Support SRV records

Suppose we have multiple environments -- staging, production, development.

In each environment, we have a different redis server. However, I don't want to change the code of my application -- I want the application to connect to a host, redis-server, and have it reach the correct server. I can do this with CNAMEs. However, each server is running on a different port: staging, port 8362; production, port 19872; development, 6379. This is because we're using a hosting provider for our redis instances.

I still don't want to have to change the configuration or code to connect to the proper redis instance.

Enter DNS SRV records: the record contains a target and a port.
redis-server.staging.my-environment.com -> SRV 0 10 8362 redis-192.hosted.redis-provider.com (priority, weight, port, target [name])

I would like to be able to tell redis to connect to simply redis-server, allow the machine's searchdomains DNS list to expand that to redis-server.staging.my-environment.com, allow the redis connector to do a DNS lookup for the SRV record, and then connect to the appropriate server and port:

const client = createClient({
    url: 'redis://alice:foobar@redis-server'
  });

and with just the above, the infrastructure would control the reference to the redis server for that environment.

See also:

• https://nodejs.org/api/dns.html#dnsresolvesrvhostname-callback
• MongoDB "DNS Seedlist" connection format

Start by locating the createClient URL connection handling and review Node.js dns.resolveSrv, as referenced in the issue. Support redis:// hosts that resolve through SRV records, including the resolved target and port, and verify that the client connects to the environment-specific Redis server.