Scala app in docker compose - cannot connect to mysql - mysql

Question

I have seen multiple other questions on similar topics, but none of them provides a solution that solves my problem. I have, to the best of my ability, checked to make sure that I have tried solutions provided in other similar questions, but none of them appear to work (or I am reading them incorrectly).
I have a small Scala-app to ingest data to a MySQL database. Having both the app and the DB locally, everything works fine. When trying to run using docker compose, I can't connect to the database.
Setup:
Docker compose file:
version: '1'
services:
ingester:
restart: always
build:
context: ./data_ingester
dockerfile: Dockerfile
container_name: data_ingester
links:
- database
depends_on:
- database
grafana:
restart: always
image: grafana/grafana
container_name: grafana_display
volumes:
- ./grafana_display/grafana-storage:/var/lib/grafana
ports:
- 3000:3000
links:
- database
depends_on:
- database
database:
restart: always
image: mysql:5.7
container_name: database
ports:
- 3306:3306
volumes:
- ./mysql_db_setup/db_setup.sql:/docker-entrypoint-initdb.d/db_setup.sql
environment:
MYSQL_ROOT_PASSWORD: pwd
MYSQL_DATABASE: db
MYSQL_USER: mysql_user
MYSQL_PASSWORD: mysql_pw
volumes:
ingester:
grafana:
database:
Starting all this using docker-compose, I am then able to use docker exec to get a bash shell in the database-container and add some sample data to a table.
Following that, I go to the web-ui exposed by the grafana-container and set up a MySQL datasource by specifying host:port as "database:3306" (i.e. the name of the database-container as host with the appropriate port).
This works, I can connect to the MySQL db from the grafana-container and visualise the sample data I inserted, so the database seems reachable and all that.
In my Scala program, which is run using sbt in the ingester-container, I am now setting up a connection as follows:
Class.forName("com.mysql.jdbc.Driver")
ConnectionPool.singleton(
"jdbc:mysql://database:3306?characterEncoding=UTF-8",
"mysql_user",
"mysql_pw"
)
Reading all the other similar questions, I figured this is the right way. Given that I can reach the database from the grafana-container when specifying the connection in this way also makes me believe this is how it should be specified. However, when trying to run this, the scala-program dies with the following error:
data_ingester | [info] welcome to sbt 1.6.1 (Oracle Corporation Java 11.0.14)
data_ingester | [info] loading project definition from /DataIngester/project
data_ingester | [info] loading settings for project dataingester from build.sbt ...
data_ingester | [info] set current project to DataIngester (in build file:/DataIngester/)
data_ingester | [info] running Main
data_ingester | 22:57:35.987 [sbt-bg-threads-1] DEBUG scalikejdbc.ConnectionPool$ - Registered connection pool : ConnectionPool(url:jdbc:mysql://database:3306?characterEncoding=UTF-8, user:mysql_user) using factory : <default>
data_ingester | 22:57:35.993 [sbt-bg-threads-1] DEBUG scalikejdbc.ConnectionPool$ - Registered singleton connection pool : ConnectionPool(url:jdbc:mysql://database:3306?characterEncoding=UTF-8, user:mysql_user)
data_ingester | [error] java.net.ConnectException: Connection refused (Connection refused)
data_ingester | [error] at java.base/java.net.PlainSocketImpl.socketConnect(Native Method)
data_ingester | [error] at java.base/java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:412)
data_ingester | [error] at java.base/java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:255)
data_ingester | [error] at java.base/java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:237)
data_ingester | [error] at java.base/java.net.Socket.connect(Socket.java:609)
data_ingester | [error] at java.base/sun.net.NetworkClient.doConnect(NetworkClient.java:177)
data_ingester | [error] at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:474)
data_ingester | [error] at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:569)
data_ingester | [error] at java.base/sun.net.www.http.HttpClient.<init>(HttpClient.java:242)
data_ingester | [error] at java.base/sun.net.www.http.HttpClient.New(HttpClient.java:341)
data_ingester | [error] at java.base/sun.net.www.http.HttpClient.New(HttpClient.java:362)
data_ingester | [error] at java.base/sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1253)
data_ingester | [error] at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1187)
data_ingester | [error] at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1081)
data_ingester | [error] at java.base/sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:1015)
data_ingester | [error] at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1592)
data_ingester | [error] at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1520)
data_ingester | [error] at java.base/java.net.HttpURLConnection.getResponseCode(HttpURLConnection.java:527)
data_ingester | [error] at scalaj.http.HttpRequest.doConnection(Http.scala:367)
data_ingester | [error] at scalaj.http.HttpRequest.exec(Http.scala:343)
data_ingester | [error] at scalaj.http.HttpRequest.asString(Http.scala:492)
data_ingester | [error] at
data_ingester | [error] stack trace is suppressed; run 'last Compile / run' for the full output
data_ingester | [error] (Compile / run) java.net.ConnectException: Connection refused (Connection refused)
data_ingester | [error] Total time: 122 s (02:02), completed Feb 10, 2022, 10:57:36 PM
The most common errors seem to be that you have specified the host incorrectly or not exposed the right ports, but since I can connect to the MySQL-container from the grafana-container I am inclined to believe both the host and ports are set correctly, so I am not sure what I am overlooking.
If you have made it through this far, thank you for reading, and any help is very appreciated!
(FYI: setting up a mysql db on localhost and running the Scala-program locally without docker and just connect to "localhost:3306" works, so it seems the code to actually connect seems to be alright, just that something breaks when running it using docker compose).