Storage¶
Backends¶
PostgreSQL¶
-
class
cliquet.storage.postgresql.
PostgreSQL
(*args, **kwargs)¶ Storage backend using PostgreSQL.
Recommended in production (requires PostgreSQL 9.4 or higher).
Enable in configuration:
cliquet.storage_backend = cliquet.storage.postgresql
Database location URI can be customized:
cliquet.storage_url = postgres://user:pass@db.server.lan:5432/dbname
Alternatively, username and password could also rely on system user ident or even specified in
~/.pgpass
(see PostgreSQL documentation).Note
Some tables and indices are created when
cliquet migrate
is run. This requires some privileges on the database, or some error will be raised.Alternatively, the schema can be initialized outside the python application, using the SQL file located in
cliquet/storage/postgresql/schema.sql
. This allows to distinguish schema manipulation privileges from schema usage.A threaded connection pool is enabled by default:
cliquet.storage_pool_size = 10
Note
Using a dedicated connection pool is still recommended to allow load balancing, replication or limit the number of connections used in a multi-process deployment.
Redis¶
-
class
cliquet.storage.redis.
Redis
(*args, **kwargs)¶ Storage backend implementation using Redis.
Warning
Useful for very low server load, but won’t scale since records sorting and filtering are performed in memory.
Enable in configuration:
cliquet.storage_backend = cliquet.storage.redis
(Optional) Instance location URI can be customized:
cliquet.storage_url = redis://localhost:6379/0
A threaded connection pool is enabled by default:
cliquet.storage_pool_size = 50
Memory¶
-
class
cliquet.storage.memory.
Memory
(*args, **kwargs)¶ Storage backend implementation in memory.
Useful for development or testing purposes, but records are lost after each server restart.
Enable in configuration:
cliquet.storage_backend = cliquet.storage.memory
Cloud Storage¶
If the kinto
package is available, it is possible to store data in
a remote instance of Kinto.
cliquet.storage_backend = kinto.storage
cliquet.storage_url = https://cloud-storage.services.mozilla.com
See Kinto for more details.
Note
In order to avoid double checking of OAuth tokens, the Kinto service
and the application can share the same cache (cliquet.cache_url
).
API¶
Implementing a custom storage backend consists in implementating the following interface:
-
class
cliquet.storage.
Filter
(field, value, operator)¶ Filtering properties.
-
field
¶ Alias for field number 0
-
operator
¶ Alias for field number 2
-
value
¶ Alias for field number 1
-
-
class
cliquet.storage.
Sort
(field, direction)¶ Sorting properties.
-
direction
¶ Alias for field number 1
-
field
¶ Alias for field number 0
-
-
class
cliquet.storage.
StorageBase
¶ Storage abstraction used by resource views.
It is meant to be instantiated at application startup. Any operation may raise a HTTPServiceUnavailable error if an error occurs with the underlying service.
Configuration can be changed to choose which storage backend will persist the objects.
Raises: HTTPServiceUnavailable
-
initialize_schema
()¶ Create every necessary objects (like tables or indices) in the backend.
This is excuted when the
cliquet migrate
command is ran.
-
flush
(auth=None)¶ Remove every object from this storage.
-
ping
(request)¶ Test that storage is operationnal.
Parameters: request ( Request
) – current request objectReturns: True
is everything is ok,False
otherwise.Return type: bool
-
collection_timestamp
(collection_id, parent_id, auth=None)¶ Get the highest timestamp of every objects in this collection_id for this parent_id.
Note
This should take deleted objects into account.
Parameters: - collection_id (str) – the collection id.
- parent_id (str) – the collection parent.
Returns: the latest timestamp of the collection.
Return type: int
-
create
(collection_id, parent_id, object, id_generator=None, unique_fields=None, id_field='id', modified_field='last_modified', auth=None)¶ Create the specified object in this collection_id for this parent_id. Assign the id to the object, using the attribute
cliquet.resource.BaseResource.id_field
.Note
This will update the collection timestamp.
Raises: Parameters: - collection_id (str) – the collection id.
- parent_id (str) – the collection parent.
- object (dict) – the object to create.
