Solution for Docker Swarm external verification load balancing not taking effect

Problem Description

I created three virtual machines with centos7 installed locally and initialized the swarm cluster, namely one manager node and two worker nodes; the IP addresses of the three machines are 192.168.124.8 - (manager節點) , 192.168.124.9 - (worker節點) , 192.168.124.10 - (worker節點)

[root@localhost ~]# docker node ls
ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION
j0f4up8v7epacp3vceby4exsz localhost.localdomain Ready Active 19.03.13
qeeqc10gl9e56w61pajjqle08 localhost.localdomain Ready Active 19.03.13
r5sg5m9dkwcu76t56hg0vu29t * localhost.localdomain Ready Active Leader 19.03.14

Then I started a service on the swarm cluster with the following command

docker service create --name test-vote --replicas 2 --constraint node.role==worker --publish 8080:80 registry.cn-hangzhou.aliyuncs.com/anoy/vote

Directly curling the worker node ip:port can get a response, but the returned containerId remains unchanged, and if you directly access the manager node, you will not get a response, it seems that the load balancing is not effective!

solve

After some searching, I found the answer on stack overflow: https://stackoverflow.com/questions/48360577/docker-swarm-mode-routing-mesh-not-working

It turned out to be a firewall issue. According to the documentation, in order for swarm mode routing mesh to take effect, tcp/udp port 7946 and udp port 4789 must be opened before initializing the swarm cluster. https://docs.docker.com/engine/swarm/ingress/

So if it is centos, you can use the following script to open the port. Each host in the swarm cluster needs to be opened. For convenience, both TCP and UDP ports are opened. After opening the port, you need to restart the machine.

firewall-cmd --permanent --zone=public --add-port=4789/tcp && \
firewall-cmd --permanent --zone=public --add-port=7946/tcp && \
firewall-cmd --permanent --zone=public --add-port=4789/udp && \
firewall-cmd --permanent --zone=public --add-port=7946/udp && \
firewall-cmd --reload && \
# Reboot sudo reboot

This is the end of this article about docker swarm external verification load balancing not taking effect. For more relevant docker swarm load balancing content, please search 123WORDPRESS.COM's previous articles or continue to browse the following related articles. I hope everyone will support 123WORDPRESS.COM in the future!