WIP - imported from other module

[leftieFriele]

WIP - Creating an improved HTTP client which has a circuit breaker.

Note, these are just notes 😄

Todos

• identify the metrics on client which we need to continue having
• add metrics support
• add prometheus hook into opossum
• close the gap on features in client and this one.... not sure what those are yet.

Open questions ❓

• request which we are using here is single origin, which means that a request to https://google.com returning a location header with https://www.google.com will not redirect as it's a different host. the client implementation supports redirectable and it's used in the resolvers
• decide on default redirect behaviour
• decide on options surface, how much control should there be?
• should we rename this branch to alpha to create a release?
• do we add retries to the client?

Errors

If options.fallback is not set, we wrap errors in a HttpClientError class.

const client = new HttpClient();
try {
  await client.request(...)
} catch (err) {
 if (err instance of HttpClientError) {
  // do stuff
 }
}

Constructor options

abortController

we need to be able to cancel requests in opossum

followRedirects

if we should follow redirects or not, default behaviour is to not follow (???)

fallback

const client = new HttpClient({ fallback: function () { return 'We are down.' } });
// can also be set like this

client.fallback(function () { 'We are down'; });

Closes #11

[digitalsadhu]

So far, so good I reckon.

[digitalsadhu]

I feel like this timeout should be 1000. Wonder why @trygve-lie went for 500 🤔

[digitalsadhu]

I think for the Podium client, fallback as a string is more useful than fallback as a function.