Send head values as string

Grafana k6
1

Hi,

I found that k6 always sends the http headers’ value as an array of string. For example, if I send something like this:

http.get(`${url}/session`, { 
        'Content-Type': 'application/json',
        'Connection': "keep-alive"
    });

The server gets:

{
        "method": "GET",
        "url": "https://somewhere",
        "headers": {
            "User-Agent": [
                "k6/0.37.0 (https://k6.io/)"
            ],
            "Content-Type": [
                "application/json"
            ],
            "Connection": [
                "keep-alive"
            ],
        },
    }

Is it possible to make k6 send the values as simple string?

2

Hello!
That code should not result in those headers being set - the key=value pairs need to reside within the headers object like this:

http.get(`${url}/session`, { 
    headers: {
        'Content-Type': 'application/json',
        'Connection': "keep-alive"
    }
});

You probably just accidentally left it out of the code snippet though :slight_smile:

That JSON is actually what you’d see if you JSON.stringify the request headers. Here’s an example:

import http from 'k6/http';

export default function () {
  let res = http.get('https://test-api.k6.io/public/crocodiles/', {
    headers: {
      'Content-Type': 'application/json',
      'Connection': 'keep-alive',
    }
  });

  console.log(JSON.stringify(res.request.headers, null, 2));
}

Yields:

{
  "User-Agent": [
    "k6/0.37.0 (https://k6.io/)"
  ],
  "Content-Type": [
    "application/json"
  ],
  "Connection": [
    "keep-alive"
  ]
}

This is not actually what the server ends up seeing - those arrays do get flattened at some point (I think here, but I might need our devs to confirm that :sweat_smile:).

As a general HTTP debugging tip, using a web proxy might yield the most insight into what the server actually ends up seeing - they are great as they are in effect a 3rd party to the HTTP conversation so you know exactly what’s going across the wire and back.