Adapters and Operations

Adapters are concrete implementations of DFM functionality. They are classes initialized with site and provider, with a single body() method that accepts input arguments and returns output.

Adapter Structure

from dfm.exec import Site, Provider

class MyNewAdapter:
    def __init__(self, site: Site, provider: Provider | None):
        self._site = site
        self._provider = provider

    async def body(self, param_1: Any, local_param: str) -> Any:
        # body implementation
        return output

Adapters versus Operations

• Adapters — created by adapter developers; maintained and tested separately. DFM users do not interact with adapters directly.

• Operations — the public API. Users call operations in their pipelines and apps. Operations define how adapters are exposed (or not) to federation or site users.

Adapters implement functionality; operations define the interface users see.

Defining Operations

All public operations are listed in the operations section of the configuration file (.dfm.yaml) and defined by the federation administrator:

operations:
  operation_package.UsersExposedOperation:
    description: "This is operations exposed to DFM users"
    parameters:
      param_1:
        description: "First parameter"
        type: _type_
    required:
      - param_1
    returns: _type_

Mapping Operations to Adapters

The site administrator maps public operations to adapters per site. When creating site configuration, they decide which:

• Public operations are available at the site

• Local adapter implements each operation

This mapping is defined in the sites section of the configuration file:

sites:
  my_site:
    interface:
      "#/operations/operation_package.UsersExposedOperation":
      adapter: adapters_dir.lib.my_adapter.MyAdapter
      args:
        param_1:
          from-param: param_1
        local_param:
          const: "Some site-specific param"

Parameter overloading: When mapping operations to adapters, the operation interface can be overloaded. In the example above, the public operation exposes only param_1, but the adapter’s body() requires two arguments. The extra parameter (local_param) is supplied using a constant. This gives site administrators flexibility in how operations are managed.

Standard Library

DFM includes adapter libraries with reusable schemas and example adapters as a starting point. Users are expected to write their own adapters tailored to their federation’s needs.