[RFC] Detect system default resolver

[WyriHaximus]

As discussed in #29 a PR that detects the system default resolver on *nix systems.

[jsor]

#48 adds a TimeoutExecutor, would it make sense to read the timeout option from resolve.conf and use that value to create the TimeoutExecutor?

[WyriHaximus]

#48 adds a TimeoutExecutor, would it make sense to read the timeout option from resolve.conf and use that value to create the TimeoutExecutor?

Most certainly! If @reactphp/core likes the proposed external API I'll go more in depth and add more features like the timeout option 😄 .

[mailopl]

Any news on this guys? Any chance for it to being merged in next week?

[kelunik]

What's with Windows? This PR will result in many written apps not being able to run on Windows.

[WyriHaximus]

Ping @jsor@clue, what do you think about the public facing API? If you like it I'll work it out into something that also works on windows and has a default fallback so it works if detection fails.

[clue]

Thanks for filing this ticket @WyriHaximus, I'd love to get this feature in! 👍

I'm currently unsure about its API, but have you seen the (somewhat outdated) https://github.com/reactphp/dns/blob/master/src/Config/FilesystemFactory.php ?

I think it make more sense to keep this in a separate class and then pass the nameserver configuration to the default create*() methods.

What do you think about this?

[WyriHaximus]

@clue we could go with something like this, where 8.8.8.8 is used as a fallback:

$loop = React\EventLoop\Factory::create();
$factory = newReact\Dns\Resolver\Factory();
$dns = $factory->createCached(determineSystemDefaultServer('8.8.8.8'), $loop);

[kelunik]

I think it should use the first one, not a random one. I think the first one is considered the primary DNS and order should be respected in /etc/resolv.conf.

[kelunik]

There can be only one nameserver per nameserver config option in /etc/resolv.conf.

[kelunik]

man resolv.conf says it should default to the local nameserver if none are present, but Amp doesn't do this either, at least currently.

[kelunik]

I added some comments regarding the implementation.

While it will usually work to read /etc/resolv.conf once, the nameservers in there might change, e.g. because a software might be running on a notebook that changes the access point (WLAN).