Connect external MQTT docker container with springboot docker-compose file - spring

Question

I have a Springboot application with mysql database and now I want to connect to an external MQTT broker.
Following are my configs:
docker-compose.yml
version: '3.5'
networks:
foo:
name: foo
driver: bridge
services:
app-server:
build: .
container_name: Player1
ports:
- "8080:8080"
restart: always
networks:
- foo
depends_on:
- mydb
external_links:
- mosquitto:eclipse-mosquitto
environment:
- SPRING_DATASOURCE_URL=jdbc:mysql://mydb:3306/takeaway_db?serverTimezone=UTC&useLegacyDatetimeCode=false&createDatabaseIfNotExist=true
mydb:
image: mysql
ports:
- "3306:3306"
restart: always
networks:
- foo
environment:
- MYSQL_ROOT_USER=root
- MYSQL_ROOT_PASSWORD=P#ssword1234
volumes:
- /var/lib/mysql
and Dockerfile
FROM adoptopenjdk/openjdk11:alpine-jre
ARG JAR_FILE=target/spring-boot-web.jar
WORKDIR /opt/app
COPY target/*.jar app.jar
ENTRYPOINT ["java","-jar","app.jar"]
application.properties
mqtt.borker.url=tcp://172.18.0.2:1883 #container ip address from container inspect
mqtt.borker.username=username
mqtt.borker.password=password
command for starting MQTT broker
docker run -it -p 1883:1883 --net foo --name mosquitto eclipse-mosquitto
When I run docker-compose up, I get the followig error:
org.eclipse.paho.client.mqttv3.MqttException: Unable to connect to server
................
at java.base/java.lang.Thread.run(Unknown Source) ~[na:na]
Caused by: java.net.ConnectException: Connection refused (Connection refused)
at java.base/java.net.PlainSocketImpl.socketConnect(Native Method) ~[na:na]

Answer 1

Basically the idea behind this solution should apply to connect any docker-compose containers with any other external containers.
Create or add existing containers to a network.
docker network create foo
docker run -it -d -p 1883:1883 --net foo --name mosquitto eclipse-mosquitto
Update docker compose file.
a. Add network foo to the containers.
b. Connect/expose network foo in compose file to the external network foo.
c. Link app container to the external container.
version: '3.5'
services:
app-server:
build: .
container_name: ...
ports:
- "8080:8080"
restart: always
networks:
- foo // =========> (a)
depends_on:
- mydb
external_links:
- mosquitto:eclipse-mosquitto //============> (c)
mydb:
image: mysql
container_name: ...
ports:
- "3306:3306"
restart: always
networks:
- foo // =========> (a)
networks:
foo:
external:
name: foo // ========> (b)
The complete docker file can be found here.
Update links in the application.properties file.
spring.datasource.url=jdbc:mysql://mydb:3306/takeaway_db?createDatabaseIfNotExist=true
mqtt.borker.url=tcp://mosquitto:1883