Set up two servers, one as a manager node and one as a worker node.
The worker node is labeled role_1=true .
The manager node is labeled role_2, role_3.
$ docker node update --label-add role_1=true node_1
node_1
$ docker node update --label-add role_2=true node_2
node_2
$ docker node update --label-add role_3=true node_2
node_2
$ docker node inspect node_1 --pretty
ID: rdnmlf1m0ge
Labels:
- role_1=true
$ docker node inspect node_2 --pretty
ID: td1cq8oxxrk2a
Labels:
- role_2=true
- role_3=true
The main.go file, Dockerfile is:
main.go
package main
import (
"net/http"
)
func main() {
http.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
w.Write([]byte("Hello World!"))
})
err := http.ListenAndServe(":8080", nil)
if err != nil {
return
}
}
dockerfile
FROM golang:latest
ENV GO111MODULE=off
WORKDIR /go/src/app
COPY . /go/src/app
RUN go build -o simple_program
ENTRYPOINT ["/go/src/app/simple_program"]
Write docker-compose file as below. Add only the label of the manager node to constraints .
version: '3.7'
services:
api_server:
image: simple_program
deploy:
mode: global
placement:
constraints:
- node.labels.role_2 == true
- node.labels.role_3 == true
ports:
- 8080:8080
It works as expected.
$ docker stack deploy --compose-file docker-compose.yml simple_http_server
Creating network simple_http_server_default
Creating service simple_http_server_api_server
$ docker service ls
ID NAME MODE REPLICAS IMAGE PORTS
2vksfee0e4ef simple_http_server_api_server global 1/1 simple_program:latest *:8080->8080/tcp
If it is distributed to both the manager node and the worker node or distributed only to the worker node, the service does not come up.
version: '3.7'
services:
api_server:
image: simple_program
deploy:
mode: global
placement:
constraints:
- node.labels.role_1 == true
- node.labels.role_3 == true
ports:
- 8080:8080
$ docker service ls
ID NAME MODE REPLICAS IMAGE PORTS
rhto667wd9lb simple_http_server_api_server global 0/0 simple_program:latest *:8080->8080/tcp
Nothing shows up in service logs either.
$ docker service ps --no-trunc simple_http_server_api_server
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
$ docker service logs simple_http_server_api_server
$
I read the stackoverflow questions and answers below, but it didn't help.
