docker-compose UnknownHostException : but docker run works - docker

Question

I have a docker image (lfs-service:latest) that I'm trying to run as part of a suite of micro services.
RHELS 7.5
Docker version: 1.13.1
docker-compose version 1.23.2
Postgres 11 (installed on RedHat host machine)
The following command works exactly as I would like:
docker run -d \
-p 9000:9000 \
-v "$PWD/lfs-uploads:/lfs-uploads" \
-e "SPRING_PROFILES_ACTIVE=dev" \
-e dbhost=$HOSTNAME \
--name lfs-service \
[corp registry]/lfs-service:latest
This successfully:
creates/starts a container with my Spring Boot Docker image on port
9000
writes the uploads to disk into the lfs-uploads directory
and connects to a local Postgres DB that's running on the host
machine (not in a Docker container).
My service works as expected. Great!
Now, my problem:
I'm tring to run/manage my services using Docker Compose with the following content (I have removed all other services and my api gateway from docker-compose.yaml to simplify the scenario):
version: '3'
services:
lfs-service:
image: [corp registry]/lfs-service:latest
container_name: lfs-service
stop_signal: SIGINT
ports:
- 9000:9000
expose:
- 9000
volumes:
- "./lfs-uploads:/lfs-uploads"
environment:
- SPRING_PROFILES_ACTIVE=dev
- dbhost=$HOSTNAME
Relevant entries in application.yaml:
spring:
profiles: dev
datasource:
url: jdbc:postgresql://${dbhost}:5432/lfsdb
username: [dbusername]
password: [dbpassword]
jpa:
properties:
hibernate:
dialect: org.hibernate.dialect.PostgreSQLDialect
hibernate:
ddl-auto: update
Execution:
docker-compose up
...
The following profiles are active: dev
...
Tomcat initialized with port(s): 9000 (http)
...
lfs-service | Caused by: java.net.UnknownHostException: [host machine hostname]
lfs-service | at
java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:184) ~[na:1.8.0_181]
lfs-service | at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_181]
lfs-service | at java.net.Socket.connect(Socket.java:589) ~[na:1.8.0_181]
lfs-service | at org.postgresql.core.PGStream.<init>(PGStream.java:70) ~[postgresql-42.2.5.jar!/:42.2.5]
lfs-service | at org.postgresql.core.v3.ConnectionFactoryImpl.tryConnect(ConnectionFactoryImpl.java:91) ~[postgresql-42.2.5.jar!/:42.2.5]
lfs-service | at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:192) ~[postgresql-42.2.5.jar!/:42.2.5]
...
lfs-service | 2019-01-11 18:46:54.495 WARN [lfs-service,,,] 1 --- [ main] o.s.b.a.orm.jpa.DatabaseLookup : Unable to determine jdbc url from datasource
lfs-service |
lfs-service | org.springframework.jdbc.support.MetaDataAccessException: Could not get Connection for extracting meta-data; nested exception is org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to obtain JDBC Connection; nested exception is org.postgresql.util.PSQLException: The connection attempt failed.
lfs-service | at org.springframework.jdbc.support.JdbcUtils.extractDatabaseMetaData(JdbcUtils.java:328) ~[spring-jdbc-5.1.2.RELEASE.jar!/:5.1.2.RELEASE]
lfs-service | at org.springframework.jdbc.support.JdbcUtils.extractDatabaseMetaData(JdbcUtils.java:356) ~[spring-jdbc-5.1.2.RELEASE.jar!/:5.1.2.RELEASE]
...
Both methods of starting should be equivalent but obviously there's a functional difference... Any ideas on how to resolve this issue / write a comperable docker-compose file which is functionally identical to the "docker run" command at the top?
NOTE: I've also tried the following values for dbhost: localhost, 127.0.0.1 - this won't work as it attempts to find the DB in the container, and not on the host machine.

Answer 1

CORRECTION:
Unfortunately, while this solution works in the simplest use case - it will break Eureka & API Gateways from functioning, as the container will be running on a separate network. I'm still looking for working solution.
To anyone looking for a solution to this question, this worked for me:
docker-compose.yaml:
lfs-service:
image: [corp repo]/lfs-service:latest
container_name: lfs-service
stop_signal: SIGINT
ports:
- 9000:9000
expose:
- 9000
volumes:
- "./lfs-uploads:/lfs-uploads"
environment:
- SPRING_PROFILES_ACTIVE=dev
- dbhost=localhost
network_mode: host
Summary of changes made to docker-compose.yaml:
change $HOSTNAME to "localhost"
Add "network_mode: host"
I have no idea if this is the "correct" way to resolve this, but since it's only for our remote development server the solution is working for me. I'm open to suggestions if you have a better solution.

Answer 2

Working solution
The simple solution is to just provide the host machine IP address (vs hostname).
environment:
- SPRING_PROFILES_ACTIVE=dev
- dbhost=172.18.0.1
Setting this via an environment variable would probably be more portable:
export DB_HOST_IP=172.18.0.1
docker-compose.yaml
environment:
- SPRING_PROFILES_ACTIVE=dev
- dbhost=${DB_HOST_IP}