Protocol plugins

Protocol plugins is a new feature of DLite that allow a clear separation between serialising/parsing DLite instances to/from external data representations and transferring data to/from external data resources. This is illustrated in the Figure below.

It allows to mix and match different protocol and storage plugins, thereby reducing the total number of plugins that has to be implemented.

For example can you combine a bson storage plugin with the file, http or sftp protocols to load an instance stored as BSON, from a file, a website or a SFTP server, respectively.

The dlite.Instance Python class, provides a simple interface to protocol and storage plugins via the dlite.Instance.load() class method and the dlite.Instance.save() method.

Examples

Accessing a YAML file using the http protocol:

    >>> url = "https://raw.githubusercontent.com/SINTEF/dlite/refs/heads/master/storages/python/tests-python/input/test_meta.yaml"
    >>> dlite.Instance.load(protocol="http", driver="yaml", location=url)

Directly access to protocols

Protocol plugins can also be accessed in Python via the Protocol class.

In the example below the data b"hello world" is first saved to the file hello.txt and then loaded back again:

    >>> with Protocol(protocol="file", location="hello.txt", options="mode=rw") as pr:
    ...     pr.save(b"hello world")
    ...     s = pr.load()
    >>> s
    b'hello world'

Note that all data are bytes objects.

Creating protocol plugins

Currently, DLite is shipped with the following protocols: file, http, sftp. New protocols will be available if the path to the directory is added to the dlite.python_protocol_plugin path variable.

Please see the existing plugins, for how to implement a new plugin.