How to configure Nomad job for Selenium Grid - selenium

Question

I'm trying to setup a Selenium Grid in Hashicorp Nomad but I don't know how to make the networking work.
What I want is to have one selenium-hub and 8 chrome-nodes. I found that I can only have multiple allocations of the node-task if I put the node-task into its own group.
Running it locally, I would start the grid like this:
docker network create grid
docker run -d -p 4442-4444:4442-4444 --net grid --name selenium-hub selenium/hub:4
docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub -e SE_EVENT_BUS_PUBLISH_PORT=4442 -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 -v /dev/shm:/dev/shm selenium/node-chrome:4
docker run -d --net grid -e SE_EVENT_BUS_HOST=selenium-hub -e SE_EVENT_BUS_PUBLISH_PORT=4442 -e SE_EVENT_BUS_SUBSCRIBE_PORT=4443 -v /dev/shm:/dev/shm selenium/node-chrome:4
...
How do I need to configure Network for this to work?
My current job looks like this:
job "selenium" {
datacenters = ["dc1"]
type = "service"
group "selenium_hub" {
network {
}
task "selenium_hub" {
driver = "docker"
config {
image = "selenium/hub:4"
}
}
}
group "selenium_nodes" {
count = 8
network {
}
task "selenium_node" {
driver = "docker"
env {
SE_EVENT_BUS_HOST = "selenium-hub"
SE_EVENT_BUS_PUBLISH_PORT = "4442"
SE_EVENT_BUS_SUBSCRIBE_PORT = "4443"
}
config {
image = "selenium/node-chrome:4"
}
}
}
}

Answer 1

If anyone comes across this, I've got it working like this:
job "selenium" {
datacenters = ["dc1"]
type = "service"
group "selenium_hub" {
network {
mode = "host"
}
task "selenium_hub" {
driver = "docker"
config {
image = "selenium/hub:3.141.59-20201010"
network_mode = "host"
}
}
}
group "selenium_nodes" {
count = 8
network {
mode = "host"
port "http" {}
}
task "selenium_node" {
driver = "docker"
env {
HUB_HOST = "localhost"
SE_OPTS = "-port ${NOMAD_PORT_http}"
}
config {
network_mode = "host"
image = "selenium/node-chrome:3.141.59-20201010"
}
}
}
}
I used Selenium 3 instead of 4 because we also had other issues with 4.
Since I've used host network and all nodes use the port 5555 I needed to pass a dynamic port (http) to Selenium via SE_OPTS environment variable.