Unable to configure Gaxios options for common AuthClients

[benasher44]

Is your feature request related to a problem? Please describe.
For OAuth2Client for example, there's no way to configure the agent to make use of keep alive.

Describe the solution you'd like
Ideally, the constructor for all AuthClient sub-classes accept options that would be passed to gaxios, which would allow setting the agent

Describe alternatives you've considered
I think one could maybe overwrite the transporter ivar with one that is sub-classes to set an agent, but that feels bad.

Additional context
Nearly all of the API wrappers in https://github.com/googleapis/google-api-nodejs-client use a similar constructor pattern, wherein all of the constructor options are a subset of gaxios options.

[benasher44]

For some reason, the JWT class does this, but OAuth2Client doesn't. I think this also means that if JWT isn't overriding everything and you set gaxios options, behavior will be inconsistent, when calling non-overridden methods.

[benasher44]

Oh never mind; it looks like I had the types for JWT's constructor wrong. It doesn't accept gaxios options.

[danielbankhead]

Hey @benasher44,

Today, we offer a few options for setting keepAlive:

• 1: On a per-request basis
  

  google-auth-library-nodejs/samples/keepalive.js

  Lines 41 to 44 in dd04fbd

  	const agent = new https.Agent({keepAlive: true});
  	// use the agent as an Axios config param to make the request
  	const res = await client.request({url, agent});

• 2: You can assign your own Transporter to the AuthClient
  

  google-auth-library-nodejs/src/transporters.ts

  Lines 29 to 31 in dd04fbd

  	export interface Transporter {
  	request<T>(opts: GaxiosOptions): GaxiosPromise<T>;
  	}

  
  

  google-auth-library-nodejs/src/auth/authclient.ts

  Lines 87 to 96 in dd04fbd

  	export abstract class AuthClient
  	extends EventEmitter
  	implements CredentialsClient
  	{
  	/**
  	* The quota project ID. The quota project can be used by client libraries for the billing purpose.
  	* See {@link https://cloud.google.com/docs/quota| Working with quotas}
  	*/
  	quotaProjectId?: string;
  	transporter: Transporter = new DefaultTransporter();

Describe the solution you'd like
Ideally, the constructor for all AuthClient sub-classes accept options that would be passed to gaxios, which would allow setting the agent

This is a worthwhile feature request, we'll explore this as an option.

[danielbankhead]

Exposing this as a new option via:

• feat: Unify Base AuthClient Options #1663

Now all AuthClients can accept a gaxios, custom transporter instance, or set default properties for the transporter.

Additionally, it can be set for any AuthClient that would be instantiated via:

new GoogleAuth({
  clientOptions: {
    transporterOptions: {} // `GaxiosOptions`
  }
})