Springboot and Mongo containers are not connecting - spring

Question

I'm running 2 containers on my local machine using docker compose. The first one is mongo container and the second is spring boot application.
This is my spring boot's Dockerfile
VOLUME /tmp
ADD target/app.jar app.jar
EXPOSE 8080
RUN bash -c "touch /app.jar"
ENTRYPOINT ["java","-Dspring.data.mongodb.uri=mongodb://mongo/test", "-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]
This is my spring boot's application properties
# mongodb configuration0
dockerspring.data.mongodb.uri= mongodb://mongo:27000/test
This is my docker-compose.yml
version: '3.1'
services:
level-2-springboot:
image: level-2:latest
restart: always
container_name: level_2_microservice
ports:
- 8081:8080
working_dir: /tmp
depends_on:
- mongo
mongo:
image: mongo
container_name: mongo
ports:
- 27000:27017
restart: always
This is my pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.2.6.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.yash</groupId>
<artifactId>spring-sync-ms</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>spring-sync</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
<maven-jar-plugin.version>3.1.1</maven-jar-plugin.version>
</properties>
<dependencies>
<dependency>
<groupId>org.mongodb</groupId>
<artifactId>mongo-java-driver</artifactId>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
<finalName>app</finalName>
</build>
</project>
I execute this to create image for my spring boot app
docker build -t level-2 .
After I see my image, I execute docker-compose up and they work just fine no error
Here is the containers running
But when i do a POST or GET request to localhost:8081/api/employees/ or localhost:8080/api/employees/ I'd get this message from Postman
Could not get any response
Below is my project structure
If I run the app on eclipse and mongo manually and do POST/GET request, I'd get 201 OK, but when I do it using docker in containers, they dont talk to each other. Anyone know whats causing this?

Answer 1

I've consulted the internet and i think i got what you need.
The question that follows is “how does our service container talk to
the Mongo container?” For that, we get into container linking.
When you run a container, you can pass an optional –link parameter,
specifying the running container name that the new container needs to
be able to communicate with.
So with our command
docker run -P -d --name employee --link mongodb microservicedemo/employee
we fire up our new container image, exposing its ports (-P) in the background
(-d), naming it employee (–name), and telling it to link to the
container named “mongodb” (–link). Linking these does the following:
Creates a hosts file entry in the employee container pointing at the
running location of the MongoDB container Inserts a number of
environment variables in the employee container to assist with any
other programmatic access needed.
To see them run: docker exec employee bash -c 'env |grep MONGODB'
Allows containers to communicate directly over ports exposed, so there is no need to
worry about the hose machine part mapping.
see:
https://www.3pillarglobal.com/insights/building-a-microservice-architecture-with-spring-boot-and-docker-part-iii
https://www.3pillarglobal.com/insights/building-a-microservice-architecture-with-spring-boot-and-docker-part-ii

Answer 2

This:
# mongodb configuration0
dockerspring.data.mongodb.uri= mongodb://mongo:27000/test
Should be:
# mongodb configuration0
dockerspring.data.mongodb.uri= mongodb://mongo:27017/test
The two services in your docker-compose.yml expose Ports 8081 and 27000 to the host machine.
But inside the network created by docker-compose they expose Ports 8080 and 27017.
As your Mongo-Container runs in the docker-compose network, it has to use Port 27017 to connect to the database.