The Transport Protocol

The SDK uses axios library internally to perform HTTP calls. This can be customized and one can use any other (async) protocol, which is implemented in the transport.js file.

The transport protocol defines

• What is an HTTP request
• What is the corresponding response
• How errors are handled

The transport protocol exports a single asynchronous function request which takes two parameters.

The first parameter is the request object with the following attributes. Note that it matches axios requests.

• method is the HTTP verb
• url is the URL to call
• headers is an object containing key value pairs with http headers and their values
• data is the request payload

The second parameter is an set of additional parameters that have been pushed down to the transport layer (see the Pushdown paragraph for more details). In particular, the timeout and AbortSignal parameters should be honored by the transport layer.

If the request is successful, a promise is returned with the result payload, as a string.

If the request fails, the promise is rejected with an error object either having class HttpError or AbortError

HttpError class has the following attributes:

• statusCode is the HTTP status code, such as 404, 500, etc.
• statusText is the HTTP status text coming with the error
• data is the response data, if any

For proper error handling by the ACC SDK, it's important that the actual class of returned objects is named either HttpError or AbortError

The transport can be overriden by using the client.setTransport call and passing it a transport function, i.e. an async function which

• Takes a Request object literal as a parameter
• Returns a the request result in a promise
• Returns a rejected promise containing an HttpError in case of failure