Session Persistence using Traefik on Docker Swarm Replicas - docker

Question

I trying to implement sticky session on dockers-swarm with traefik, but I could not achieve session persistence over two replicas on same machine.
In my docker-compose.yml, I have added labels for traefik and added the loadbalancer as well. Below is my docker-compose.yml, (Although the indentation might not look proper here, but it correct in actual project)
version: '3'
services:
web:
image: php:7.2.11-apache-stretch
ports:
- "8080:80"
volumes:
- ./code/:/var/www/html/hello/
stdin_open: true
tty: true
deploy:
mode: replicated
replicas: 2
restart_policy:
condition: any
update_config:
delay: 2s
labels:
- "traefik.docker.network=docker-test_privnet"
- "traefik.port=80"
- "traefik.backend.loadbalancer.sticky=true"
- "traefik.frontend.rule=PathPrefix:/hello"
networks:
- privnet
loadbalancer:
image: traefik
command:
--docker \
--docker.swarmmode \
--docker.watch \
--web \
--loglevel=DEBUG
ports:
- 80:80
- 9090:8080
volumes:
- /var/run/docker.sock:/var/run/docker.sock
deploy:
restart_policy:
condition: any
mode: replicated
replicas: 1
update_config:
delay: 2s
placement:
constraints: [node.role == manager]
networks:
- privnet
networks:
privnet:
external: true
Am I missing anything?

Answer 1

A few things.
.sticky is deprecated in favor of traefik.backend.loadbalancer.stickiness=true
I don't think you need to set the network with traefik.docker.network when you only have a single network connected to that service.
Make sure you're testing with a tool that uses cookies, which is how sticky sessions stay sticky. If using curl, be sure to use -c and -b as in this example.
I used the voting app sample from my test Swarm setup and added sticky sessions to the "vote" service and it worked for me on a single node. If using a multi-node swarm you'll need the LB in front of multiple swarm nodes to also enable sticky.