
.. _list-of-available-storages:

List of Available Storages
==========================

jIO saves his job queue in a workspace which is localStorage by default.
Provided storage descriptions are also stored, and it can be dangerous to
store passwords.

The best way to create a storage description is to use the (often) provided
tool given by the storage library. The returned description is secured to avoid
cleartext, readable passwords (as opposed to encrypted passwords for instance).

When building storage trees, there is no limit on the number of storages you
can use. The only thing you have to be aware of is compatibility of simple and
revision based storages.


Connectors
----------

LocalStorage
^^^^^^^^^^^^

Three methods are provided:

* ``.createDescription(username, [application_name], [mode='localStorage'])``
* ``.createLocalDescription(username, [application_name])``
* ``.createMemoryDescription(username, [application_name])``

All parameters are strings.

Examples:

.. code-block:: javascript

    // to work on browser localStorage
    var jio = jIO.createJIO(local_storage.createDescription('me'));

    // to work on browser memory
    var jio = jIO.createJIO(local_storage.createMemoryDescription('me'));

    // or
    {
      "type": "local",
      "username": "me",
      "application_name": "my app name", // optional
      "mode": "memory" // optional, "localStorage" by default
    }

DavStorage
^^^^^^^^^^

The method ``dav_storage.createDescription()`` generates a DAV storage description for
*none*, *basic* or *digest* authentication.

NB: digest **is not implemented yet**.

.. code-block:: javascript

  dav_storage.createDescription(url, auth_type,
                                [realm], [username], [password]);

All parameters are strings.

=============   ========================
parameter       required?
=============   ========================
``url``         yes
``auth_type``   yes
``realm``       if auth_type == 'digest'
``username``    if auth_type != 'none'
``password``    if auth-type != 'none'
=============   ========================

If ``auth_type`` is the string ``"none"``, then ``realm``, ``username`` and ``password`` are never used.

Descriptions:

.. code-block:: javascript

  // No authentication
  {
    "type": "dav",
    "url": url
  }

  // Basic authentication
  {
    "type": "dav",
    "url": "url,
    "basic_login": btoa(username + ":" + password)
  }

  // Digest authentication is not implemented

**Be careful**: The generated description never contains a readable password, but
for basic authentication, the password is just base64 encoded.

S3Storage
^^^^^^^^^

Live tests OK!

Here is a basic description for jIO. Documentation comming soon.

.. code-block:: javascript

  {
    "type": "s3",
    "AWSIdentifier": "my aws identifier",
    "password": "my password",
    "server": "bucket_name"
  }

XWikiStorage
^^^^^^^^^^^^

Work is in progress.

Searchable Encryption Storage
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Comes with a specific server with can query encrypted documents.

Work is in progress. Documentation comming soon.

.. code-block:: javascript

  {
    "type": "searchableencryption",
    "password": "your password",
    "url": "http://your/url"
  }

Handlers
--------

IndexStorage
^^^^^^^^^^^^

This handler indexes documents metadata into a database (which is a simple
document) to increase the speed of ``.allDocs()`` requests. However, it is not able to
manage the ``include_docs`` option.

Here is the description:

.. code-block:: javascript

   {
     type: 'index',
     indices: [{
       // doc id where to store indices
       id: 'index_title_subject.json',
       // metadata to index
       index: ['title', 'subject'],
       attachment: 'db.json', // default 'body'
       // additional metadata to add to database, default undefined
       metadata: {
         type: 'Dataset',
         format: 'application/json',
         title: 'My index database',
         creator: 'Me'
       },
       // default equal to parent sub_storage field
       sub_storage: <sub storage where to store index>
     }, {
       id: 'index_year.json',
       index: 'year'
       ...
     }],
     sub_storage: <sub storage description>
   }


GIDStorage
^^^^^^^^^^

:ref:`Full description here <gid-storage>`.

SplitStorage
^^^^^^^^^^^^

Work is in progress. The interoperability is not enabled yet.

This storage splits metadata and attachment data to *n* parts where *n* is the
number of sub storages. Each parts are stored on one sub storage only.

.. code-block:: javascript

   {
     type: 'split',
     storage_list: [
       <sub storage description>,
       ...
     ]
   }

Other split modes will be added later.


Replicate Storage
^^^^^^^^^^^^^^^^^

Work is in progress.

.. code-block:: javascript

   {
     type: 'replicate',
     storage_list: [
       <sub storage description>,
       ...
     ]
   }


Revision Based Handlers
-----------------------

A revision based handler is a storage which is able to do some document
versioning using simple storages listed above.

On jIO command parameter, ``_id`` is still used to identify a document, but
another id ``_rev`` must be defined to use a specific revision of that document.

On command responses, you will find another field ``rev`` which will represent the
new revision produced by your action. All the document history is kept unless
you decide to delete older revisions.

Other fields ``conflicts``, ``revisions`` and ``revs_info`` can be returned if the
options **conflicts: true**, **revs: true** or **revs_info: true** are set.

Revision Storage
^^^^^^^^^^^^^^^^

This backend uses its sub storage to manage document and their revision. For
more information, :ref:`see here <revision-storages-conflicts-and-resolution>`.

Description:

.. code-block:: javascript

  {
    "type": "revision",
    "sub_storage": <sub storage description>
  }


Replicate Revision Storage
^^^^^^^^^^^^^^^^^^^^^^^^^^

Replicate revisions across multiple revision based storages.

Description:

.. code-block:: javascript

  {
    "type": "revision",
    "storage_list": [
      <revision based sub storage description>,
      ...
    ]
  }