Returns: the newly created object.
Return type: dict
-
get
(collection_id, parent_id, object_id, id_field='id', modified_field='last_modified', auth=None)¶ Retrieve the object with specified object_id, or raise error if not found.
Raises: Parameters: - collection_id (str) – the collection id.
- parent_id (str) – the collection parent.
- object_id (str) – unique identifier of the object
Returns: the object object.
Return type: dict
-
update
(collection_id, parent_id, object_id, object, unique_fields=None, id_field='id', modified_field='last_modified', auth=None)¶ Overwrite the object with the specified object_id.
If the specified id is not found, the object is created with the specified id.
Note
This will update the collection timestamp.
Raises: Parameters: - collection_id (str) – the collection id.
- parent_id (str) – the collection parent.
- object_id (str) – unique identifier of the object
- object (dict) – the object to update or create.
Returns: the updated object.
Return type: dict
-
delete
(collection_id, parent_id, object_id, id_field='id', modified_field='last_modified', deleted_field='deleted', auth=None)¶ Delete the object with specified object_id, and raise error if not found.
Deleted objects must be removed from the database, but their ids and timestamps of deletion must be tracked for synchronization purposes. (See
cliquet.storage.StorageBase.get_all()
)Note
This will update the collection timestamp.
Raises: Parameters: - collection_id (str) – the collection id.
- parent_id (str) – the collection parent.
- object_id (str) – unique identifier of the object
Returns: the deleted object, with minimal set of attributes.
Return type: dict
-
delete_all
(collection_id, parent_id, filters=None, id_field='id', modified_field='last_modified', deleted_field='deleted', auth=None)¶ Delete all objects in this collection_id for this parent_id.
Parameters: - collection_id (str) – the collection id.
- parent_id (str) – the collection parent.
- filters (list of
cliquet.storage.Filter
) – Optionnally filter the objects to delete.
Returns: the list of deleted objects, with minimal set of attributes.
Return type: list of dict
-
get_all
(collection_id, parent_id, filters=None, sorting=None, pagination_rules=None, limit=None, include_deleted=False, id_field='id', modified_field='last_modified', deleted_field='deleted', auth=None)¶ Retrieve all objects in this collection_id for this parent_id.
Parameters: - collection_id (str) – the collection id.
- parent_id (str) – the collection parent.
- filters (list of
cliquet.storage.Filter
) – Optionally filter the objects by their attribute. Each filter in this list is a tuple of a field, a value and a comparison (see cliquet.utils.COMPARISON). All filters are combined using AND. - sorting (list of
cliquet.storage.Sort
) – Optionnally sort the objects by attribute. Each sort instruction in this list refers to a field and a direction (negative means descending). All sort instructions are cumulative. - pagination_rules (list of list of
cliquet.storage.Filter
) – Optionnally paginate the list of objects. This list of rules aims to reduce the set of objects to the current page. A rule is a list of filters (see filters parameter), and all rules are combined using OR. - limit (int) – Optionnally limit the number of objects to be retrieved.
- include_deleted (bool) – Optionnally include the deleted objects that match the filters.
Returns: the limited list of objects, and the total number of matching objects in the collection (deleted ones excluded).
Return type: tuple (list, integer)
-
Exceptions¶
Exceptions raised by storage backend.
-
exception
cliquet.storage.exceptions.
BackendError
(original=None, message=None, *args, **kwargs)¶ A generic exception raised by storage on error.
Parameters: original (Exception) – the wrapped exception raised by underlying library.
-
exception
cliquet.storage.exceptions.
RecordNotFoundError
¶ An exception raised when a specific record could not be found.
-
exception
cliquet.storage.exceptions.
UnicityError
(field, record, *args, **kwargs)¶ An exception raised on unicity constraint violation.
Raised by storage backend when the creation or the modification of a record violates the unicity constraints defined by the resource.
Store custom data¶
Storage can be used to store arbitrary data.
data = {'subscribed': datetime.now()}
user_id = request.authenticated_userid
storage = request.registry.storage
storage.create(collection_id='__custom', parent_id='', record=data)
See the collection class to manipulate collections of records.