External adapters are added to the Chainlink node by creating a bridge type. Bridges define the task's name and URL of the external adapter. When a task type is received that is not one of the core adapters, the node will search for a bridge type with that name, utilizing the bridge to your external adapter. Bridge and task type names are case insensitive.

To create a bridge on the node, you can navigate to the "Create Bridge" page in the GUI. From there, you will specify a Name, URL, and optionally the number of Confirmations for the bridge.

The Bridge Name should be unique to the local node, and the Bridge URL should be the URL of your external adapter, whether local or on a separate machine.

To add jobs which use the bridge, simply give their bridge name to the task type, as shown below for the randomNumber type.

{
  "initiators": [
    { "type": "runLog" }
  ],
  "tasks": [
    { "type": "randomNumber" },
    { "type": "copy",
      "params": {"copyPath": ["details", "current"]}},
    { "type": "multiply",
      "params": {"times": 100 }},
    { "type": "ethuint256" },
    { "type": "ethtx" }
  ]
}

Since randomNumber is not a core adapter, it is an external adapter that each node on the request needs to have in order to fulfill the request. If you try to add a task type that does not exist already as a bridge, the job will fail to create.

You can also exclude extra parameters from the spec when creating the job. This will allow requesters the ability to specify them per-request:

{
  "initiators": [
    { "type": "runLog" }
  ],
  "tasks": [
    { "type": "randomNumber" },
    { "type": "copy" },
    { "type": "multiply" },
    { "type": "ethuint256" },
    { "type": "ethtx" }
  ]
}

Testing External Adapters and Bridges

The easiest way to test to see if you're external adapter is working, is to use a web job. You can read more about the web initiator here.

Let's say you have an external adapter called weather-cl-ea and it's registered in the bridges tab. It takes 1 parameter: city:boston, and in solidity, you'd pass the parameter with:

request.add("city","boston")

How can we test the adapter on our node?

The easiest way is to setup a web job and manually add the parameter.

{
  "name": "weather-cl-ea BOSTON",
  "initiators": [
    {
      "type": "web"
    }
  ],
  "tasks": [
    {
      "type": "weather_cl_ea",
      "params": {
        "city": "boston"
      }
    }
  ]
}

Adding the following:

"params": {
        "city": "boston"
      }

Manually sets the parameters, and is equivalent to using request.add as shown above, or adding the data in the --d if you're using curl.

There will be a big Run button on your job definition, just hit it to kick off the job.