apollo-datasource-rest: dynamic baseurl

[danilobuerger]

It would be nice to specify a dynamic baseurl for a RESTDataSource to be able to use fx consul srv entries.

[evans]

@danilobuerger hmm interesting, I'm not sure I follow. How do you set the url dynamically? What information would it depend on?

The other option is to set baseUrl to '' and then inside of get put the full url.

@martijnwalraven might be interested as well.

[martijnwalraven]

This is already supported by using a getter instead of setting the baseURL property directly. Something like:

  get baseURL() {
    if (this.context.environment === 'development') {
      return 'https://dev.example-api.com';
    } else {
      return 'https://prod.example-api.com';
    }
  }

Would that work for your use case? Not sure how Consul SRV entries fit into this. What makes them dynamic? What are they based on?

[danilobuerger]

Hi @evans and @martijnwalraven ! Thanks for responding, I should probably have been more specific. Sorry about that. What I would like to do is something like (shortened):

function baseURL(path: string, params?: URLSearchParamsInit, init?: RequestInit) {
  return new Promise<string>((resolve, reject) => {
    dns.resolveSrv(path.split("/")[1] + ".service.consul", (err, addresses) => {
      err ? reject(err) : resolve("http://" + addresses[0].name + ":" + addresses[0].port);
    });
  });
}

Basically return a promise that would resolve to a base url based on the supplied params. In case of consul one could for example use part of the path to get the name of a microservice to resolve its srv to get its (possible load balanced, round robin, etc.) address.

[martijnwalraven]

@danilobuerger Hmmm, we could make it possible to return a promise from the baseURL getter, that would make it possible to resolve the record to get the host and port.

But why does the URL need to depend on the path, params or other call-specific information? Couldn't you just define a data source per microservice?

You also probably wouldn't want to resolve for every call, that seems like quite a bit of overhead?

[danilobuerger]

True, this was just an example in brevity. You could cache the result for example or track a round robin on the returned addresses. For this specific example, you could probably get away with defining it per microservice and not having to rely on the path. I included path, params, init in the example above because those are in context anyway when baseURL is currently getting called and I bet some other guy will come along and needing it for some use case we haven't thought of once (if) returning a promise is possible.

[martijnwalraven]

@danilobuerger I experimented some and came up with 2e6073d#diff-94c74c4c5e5f1e69b942b0b56a962852R133. Not sure if it is worth the complexity, but curious what you think.

[godspeedelbow]

+1 I need to poll a configuration server first before I know baseURL, so it would be great if the baseURL getter can return a Promise. Otherwise, I have to postpone instantiating ApolloServer until I have resolved the baseURL value

[danilobuerger]

@martijnwalraven Awesome work! Line read looks good. Concept makes sense.

[martijnwalraven]

@danilobuerger @godspeedelbow I incorporated the feedback and opened a PR with a discussion and some questions. Your input is appreciated! #1277

[danilobuerger]

Fixed in #1277