HAProxy peering in kubernetes - kubernetes

Question

Background
Due to our application needs to use sticky tables for a custom header, we decided to use HAProxy, our layout looks as follows:
Nginx Ingress -> HAproxy service -> headless services of stateful application
So far stickiness works fine, but there is a scenario where if handled by the other HAproxy replica, it fails. We are trying to use peers to address this problem.
I use bitnami helm chart to deploy it, this is my values file:
metadata:
chartName: bitnami/haproxy
chartVersion: 0.3.7
service:
type: ClusterIP
ports:
- name: http
protocol: TCP
port: 80
targetPort: 8080
- name: https
protocol: TCP
port: 443
targetPort: 8080
- name: peers
protocol: TCP
port: 10000
targetPort: 10000
containerPorts:
- name: http
containerPort: 8080
- name: https
containerPort: 8080
- name: peers
containerPort: 10000
configuration: |
global
log stdout format raw local0 debug
defaults
mode http
option httplog
timeout client 10s
timeout connect 5s
timeout server 10s
timeout http-request 10s
log global
resolvers default
nameserver dns1 172.20.0.10:53
hold timeout 30s
hold refused 30s
hold valid 10s
resolve_retries 3
timeout retry 3s
peers hapeers
peer $(MY_POD_IP):10000 # I attempted to do something like this
peer $(REPLICA_2_IP):10000 #
frontend stats
bind *:8404
stats enable
stats uri /
stats refresh 10s
frontend myfrontend
mode http
option httplog
bind *:8080
default_backend webservers
backend webservers
mode http
log stdout local0 debug
stick-table type string len 64 size 1m expire 1d peers hapeers
stick on req.hdr(MyHeader)
server s1 headless-service-1:8080 resolvers default check port 8080 inter 5s rise 2 fall 20
server s2 headless-service-2:8080 resolvers default check port 8080 inter 5s rise 2 fall 20
server s3 headless-service-3:8080 resolvers default check port 8080 inter 5s rise 2 fall 20
replicaCount: 2
extraEnvVars:
- name: LOG_LEVEL
value: debug
- name: MY_POD_IP
valueFrom:
fieldRef:
fieldPath: status.podIP
From what I read in HAProxy documentation, it requires the peers IP's, which in this case are the replicas IPs. However, the configmap does not allow injecting IPs from the HAProxy replicas.
I also thought of using a initContainer to modify the haproxy.cfg at deployment time with the correct IPs, but the volume is read-only and I would have to alter a fork of the chart to customize it.
If anyone has an idea of a different approach or workaround, I would appreciate the comments. Thanks!

Answer 1

...the configmap does not allow injecting IPs from the HAProxy replicas.
HAProxy's configuration supports environment variables. Eg. peer $(MY_POD_IP):10000 => peer ${MY_POD_IP}:10000