replacing args in docker file is not working - docker

Question

I have the following docker file
FROM alpine:3.10 as builder
# CAMUNDA VARIABLES
ARG VERSION=7.12.0
ARG DISTRO=tomcat
ARG SNAPSHOT=false
ARG EE=true
#Understand difference between ARG and ENV:
#https://vsupalov.com/docker-arg-vs-env/
#AZURE SQL VARIABLES, DEFAULT SETTINS ARE DEV DB Environment
#Be sure database and tables are created upfront
#Use docker build . -t xx/camundawithbasicdev
#Use docker build . -t xx/camundawithbasicauthqa --build-arg SQLSERVER=a_value DBPASSWORD=a_value DBUSERNAME=a_value
#Use docker build . -t xx/camundawithbasicauthprod --build-arg some_variable_name=a_value
#And replace variables as needed.
ARG SQLSERVER=xx
ARG DBPASSWORD=Hxx
ARG DBUSERNAME=xx
ARG DATABASENAME=xx
RUN apk add --no-cache \
ca-certificates \
maven \
tar \
wget \
xmlstarlet
COPY settings.xml download.sh camunda-tomcat.sh camunda-wildfly.sh /tmp/
RUN /tmp/download.sh
#Enable Basic AUTH
COPY web.xml /camunda/webapps/engine-rest/WEB-INF/web.xml
##### FINAL IMAGE #####
FROM alpine:3.10
ARG VERSION=7.12.0
ENV CAMUNDA_VERSION=${VERSION}
ENV DB_DRIVER=com.microsoft.sqlserver.jdbc.SQLServerDriver
ENV DB_URL=jdbc:sqlserver://${SQLSERVER}.database.windows.net:1433;database=${DATABASENAME};user=${DBUSERNAME};password={DBPASSWORD};encrypt=true;trustServerCertificate=false;hostNameInCertificate=*.database.windows.net;loginTimeout=30;
ENV DB_USERNAME=${DBUSERNAME}
ENV DB_PASSWORD=${DBPASSWORD}
ENV DB_CONN_MAXACTIVE=20
ENV DB_CONN_MINIDLE=5
ENV DB_CONN_MAXIDLE=20
ENV DB_VALIDATE_ON_BORROW=true
ENV DB_VALIDATION_QUERY="SELECT 1"
ENV SKIP_DB_CONFIG=
ENV WAIT_FOR=
ENV WAIT_FOR_TIMEOUT=120
ENV TZ=UTC
ENV DEBUG=TRUE
ENV JAVA_OPTS="-Xmx768m -XX:MaxMetaspaceSize=256m"
ENV JMX_PROMETHEUS=false
EXPOSE 8080 8000
# Downgrading wait-for-it is necessary until this PR is merged
# https://github.com/vishnubob/wait-for-it/pull/68
RUN apk add --no-cache \
bash \
ca-certificates \
openjdk11-jre-headless \
tzdata \
tini \
xmlstarlet \
&& wget -O /usr/local/bin/wait-for-it.sh \
"https://raw.githubusercontent.com/vishnubob/wait-for-it/a454892f3c2ebbc22bd15e446415b8fcb7c1cfa4/wait-for-it.sh" --no-check-certificate \
&& chmod +x /usr/local/bin/wait-for-it.sh
RUN addgroup -g 1000 -S camunda && \
adduser -u 1000 -S camunda -G camunda -h /camunda -s /bin/bash -D camunda
# end ssh config
WORKDIR /camunda
USER camunda
#MSSQL SERVER JDBC DRIVER INSTALL
COPY mssql-jdbc-7.2.2.jre11.jar /camunda/lib/
ENTRYPOINT ["/sbin/tini", "--"]
CMD "./camunda.sh"
COPY --chown=camunda:camunda --from=builder /camunda .
However when I run the image, it looks like the variables are not replaced on the connection string part
what am I missing?

Answer 1

You're setting the arguments on a different stage. As far as I know, it's not possible to pass them between stages. For example:
This won't work
FROM alpine:3.10 as builder
ARG TEST1=1234
FROM alpine:3.10
ENV TEST2=blablah-${TEST1}
if you print TEST2 you'll get blablah-
This will:
FROM alpine:3.10 as builder
ARG TEST1=1234
FROM alpine:3.10
ARG TEST1=98765
ENV TEST2=blablah-${TEST1}
if you print TEST2 you'll get `blahblah-98765
However, I would strongly advice against this way as it'll store your passwords and so on as default env vars in the Docker image you're building. I would pass the connection details when you run docker either with docker run -e TEST1=1234 or even better, with a docker-compose file.
I would have Dockerfile like this one (very simplified, only with the env vars) Normally, when I need to construct variables like that I do so in the entrypoint.sh
So my entrypoint looks like:
#!/bin/bash
export DB_URL="jdbc:sqlserver://${SQLSERVER}.database.windows.net:1433;database=${DB_NAME};user=${DB_USERNAME};password=${DB_PASSWORD};encrypt=true;trustServerCertificate=false;hostNameInCertificate=*.database.windows.net;loginTimeout=0;"
echo $DB_URL
echo "Running: '$#'"
exec $#
My Dockerfile looks like:
FROM alpine:3.10 as builder
ARG VERSION
ARG DISTRO
ARG SNAPSHOT
ARG EE
FROM alpine:3.10
ARG VERSION
ENV CAMUNDA_VERSION=${VERSION}
ENV DB_DRIVER=com.microsoft.sqlserver.jdbc.SQLServerDriver
ENV DB_CONN_MAXACTIVE=20
ENV DB_CONN_MINIDLE=5
ENV DB_CONN_MAXIDLE=20
ENV DB_VALIDATE_ON_BORROW=true
ENV DB_VALIDATION_QUERY="SELECT 1"
ENV SKIP_DB_CONFIG=
ENV WAIT_FOR=
ENV WAIT_FOR_TIMEOUT=120
ENV TZ=UTC
ENV DEBUG=TRUE
ENV JAVA_OPTS="-Xmx768m -XX:MaxMetaspaceSize=256m"
ENV JMX_PROMETHEUS=false
RUN apk update && apk add bash
ADD entrypoint.sh /
ENTRYPOINT ["/entrypoint.sh"]
And my docker-compose.yml
version: '2.3'
services:
so-example:
image: stackoverflow-example
build:
context: .
args:
- VERSION
- DISTRO
- SNAPSHOT
environment:
- SQLSERVER
- DB_USERNAME
- DB_PASSWORD
- DB_NAME
Then, to build the new image I run:
docker-compose build --build-arg VERSION=7.12.0 --build-arg DISTRO=tomcat --build-arg SNAPSHOT=false --build-arg EE=true
When I need to run it I export the values I need. For instance:
export SQLSERVER=myhost
export DB_USERNAME=db_user
export DB_PASSWORD=mysecretpassword
export DB_NAME=mydb
And then run it with compose. For example, if I run
docker-compose run so-example env
you should see that DB_URL is
jdbc:sqlserver://myhost.database.windows.net:1433;database=mydb;user=db_user;password=mysecretpassword;encrypt=true;trustServerCertificate=false;hostNameInCertificate=*.database.windows.net;loginTimeout=0;
I hope this helps