Spring Boot database connection does not work when in Docker

Question

I have a SpringBoot application, that runs perfectly on Tomcat and connects to a Postgres database.

e.g. application.properties

# approval datasource
spring.datasource2.driver-class-name=org.postgresql.Driver
spring.datasource2.jdbc-url=jdbc:postgresql://localhost:5432/approval
spring.datasource2.username=postgres
spring.datasource2.password=

Next I have Dockerised the application:

Dockerfile

FROM openjdk:14
ARG JAR_FILE=target/*.jar
COPY ${JAR_FILE} nexct-approval-service.jar
EXPOSE 8081
ENTRYPOINT ["java","-jar","/nexct-approval-service.jar"]

I can access a restful service in the application, however it is giving the following error:

org.postgresql.util.PSQLException: Connection to localhost:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.

Everything is running on localhost and I plan to deploy this to a linux server where everying runs on the same host too.

Question

Why does docker seem to change the host access? How do I configure this so that it can access the database using docker?

Hi Muhammad, nope I am not. Should I be? I don't have much docker experience — Richard, Jul 20 '20 at 12:34
Ok adding docker-compose in answer, which works fine for me. — Muhammad Waqas Dilawar, Jul 20 '20 at 12:34
Thanks for pointing me in the right direction. I will read up on how docker-compose works. — Richard, Jul 20 '20 at 12:35
I might be wrong, but it looks like `docker-compose.yml` will create a new postrgres database. I need to connect to an existing database that is used by multiple applications. — Richard, Jul 20 '20 at 12:43
So you have problem in connecting app running in Docker container with Postgres installed in system and running? — Muhammad Waqas Dilawar, Jul 20 '20 at 12:46
Yes, but I have just seen your answer. I am giving it a try. I looks like it will work with an existing database. — Richard, Jul 20 '20 at 12:49
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/218210/discussion-between-muhammad-waqas-dilawar-and-richard). — Muhammad Waqas Dilawar, Jul 20 '20 at 13:01

Muhammad Waqas Dilawar · Accepted Answer · 2020-07-20T17:47:06.643

3

Solution for Mac: Inside your docker container simply have the db host set to host.docker.internal. This will be forwarded to the host the docker container is running on. Reference

Solution for Linux: Actually what you really need to do is connect your container with Postgres running on host system, so for that we need to tell Docker to set network mode to host.

  docker run -it --network=host -p 8081:8081 --name containerName 'imageName'

Or using docker-compose.yml:

To start the containers just issue following command docker-compose up

version: '3.7'

services:

  configurator:
    container_name: 'nameOfContainer'
    image: 'imageName'
    network_mode: "host"
    ports:
      - "8081:8081"
    restart: on-failure

For further learning please follow the docs.

edited Jul 20 '20 at 17:47

answered Jul 20 '20 at 12:43

Muhammad Waqas Dilawar

1,844
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What should the `nameOfContainer` and `imageName` be? Surly if I build the docker image on a new server, this will be different? – Richard Jul 20 '20 at 12:52
1

**nameOfContainer** can be anything and you can tag image while building for name consistency. **docker build -t imageName:tagName .** – Muhammad Waqas Dilawar Jul 20 '20 at 12:57
If I change the entry in `application.properties` to `spring.datasource2.jdbc-url=jdbc:postgresql://my-postgres:5432/approval`, I get the following error: `HikariPool-1 - jdbcUrl is required with driverClassName.` – Richard Jul 20 '20 at 13:00
1

Kindly join me in chat. – Muhammad Waqas Dilawar Jul 20 '20 at 13:01
I think we need more entries here to chat? – Richard Jul 20 '20 at 13:03
Are you still here? – Richard Jul 20 '20 at 13:07
Check in question comments. – Muhammad Waqas Dilawar Jul 20 '20 at 13:07
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/218211/discussion-between-richard-and-muhammad-waqas-dilawar). – Richard Jul 20 '20 at 13:07
1

@Richard updated the answer. This is how it works now. I've tested in Ubuntu. – Muhammad Waqas Dilawar Jul 20 '20 at 17:39
I am inexperienced with docker-compose. I tried your answer above, but on `docker-compose up`, I get: `Pulling configurator (nexct-approval-service-image:)... ERROR: The image for the service you're trying to recreate has been removed. If you continue, volume data could be lost. Consider backing up your data before continuing. Continue with the new image? [yN]y Pulling configurator (nexct-approval-service-image:)... ERROR: pull access denied for nexct-approval-service-image, repository does not exist or may require 'docker login': denied: requested access to the resource is denied` – Richard Jul 21 '20 at 06:31
DId you try command `docker run -it --network=host -p 8081:8081 --name containerName 'imageName'` – Muhammad Waqas Dilawar Jul 21 '20 at 06:33
No, I didn't, will try thanks. I thought the yml file would build it. But I a was wrong. – Richard Jul 21 '20 at 06:37
Check the chat window, I've posted some comments there. – Muhammad Waqas Dilawar Jul 21 '20 at 06:38
So is it better to use the `Dockerfile` only and not use `docker-compose up`? – Richard Jul 21 '20 at 06:41
Dockerfile is used to build image and docker-compose is used to build that image based on Dockerfile and then run it. – Muhammad Waqas Dilawar Jul 21 '20 at 06:43
I'm confused. Do I need to do `docker run -it --network=host -p 8081:8081 --name containerName 'imageName'` AND or OR the `docker-compose.yml` file config above? – Richard Jul 21 '20 at 06:53
This is command `docker run -it --network=host -p 8081:8081 --name containerName 'imageName'` – Muhammad Waqas Dilawar Jul 21 '20 at 06:58
So then do I need `docker-compose.yml`? – Richard Jul 21 '20 at 07:02
Do I run `docker build` before? – Richard Jul 21 '20 at 07:03
Extended discussion should be in chat. – Muhammad Waqas Dilawar Jul 21 '20 at 07:04

Spring Boot database connection does not work when in Docker

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