This is a DNS resolver extension for k6. It allows you to resolve DNS names to IP addresses in your k6 scripts.

This extension was designed with the following goals in mind:

• Assert the performance of custom DNS servers under load.
• Provide a way to resolve DNS names to IP addresses using a specific DNS server in k6 scripts.

This extension provides two functions:

• dns.resolve() - resolves a DNS name to an IP address using the provided DNS server.
• dns.lookup() - resolves a DNS name to an IP address using the system's default DNS server.

To use this extension requires using the xk6 tool to build a custom k6 binary that includes the extension. You can install the extension using the following command:

xk6 build --with github.com/grafana/xk6-dns

From there we can use the bustom built binary to run the following example script:

import dns from 'k6/x/dns';

export const options = {
    vus: 10,
    duration: 200,
};

export default async function() {
    // Request the IP address of k6.io from the selected namerserver A records.
    const resolvedIP = await dns.resolve('k6.io', 'A', '9.9.9.9:53');
    console.log(`k6.io IPs as resolved against the 9.9.9.9 nameserver: ${resolvedIP}`);
    
    // Lookup the IP address of k6.io using the system's default DNS server.
    const lookupIP = await dns.lookup('k6.io');
    console.log(`k6.io IP as looked up by the system's default DNS server: ${lookupIP}`);
}

          /\      |‾‾| /‾‾/   /‾‾/
     /\  /  \     |  |/  /   /  /
    /  \/    \    |     (   /   ‾‾\
   /          \   |  |\  \ |  (‾)  |
  / __________ \  |__| \__\ \_____/ .io

     execution: local
        script: example.js
        output: -

     scenarios: (100.00%) 1 scenario, 10 max VUs, 10m30s max duration (incl. graceful stop):
              * default: 200 iterations shared among 10 VUs (maxDuration: 10m0s, gracefulStop: 30s)


     data_received.............: 0 B 0 B/s
     data_sent.................: 0 B 0 B/s
     dns_lookup_duration.......: avg=5.9ms  min=0s    med=3.5ms  max=44ms    p(90)=9.1ms   p(95)=11.69ms
     dns_lookups...............: 20  84.316677/s
     dns_resolution_duration...: avg=4.95ms min=2ms   med=3ms    max=31ms    p(90)=6.6ms   p(95)=12.94ms
     dns_resolutions...........: 20  84.316677/s
     iteration_duration........: avg=11.8ms min=2.1ms med=8.45ms max=76.46ms p(90)=17.21ms p(95)=23.16ms
     iterations................: 200 843.166766/s


running (00m00.2s), 00/10 VUs, 200 complete and 0 interrupted iterations
default ✓ [======================================] 10 VUs  00m00.2s/10m0s  200/200 shared iters

Resolves a DNS name to an IP address using the provided DNS server. It returns an array of IP addresses.

The query parameter is the DNS name to resolve, the recordType parameter is the type of DNS record to query for (e.g. 'A', 'AAAA', 'CNAME', 'NS', and 'PTR'), and the options parameter is an object that can contain the following properties:

• nameserver - the IP address and port of the DNS server to query. It should be in the format ip:port. If not provided, the system's default DNS server will be used.

Using the dns.resolve() operation will emit the following metrics:

• dns_resolutions: a Counter metric tracking the number of DNS resolutions performed.
• dns_resolution_duration: a Trend metric tracking the time taken to resolve the DNS.

Lookups a host name using the system's default DNS server. It returns an array of IP addresses.

The host parameter is the DNS name to resolve.

Using the dns.lookup() operation will emit the following metrics:

• dns_lookups: a Counter metric tracking the number of DNS lookups performed.
• dns_lookup_duration: A Trend metric tracking the time taken to lookup the DNS.

Contributions are welcome! If the module is missing a feature you need, or if you find a bug, please open an issue or a pull request. If you are not sure about something, feel free to open an issue and ask.