Increase URL length limit for K8S ingress - http

Question

I have a GET request URL into a service on my kubernetes that's ~9k long and it seems like the request is getting stuck in Kubernetes's ingress. When I tried calling the url from within the docker or from other docker in the cluster it works fine. However when I go through a domain name I'm getting the following response header:

Answer 1

I think the parameter you must modify is Client Body Buffer Size
Sets buffer size for reading client request body per location. In case
the request body is larger than the buffer, the whole body or only its
part is written to a temporary file. By default, buffer size is equal
to two memory pages. This is 8K on x86, other 32-bit platforms, and
x86-64. It is usually 16K on other 64-bit platforms. This annotation
is applied to each location provided in the ingress rule
nginx.ingress.kubernetes.io/client-body-buffer-size: "1000" # 1000 bytes
nginx.ingress.kubernetes.io/client-body-buffer-size: 1k # 1 kilobyte
nginx.ingress.kubernetes.io/client-body-buffer-size: 1K # 1 kilobyte
nginx.ingress.kubernetes.io/client-body-buffer-size: 1m # 1 megabyte
So you must add an annotation to your nginx ingress config.

Answer 2

In my case, I had to set http2_max_header_size and http2_max_field_size in my ingress server-snippet annotation. For example:
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
annotations:
nginx.ingress.kubernetes.io/server-snippet: |
http2_max_header_size 16k;
http2_max_field_size 16k;
I was getting ERR_CONNECTION_CLOSED and ERR_FAILED in Google Chrome and "empty response" using curl, but the backend would work if accessed directly from the cluster network.
Assigning client-header-buffer-size or large-client-header-buffers in the ingress controller ConfigMap didn't seem to work for me either, but I realized that curl would do it if using HTTP 1.1 (curl --http1.1)

Answer 3

Find the configmap name in the nginx ingress controller pod describition
kubectl -n utility describe pods/test-nginx-ingress-controller-584dd58494-d8fqr |grep configmap
--configmap=test-namespace/test-nginx-ingress-controller
Note: In my case, the namespace is "test-namespace" and the configmap name is "test-nginx-ingress-controller"
Create a configmap yaml
cat << EOF > test-nginx-ingress-controller-configmap.yaml
kind: ConfigMap
apiVersion: v1
metadata:
name: test-nginx-ingress-controller
namespace: test-namespace
data:
large-client-header-buffers: "4 16k"
EOF
Note: Please replace the namespace and configmap name as per finding in the step 1
Deploy the configmap yaml
kubectl apply -f test-nginx-ingress-controller-configmap.yaml
Then you will see the change is updated to nginx controller pod after mins
i.g.
kubectl -n test-namespace exec -it test-nginx-ingress-controller-584dd58494-d8fqr -- cat /etc/nginx/nginx.conf|grep large
large_client_header_buffers 4 16k;
Thanks to the sharing by NeverEndingQueue in How to use ConfigMap configuration with Helm NginX Ingress controller - Kubernetes