Config/Annotations: `proxy-busy-buffers-size` keeps NGINX from starting.

[Viswajith96]

After upgrading to latest helm release, nginx controller pods are failing to start with below error

Error: exit status 1
2025/07/08 04:29:35 [emerg] 42#42: "proxy_busy_buffers_size" must be less than the size of all "proxy_buffers" minus one buffer in /tmp/nginx/nginx-cfg3624499848:26103
nginx: [emerg] "proxy_busy_buffers_size" must be less than the size of all "proxy_buffers" minus one buffer in /tmp/nginx/nginx-cfg3624499848:26103
nginx: configuration file /tmp/nginx/nginx-cfg3624499848 test failed

-------------------------------------------------------------------------------
E0708 04:29:35.376699       7 queue.go:131] "requeuing" err=<

        -------------------------------------------------------------------------------
        Error: exit status 1
        2025/07/08 04:29:35 [emerg] 42#42: "proxy_busy_buffers_size" must be less than the size of all "proxy_buffers" minus one buffer in /tmp/nginx/nginx-cfg3624499848:26103
        nginx: [emerg] "proxy_busy_buffers_size" must be less than the size of all "proxy_buffers" minus one buffer in /tmp/nginx/nginx-cfg3624499848:26103
        nginx: configuration file /tmp/nginx/nginx-cfg3624499848 test failed

[atalakey4work]

I noticed the same issue. It happens when nginx.ingress.kubernetes.io/proxy-buffer-size is set, but nginx.ingress.kubernetes.io/proxy-busy-buffers-size is not, so it defaults to 8k. This causes problems, which didn’t occur in previous versions. It seems like the behavior has changed recently, and now both annotations need to be configured together to avoid issues.

[insider89]

Have same issue. What is value better to set for proxy-busy-buffers-size?

[PRYeswanthReddy]

same issue for us also, where we have the below annotation set at the ingress level, so the proxy-busy-buffers-size will be set same as the proxy-buffer-size?

Error reloading NGINX: ------------------------------------------------------------------------------- Error: exit status 1 2025/07/08 06:33:51 [warn] 37#37:
duplicate MIME type "application/xml" in /tmp/nginx/nginx-cfg2774865945:92 nginx: [warn] duplicate MIME type "application/xml" in /tmp/nginx/nginx-cfgXXXX5945:92 2025/07/08 06:33:51 [emerg] 37#37:
"proxy_busy_buffers_size" must be equal to or greater than the maximum of the value of "proxy_buffer_size" and one of the "proxy_buffers" in /tmp/nginx/nginx-cfg27XXXX45:488088 nginx: [emerg] "proxy_busy_buffers_size"
must be equal to or greater than the maximum of the value of "proxy_buffer_size" and one of the "proxy_buffers" in /tmp/nginx/nginx-cfg2XXXX45:488088 nginx: configuration file /tmp/nginx/nginx-cfg2XXXX5945 test failed

nginx.ingress.kubernetes.io/proxy-buffer-size: 128k

[toredash]

To fix this, set proxy-busy-buffers-size equal or larger than proxy-buffers-size:

Example, I had this set on at the controller level:

proxy-buffer-size: "32k"

To fix it, one have to add the proxy-busy-buffers-size size, as the default value is 8k:

proxy-busy-buffers-size: "32k"
proxy-buffer-size: "32k"

[pawgajda-drs]

I noticed the same issue. It happens when nginx.ingress.kubernetes.io/proxy-buffer-size is set, but nginx.ingress.kubernetes.io/proxy-busy-buffers-size is not, so it defaults to 8k. This causes problems, which didn’t occur in previous versions. It seems like the behavior has changed recently, and now both annotations need to be configured together to avoid issues.

Same here. Setting proxy-busy-buffers-size solves the issue.
This didn't cause me issues in previous releases as well (I upgraded from 1.11.x to 1.12.x last week).

I propose to make a note in changelog each time such change happens. I read the changelog before updating the controller and expected no issues, I was met by unpleasant surprise at the end.

[clevandowski]

I made different test, and it seems that the nginx controller is not able to reload config if proxy-buffer-size exceeds 16k (with proxy-buffers-number=4) and proxy-busy-buffers-size exceeds 16k

If I set bigger values, I still get error

nginx: [emerg] "proxy_busy_buffers_size" must be less than the size of all "proxy_buffers" minus one buffer in /tmp/nginx/nginx-cfg......

[pawgajda-drs]

I made different test, and it seems that the nginx controller is not able to reload config if proxy-buffer-size exceeds 16k (with proxy-buffers-number=4) and proxy-busy-buffers-size exceeds 16k

If I set bigger values, I still get error

nginx: [emerg] "proxy_busy_buffers_size" must be less than the size of all "proxy_buffers" minus one buffer in /tmp/nginx/nginx-cfg......

Weird. These are my settings on 1.13.0:

    proxy_buffering: true
    proxy-body-size: 0
    proxy-buffer-size: 256k
    proxy-busy-buffers-size: 256k
    proxy-buffers-number: 4
    proxy_ssl_verify: true
    proxy_connect_timeout: 5s;                                                                   
    proxy_send_timeout: 60s;                                                                  
    proxy_read_timeout: 60s; 

[clevandowski]

Ok sorry, I have dozen and dozen of ingresses, and I missed that one set proxy-buffer-size to 8k, so nginx controller could not set proxy-busy-buffers-size to a value > 16k

Now that I fix that, I can set proxy-buffer-size and proxy-busy-buffers-size to... 4096k
Dont think it's really useful ^^ but it was the value already defined, and I do not want to break something

[crinjes]

#12433 broke this. When proxy_busy_buffers_size is unset, the value normally is dynamically calculated. This change introduced a fixed value. There needs to be a warning or check that if nginx.ingress.kubernetes.io/proxy-buffer-size is changed, nginx.ingress.kubernetes.io/proxy-busy-buffers-size probably needs to be adjusted accordingly as well. I don't know the exact calculation for the valid range of the latter.

According to: https://github.com/nginx/nginx/blob/release-1.27.1/src/http/modules/ngx_http_proxy_module.c#L3531-L3564

• the default is 2 * max(proxy_buffer_size, proxy_buffers[size])
• the range is max(proxy_buffer_size, proxy_buffers[size]) <= proxy_busy_buffers_size <= (proxy_buffers[count]-1)*proxy_buffers[size]