Passing ENV variables does not work with docker-compose - docker

Question

I am struggling with passing ENV variables using docker-compose
I have a Dockerfile to build the container with a Java app:
FROM alpine:latest
ENV ftp_ip 127.0.0.1
ENV mongo_ip 127.0.0.1
ENV quorum_ip http://localhost:22000
RUN apk add --update openjdk8 && mkdir /var/backend/
RUN apk update
COPY license-system-0.0.1-SNAPSHOT.jar /var/backend/
EXPOSE 8080
ENTRYPOINT [ "java", "-jar", "-Dspring.quorum.host=${quorum_ip}", "-Dspring.ftp.server=${ftp_ip}", "-Dspring.data.mongodb.host=${mongo_ip}","/var/backend/license-system-0.0.1-SNAPSHOT.jar" ]
Then, the docker compose file:
version: "3"
services:
backend:
network_mode: host
build: backend
ports:
- "8080:8080"
environment:
- mongo_ip=${mongo_ip}
- ftp_ip=${ftp_ip}
- quorum_ip=${quorum_ip}
Finally, the container is started by a bash command:
quorum_ip="$1" mongo_ip="$2" ftp_ip="$3" docker-compose up -d --build
but docker inspect shows nothing promising. The variables are not set properly (they are using the default values from dockerfile) and the params arent changed even to the default values...
"Env": [
"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
"ftp_ip=127.0.0.1",
"mongo_ip=127.0.0.1",
"quorum_ip=http://localhost:22000"
],
"Cmd": null,
"ArgsEscaped": true,
"Image": "sha256:3ce51f52d70127f22462eafdb60321a4e477a4bec5aa092e860b8485e8575c26",
"Volumes": null,
"WorkingDir": "",
"Entrypoint": [
"java",
"-jar",
"-Dspring.quorum.host=${quorum_ip}",
"-Dspring.ftp.server=${ftp_ip}",
"-Dspring.data.mongodb.host=${mongo_ip}",
"/var/backend/license-system-0.0.1-SNAPSHOT.jar"
]
Am I missing something? Or am I doing something wrong?

Answer 1

If you want to use environmnet varibles in your entrypoint, you should use the "shell form" instead of the "exec form".
ENTRYPOINT java -jar -Dspring.quorum.host=${quorum_ip} -Dspring.ftp.server=${ftp_ip} -Dspring.data.mongodb.host=${mongo_ip} /var/backend/license-system-0.0.1-SNAPSHOT.jar
You could probably make it work with the "exec form" but it only complicates the syntax.

Answer 2

You have to use build args instead of envs to build an image from Dockerfile
Dockerfile
FROM alpine:latest
ARG ftp_ip
ARG mongo_ip
ARG quorum_ip
RUN apk add --update openjdk8 && mkdir /var/backend/
RUN apk update
COPY license-system-0.0.1-SNAPSHOT.jar /var/backend/
EXPOSE 8080
ENTRYPOINT [ "java", "-jar", "-Dspring.quorum.host="${quorum_ip}, "-Dspring.ftp.server="${ftp_ip}, "-Dspring.data.mongodb.host="${mongo_ip},"/var/backend/license-system-0.0.1-SNAPSHOT.jar" ]
docker-compose
version: "3"
services:
backend:
network_mode: host
build:
context: .
dockerfile: ./path/to/backend/Dockerfile
args:
- mongo_ip=${mongo_ip}
- ftp_ip=${ftp_ip}
- quorum_ip=${quorum_ip}
ports:
- "8080:8080"
.env (To pass envs for use in docker-compose. docker-compose automatically fetches envs from .env file if it exists)
ftp_ip=127.0.0.1
mongo_ip=127.0.0.1
quorum_ip=http://localhost:22000
And then run docker-compose build to build image with correct envs