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Data fetching

HttpAgent allows you to isomorphically fetch data in IMA.js applications. It is a simple wrapper around native fetch with additional features like caching, proxy support and others.

Cancellable requests​

The HttpAgent has support for AbortController to cancel requests in native way. There are two ways you can provide custom instance of AbortController to the HttpAgent, where each has it's own benefits.

options.abortController​

Using this approach has the added benefit of HttpAgent being able to additionally reuse this controller for cancelation of timeout requests.

const controller = new AbortController();

httpAgent.get('<uri>', '<data>', {
  abortController: controller,
});

// Cancel the request
controller.abort();
info

If you don't provide custom instance of AbortController the agent uses it's own instance internally to cancel running timeout requests.

options.fetchOptions.signal​

This approach is more similar to native fetch definition. However since currently you can only provide one signal to fetch request and we don't have access to the controller instance (from within the HttpAgent), we are unable to abort time out requests in this case.

const controller = new AbortController();

httpAgent.get('<uri>', '<data>', {
  fetchOptions: {
    signal: controller.signal,
  }
});

// Cancel the request
controller.abort();
note

The time out requests still throw the same timeout error, however they are not canceled (aborted). This is the only difference between the two forementioned methods.

Caching failed requests​

As well as normal caching, HttpAgent also supports caching of failed requests using the cacheFailedRequest option. When enabled, the agent will cache the error when a request fails, and for each subsequent request with the same parameters, it will return the cached error response until the cache expires.

The cacheFailedRequest option is disabled by default. You can enable it likewise:

httpAgent.get('<uri>', '<data>', {
    cacheFailedRequest: true,
});

This option is useful to keep the responses consistent throughout the server and client side, and by that prevent mishmash-dom errors, when the page renders differently on server and client.