Issue with kong.request.get_header and ngx.var.http_xxx returning nil in Kong 3.7

[zhou-cl]

Hi,

I’m experiencing an issue with Kong 3.7 where headers accessed via kong.request.get_header and ngx.var.http_xxx in the access phase are returning nil. As a result, when I try to set these headers using kong.service.request.set_header, they remain nil.

Could anyone explain why this might be happening? Are there specific handling steps I need to follow to resolve this issue?

Thank you!

[zhou-cl]

function axasd:access(conf)
    local bxxxx =  kong.request.get_header("axxxx")
    local c = "12312312312"
    kong.service.request.set_header('axxxx',c)
end

[zhou-cl]

@bungle @guanlan help

[zhou-cl]

In Kong 3.7, I am using the following Lua code:

local headers = ngx.req.get_headers()
local headerxxx= headers["xxx"]  
kong.service.request.set_header('xxxx', "111")

This works fine. However, when I change it to:

local headerxxx = ngx.var.http_xxx
kong.service.request.set_header('xxxx', "111")

it does not work. I would like to understand why this happens. Please explain the internal mechanism of Kong 3.7. In Kong 1.5.1, the previous code works correctly.

[zhou-cl]

I’m not sure where the issue lies:

local headers = ngx.req.get_headers()
local headerxxx = headers["xxx"]
kong.service.request.set_header('xxxx', "111")

This works fine. However, when I change it to:

local headerxxx = ngx.var.http_xxx
kong.service.request.set_header('xxxx', "111")

It does not work. I’m using the following log_format to check the logs:

log_format main '{'
    '"a": "$http_a",'
'}';

I’ve added this print statement in the post-function:

local a = kong.request.get_header("a")
if a ~= nil and a ~= '' then
    kong.response.set_header('response-a', a)
else
    kong.response.set_header('response-a', "a is null")
end

Can you help me identify the problem? I’m currently out of ideas.

[chobits]

nginx's log format $http_a may only log the original request header, I guess. You could try to capture the proxied request to see if the header is added or modified.

[zhou-cl]

But the two different methods yield different results. It’s quite frustrating.

[chobits]

Debugging this issue may be challenging and might require in-depth debugging in your own environment. I recommend using in-depth debugging methods, such as Nginx's debug logs or GDB, to help pinpoint the problem.

[zhou-cl]

thanks