Docker Tomcat container unable to access Postgres container - postgresql

Question

I have a alpine docker with postgres, with listen address '*' and listening to 5432, which I'm deploying using
docker run -d --name postgres me/postgres:v1
and my tomcat container with oracle jre8, on which I'm deploying my rest web service using:
# Set environment
ENV CATALINA_HOME /opt/tomcat
EXPOSE 8080
# Launch Tomcat on startup
CMD ${CATALINA_HOME}/bin/catalina.sh run
RUN rm -rf ${CATALINA_HOME}/webapps/docs \
${CATALINA_HOME}/webapps/examples \
${CATALINA_HOME}/webapps/ROOT
# Deploying war file
ADD myapp.war ${CATALINA_HOME}/webapps/ROOT.war
# Restarting server after deploying
CMD ${CATALINA_HOME}/bin/catalina.sh run
And deploying it with
docker run -d -p 8080:8080 --name tomcat --link postgres:postgres me/tomcat:v1
Both are being executed on my laptop, with IP address 192.168.x.x, and I checked the port is listening.
Unfortunately my web service on tomcat cannot connect to the postgres service using
jdbc:postgresql://192.168.x.x:5432/dBName
Alternate I already tried: I launched postgres on it's own port using,
docker run -d -p 5432:5432 --name postgres me/postgres:v1
docker run -d -p 8080:8080 --name tomcat me/tomcat:v1
Then used
jdbc:postgresql://192.168.x.x:5432/dBName
and
jdbc:postgresql://localhost:5432/dBName
but neither seems to work.
In both cases I can see my web server running in tomcat manager, and I am able to access my dB using
psql -h localhost -p 5432 -d dBName -U myUser
as well as pgAdmin.
Any help in resolving this is appreciated.
Solution Update: While using --link, point to postgres (i.e., your postgresql container name) instead of IP
jdbc:postgresql://postgres:5432/dBName
Many thanks to #larsks for pointing it out.

Answer 1

While using --link, point to postgres (i.e., your postgresql container name) instead of IP
jdbc:postgresql://postgres:5432/dBName
So for a full solution, run your postgresql and tomcat container
docker run -d --name postgres me/postgresql:v1
docker run -d -p 8080:8080 --name tomcat --link postgres:postgres me/tomcat:v1
(Notice here I didn't put port for postgres container since it will already have 5432 exposed internally, unless you want to hit it from outside your host, you don't need to specify a port here)
And your server war file will the jdbc address above, postgres will automatically resolve to the container's IP address when they are linked.
Many thanks to #larsks for pointing it out.