Button Button
valkyrie (000001)

Valkyrie Storage API

Based on Versium, originally by Yuri

  • https://github.com/swift2plunder/versium
  • http://sputnik.freewisdom.org/en/Versium

Valkyrie is a simple storage API used by YAAPS and Freya based on Versium from the Sputnik wiki. The main diffence between Versium and Valkyrie is that Versium returned completed nodes because it was created for wiki storage, where a node represented a document. Valkyrie nodes represent objects, such as ActivityPub Activities, that transform a stream. Valkyrie nodes are deltas

Each Valkyrie implementation is a Lua module that can be loaded with “require”

YAAPS is a lightweight ActivityPub implementation for experimentation and hosting federated services

Freya is a data adapter to maintain data consistency in object streams when component objects may require access via diverse schema

Capabilities

Since many parts of the API are optional, each implementation must define a table that specifies what it does and does not support

For instance:

capabilities = {
can_save = true, -- an implementation can be read-only
allow_changes = true, -- an implementation may not be able to change the contents of an existing node
has_history = true, -- some implementations don't keep track of
history is_persistent = true, -- we'll still have the data if the server goes down
supports_extra_fields = true, -- revisions can have fields other than those specified at plug in initialization
}

The allow_changes property is an important addition to Versium for Valkyrie that is intended to allow Valkyrie plugins to support p2p file systems. Contributions and suggestions for implementing Secure Scuttlebutt and Dat plugins are welcome

Creating a new instance

A new instance of the implementation is created by a function called "new()". This function can take parameters, which are implementation-specific. Note that new() does not create any storage system (such as a database). It creates an Lua object that represents a connection to a storage system

For instance:

local valkyrieimplementation = require(modulename) local myvalkyrieinstance = valkyrie_implementation.new(params)

The argument “params” is a table, the contents of which are specific to the plugin implementation

Methods

This is an overview of methods for implementers, but a more complete resource is required. The Freya library is likely the primary consumer of this API for the foreseeable future, so these methods are not likely to be used directly by other software

Node Exists

Once the client creates an instance, it interacts with the storage system using this instance

node_exists(id)

Returns true or false depending on whether there is a node with this ID

Get Node History

This Versium method is not part of the Valkyrie API. In Valkyrie, a node represents a delta, not a version

Get Node Info

getnodeinfo(id)

Returns the data stored in the node as a table. Returns nil if the node doesn’t exist. Throws an error if anything else goes wrong

data = getnodeinfo("Foo")

After that “data” will be a table set to the content of the node in the format supplied at node creation

Get Node

Returns the contents of the data attribute of the node as a text string

data = get_node("Foo")

Create Node

Creates a node with the supplied parameters and returns the id

id = create_node(params, save)

The “params” are those required by the instance as defined at creation of the instance. The “save” is a boolean describing whether the object is immediately persisted

Get Node IDs - TO-DO

This is a paged interface for fetching nodes according to a criteria. It would probably be a handy feature to have, but it’s important to establish an understanding of indexing structures available in more of the target media before designing this interface