How to chain multiple agents, dispatchers, and interceptors??

[SukkaW]

I noticed that there are many useful built-in agents/dispatchers/interceptors. I'd like to enable EnvHttpProxyAgent and RetryAgent both at once. I also want to enable automatic redirect and custom response error (and HTTP caching when it lands in the future) with interceptors, while enabling DNS lookup caching through cacheable-lookup.

I am also a fan of fetch. How do I create a fetch function with all those features enabled?

[mcollina]

The Agent has a compose function for this purpose. Set the resulting value as the globalDispatcher.

[SukkaW]

The Agent has a compose function for this purpose. Set the resulting value as the globalDispatcher.

Thanks for your reply!

I know compose exists. From what I see, compose is part of Dispatcher, while Agent extends Dispatcher. However, Dispatcher#compose accepts the Dispatcher.DispatcherComposeInterceptor[] type, but I can't see any Agent (EnvHttpProxyAgent for example) using that Dispatcher.DispatcherComposeInterceptor type.

Also there are RetryAgent (as an Agent) and retry interceptor, which one is recommended though?

[mcollina]

there is a retry interceptor you can use. We should be deprecate and remove the retryagent.

[SukkaW]

Thanks! I am able to create a global dispatcher:

const agent = new EnvHttpProxyAgent({
  allowH2: true,
  connect: {
    lookup(hostname, opt, cb) {
      return cacheableLookup.lookup(hostname, opt as CacheableLookupOptions, cb);
    }
  }
});

setGlobalDispatcher(agent.compose(
  interceptors.retry({
    maxRetries: 5,
    minTimeout: 10000
  }),
  interceptors.redirect({
    maxRedirections: 5
  }),
  interceptors.responseError({
    throwOnError: true
  })
));

According to my understanding, there should only be one Agent, no chained multiple Agent, is that right?

[mcollina]

yes, exactly.

[metcoder95]

You can also use the dns interceptor with a custom lookup; it requires some adjustments but overall through the interceptors you should be able to achieve the different strategies you highlighted here

[mbrevda]

We should be deprecate and remove the retryagent

can you elaborate on that? Will the retry agent be removed from undici?