Hey, I’m using ktor-client-cio and trying to figure out if there is anyway to change dns resolver in...

# ktor

[André Martins]

Hey, I’m using ktor-client-cio and trying to figure out if there is anyway to change dns resolver instead of using java network, I need to setup a timeout for the resolution and a retry count. Any ideias on where to look? (Seen this)

[Aleksei Tirman [JB]]

I think it's impossible for CIO engine.

[André Martins]

I’ve worked it out by creating a feature that intercepts before Engine phase on the sendPipeline and performs the resolution

[Aleksei Tirman [JB]]

Could you please share a code snippet?

[André Martins]

Ya sure

override fun install(feature: DnsResolverFeature, scope: HttpClient) {
    scope.sendPipeline.insertPhaseBefore(HttpSendPipeline.Engine, DNSResolve)
    scope.sendPipeline.intercept(DNSResolve) {
        val host = context.host
        repeat(retries) {
            try {
                val addr = withTimeout(timeout) {
                    withContext(<http://Dispatchers.IO|Dispatchers.IO>) {
                        InetAddress.getByName(host)
                    }
                }

                context.host = addr.hostAddress
                return@repeat
            } catch (ex: TimeoutCancellationException) {
                <http://logger.info|logger.info>("Timeout occurred while resolving the IP address for host: $host")
                throw UnknownHostException(host)
            }
        }
    }
}

[André Martins]

Do you know how can I make sure ktor-client checks for stale connections?

[Aleksei Tirman [JB]]

While using your code the Host header in a request will contain an original hostname or an IP-address?

[André Martins]

I mean let me check

[André Martins]

Ya it takes the ip address, not sure in which phase it generates the headers

[Aleksei Tirman [JB]]

As I can see from the CIO engine implementation, you can manually pass a Host header.

[André Martins]

Ya doing that now