Storage and Transport

Blocks of encoded ERIS content can be stored and transported in and over various formats and protocols (see also the section on storage and transport layers in the ERIS specification <http://purl.org/eris#name-storage-and-transport-layer> ).

The eris.Store class provides the generic abstraction over such storage and transport layers. You may use this to create your own bindings to some storage or transport layer.

A few useful storage and transport layers are provided by this library.

CoAP

The Constrained Application Protocol (CoAP) as defined in RFC 7252 <https://www.rfc-editor.org/rfc/rfc7252> is a transport protocol designed for constraint environments. It is light-weight, flexible enough and performant enough to use as a reliable transport protocol for ERIS encoded blocks. See also ERIS over CoAP <https://eris.codeberg.page/eer/coap.xml>.

This library provides an eris.Store implementation that can connect to a store via CoAP as well helpers to implement a store that is reachable via CoAP.

Blocks can be accessed and stored using the eris.coap.Store class:

eris.coap.Store(url)

A ERIS store that is connected via CoAP

Server

The function eris.coap.add_store_resources can be used to add all store resources to an aiocoap.resource.Site:

eris.coap.add_store_resources(site, store, path=['.well-known', 'eris'])

Adds CoAP resources to implement an ERIS CoAP store

Parameters

• site (aiocoap.resource.Site) – Site to add resources to.

• store (eris.Store) – Underlying block store.

• path (list(str)) – URL path to ERIS CoAP store (defaults to [‘.well-known’, ‘eris’]).

This can be used to start an ERIS CoAP store listening on TCP port 5683:

import eris.coap
import asyncio
import aiocoap


async def main():

    # create a dict store
    dict_store = eris.DictStore()

    # setup the CoAP site
    root = aiocoap.resource.Site()

    # Add the ERIS store resources, using the dict_store as underlying store
    eris.coap.add_store_resources(root, dict_store)

    # start the server
    await aiocoap.Context.create_server_context(
        root, bind=("127.0.0.1", 5683), transports=["tcpserver"]
    )

    # Run forever
    await asyncio.get_running_loop().create_future()


asyncio.run(main())

Note

The CoAP server currently does not support block-wise transfer <https://datatracker.ietf.org/doc/html/rfc7959>. This may be required when transporting blocks over UDP as the MTU of UDP may be smaller than the size of single ERIS block. Users are currently advised to use CoAP over TCP <https://www.rfc-editor.org/rfc/rfc8323> (as shown in example above).