulk_delete(keys)

Remove multiple responses and their associated redirects from the cache

Parameters

keys (Iterable[str]) –

clear()

Delete all items from the cache

create_key(request=None, **kwargs)

Create a normalized cache key from a request object

Parameters

request (Union[Request, PreparedRequest, CachedRequest, None]) –

Return type

str

delete(key)

Delete a response or redirect from the cache, as well any associated redirect history

Parameters

key (str) –

delete_url(url, method='GET', **kwargs)

Delete a cached response for the specified request

Parameters
  • url (str) –

  • method (str) –

delete_urls(urls, method='GET', **kwargs)

Delete all cached responses for the specified requests

Parameters
get_response(key, default=None)

Retrieve a response from the cache, if it exists

Parameters
  • key (str) – Cache key for the response

  • default – Value to return if key is not in the cache

Return type

Optional[CachedResponse]

has_key(key)

Returns True if key is in the cache

Parameters

key (str) –

Return type

bool

has_url(url, method='GET', **kwargs)

Returns True if the specified request is cached

Parameters
  • url (str) –

  • method (str) –

Return type

bool

keys(check_expiry=False)

Get all cache keys for redirects and valid responses combined

Return type

Iterator[str]

remove_expired_responses(expire_after=None)

Remove expired and invalid responses from the cache, optionally with revalidation

Parameters

expire_after (Union[None, int, float, str, datetime, timedelta]) – A new expiration time used to revalidate the cache

response_count(check_expiry=False)

Get the number of responses in the cache, excluding invalid (unusable) responses. Can also optionally exclude expired responses.

Return type

int

save_response(response, cache_key=None, expires=None)

Save a response to the cache

Parameters
update(other)

Update this cache with the contents of another cache

Parameters

other (BaseCache) –

property urls

Get all URLs currently in the cache (excluding redirects)

Return type

Iterator[str]

values(check_expiry=False)

Get all valid response objects from the cache

Return type

Iterator[CachedResponse]

class requests_cache.backends.dynamodb.DynamoDbDict(table_name, namespace='http_cache', connection=None, read_capacity_units=1, write_capacity_units=1, **kwargs)[source]

Bases: requests_cache.backends.base.BaseStorage

A dictionary-like interface for DynamoDB key-value store

Notes:
  • The actual table name on the Dynamodb server will be namespace:table_name

  • In order to deal with how DynamoDB stores data, all values are serialized.

Parameters
  • table_name – DynamoDB table name

  • namespace – Name of DynamoDB hash map

  • connectionDynamoDB Resource object to use instead of creating a new one

  • kwargs – Additional keyword arguments for resource()

bulk_delete(keys)[source]

Delete multiple keys from the cache. Does not raise errors for missing keys.

Parameters

keys (Iterable[str]) –

clear() None.  Remove all items from D.[source]
composite_key(key)[source]
Parameters

key (str) –

Return type

Dict[str, str]

get(k[, d]) D[k] if k in D, else d.  d defaults to None.
items() a set-like object providing a view on D's items
keys() a set-like object providing a view on D's keys
pop(k[, d]) v, remove specified key and return the corresponding value.

If key is not found, d is returned if given, otherwise KeyError is raised.

popitem() (k, v), remove and return some (key, value) pair

as a 2-tuple; but raise KeyError if D is empty.

property serializer
setdefault(k[, d]) D.get(k,d), also set D[k]=d if k not in D
update([E, ]**F) None.  Update D from mapping/iterable E and F.

If E present and has a .keys() method, does: for k in E: D[k] = E[k] If E present and lacks .keys() method, does: for (k, v) in E: D[k] = v In either case, this is followed by: for k, v in F.items(): D[k] = v

values() an object providing a view on D's values