MongoDb Backend

class cachelib.mongodb.MongoDbCache(client=None, db='cache-db', collection='cache-collection', default_timeout=300, key_prefix=None, ignore_delete_many_errors=True, check_connection=False, **kwargs)

Bases: BaseCache

Implementation of BaseCache that uses mongodb collection as the backend.

Limitations: maximum MongoDB document size is 16 MB

Parameters:

  • client (Any) – mongodb client or connection string

  • db (str) – mongodb database name

  • collection (str) – mongodb collection name

  • default_timeout (int | timedelta) –

    Set the timeout after which cache entries expire, either a number of seconds or a datetime.timedelta

    Changed in version 0.17.0: Accepts a datetime.timedelta.

  • key_prefix (str | None) – A prefix that should be added to all keys.

  • ignore_delete_many_errors (bool) –

    If False, delete_many() will raise a RuntimeError if any key fails to delete. Keys that do not exist are considered successfully deleted and do not raise.

    Changelog

    Added in version 0.16.0.

  • check_connection (bool) –

    If True, the constructor will verify the connection to the mongodb server and raise a RuntimeError if it fails. If False (default), connection errors are ignored at construction and surface on first use.

    Changelog

    Added in version 0.16.1.

  • kwargs (Any)

serializer = <cachelib.serializers.MongoDbSerializer object>
get(key)

Get a cache item

Parameters:

key (str) – The cache key of the item to fetch

Returns:

cache value if not expired, else None

Return type:

Any

delete(key)

Deletes an item from the cache. This is a no-op if the item doesn’t exist

Parameters:

key (str) – Key of the item to delete.

Returns:

True if the key existed and was deleted

Return type:

bool

set(key, value, timeout=None)

Add a new key/value to the cache (overwrites value, if key already exists in the cache).

Parameters:

  • key (str) – the key to set

  • value (Any) – the value for the key

  • timeout (int | timedelta | None) – the cache timeout for the key, either a number of seconds or a datetime.timedelta (if not specified, it uses the default timeout). A timeout of 0 indicates that the cache never expires.

Returns:

True if key has been updated, False for backend errors. Pickling errors, however, will raise a subclass of pickle.PickleError.

Return type:

Any

set_many(mapping, timeout=None)

Sets multiple keys and values from a mapping.

Parameters:

  • mapping (dict[str, Any]) – a mapping with the keys/values to set.

  • timeout (int | timedelta | None) – the cache timeout for the key, either a number of seconds or a datetime.timedelta (if not specified, it uses the default timeout). A timeout of 0 indicates that the cache never expires.

Returns:

A list containing all keys successfully set

Return type:

list[Any]

get_many(*keys)

Returns a list of values for the given keys. For each key an item in the list is created:

foo, bar = cache.get_many("foo", "bar")

Has the same error handling as get().

Parameters:

keys (str) – The function accepts multiple keys as positional arguments.

Return type:

list[Any]

get_dict(*keys)

Like get_many() but return a dict:

d = cache.get_dict("foo", "bar")
foo = d["foo"]
bar = d["bar"]
Parameters:

keys (str) – The function accepts multiple keys as positional arguments.

Return type:

dict[str, Any]

add(key, value, timeout=None)

Works like set() but does not overwrite the values of already existing keys.

Parameters:

  • key (str) – the key to set

  • value (Any) – the value for the key

  • timeout (int | timedelta | None) – the cache timeout for the key, either a number of seconds or a datetime.timedelta (if not specified, it uses the default timeout). A timeout of 0 indicates that the cache never expires.

Returns:

Same as set(), but also False for already existing keys.

Return type:

Any

has(key)

Checks if a key exists in the cache without returning it. This is a cheap operation that bypasses loading the actual data on the backend.

Parameters:

key (str) – the key to check

Return type:

bool

delete_many(*keys)

Deletes multiple keys at once.

Parameters:

keys (str) – The function accepts multiple keys as positional arguments.

Returns:

A list containing all successfully deleted keys

Raises:

RuntimeError – If ignore_delete_many_errors is False and a key still exists after the delete attempt.

Return type:

list[Any]

clear()

Clears the cache. Keep in mind that not all caches support completely clearing the cache.

Returns:

Whether the cache has been cleared.

Return type:

bool