Docker-compose - Redis-Springboot

[VidyasagarPandikashala]

#About application

Simple backend applicaction that counts number of visits happened to be done by an user.
Redis stores the data of the visits made.

---

ERROR DESCRIPTION

Springboot application is not able connect to the redis server even though it shows the redis and application are both in same docker network.

It throws error - White label Error (type=Internal Server Error, status=500).

Error in sprinboot-app container:

Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception 
[Request processing failed: 
org.springframework.data.redis.RedisConnectionFailureException: Unable to connect to Redis] with root cause

---

Dockerfile:

FROM openjdk:17
WORKDIR /app
COPY target/visitsapplication-0.0.1-SNAPSHOT.jar app.jar
EXPOSE 8080
CMD ["java", "-jar", "app.jar"]

---

DockerCompose.yml

version: '3'
services:
    redis-server:
    image: 'redis'
    ports:
        - "6379:6379"
    springboot-app:
    build: .
    ports:
        - "8080:8080"  

---

application.properties

server.port=8080
spring.redis.host=redis-server
spring.redis.port=6379

---

VisitController.java

package com.visitapplication.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.ValueOperations;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/")
public class VisitsController {
        @Autowired
        private RedisTemplate<String, String> redisTemplate;

        @GetMapping
        public String getVisits() {
            ValueOperations<String, String> ops = redisTemplate.opsForValue();
            String visits = ops.get("visits");

            if (visits == null) {
                visits = "0";
            }

            ops.set("visits", String.valueOf(Integer.parseInt(visits) + 1));

            return "Number of visits is " + visits;
        }
}

---

Commands run to check the issues

---

Command:

 docker-compose logs springboot-app

Output :

java.net.ConnectException: Connection refused.

---

Command:

docker network inspect visitsapplication_default

Output:

[
    {
        "Name": "visitsapplication_default",
        "Id": "671f39cacd25f8f2c694eebed7515c16dfae3efedc86ae57c567e8ab0567fed2",
        "Created": "2023-12-14T06:06:20.465060571Z",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": null,
            "Config": [
                {
                    "Subnet": "172.20.0.0/16",
                    "Gateway": "172.20.0.1"
                }
            ]
        },
        "Internal": false,
        "Attachable": false,
        "Ingress": false,
        "ConfigFrom": {
            "Network": ""
        },
        "ConfigOnly": false,
        "Containers": {
            "7437823988de4a68b31f72b423d75bd7172be555b7c77879a5f76eb3cb248d1d": {
                "Name": "visitsapplication-redis-server-1",
                "EndpointID": "c138d3fa863efed0accf193acc4992a382245e160840337554fc76f74e3f914e",
                "MacAddress": "02:42:ac:14:00:03",
                "IPv4Address": "172.20.0.3/16",
                "IPv6Address": ""
            },
            "be2ef8d7f9ed05fb7b98e21473948b7f005fa0fb3b268f03105a98ee5ae79eeb": {
                "Name": "visitsapplication-springboot-app-1",
                "EndpointID": "fa1ee3bccb4097dbe8cfb5388eb471c9836e2a84b21e94fc266d3542e0e81e5a",
                "MacAddress": "02:42:ac:14:00:02",
                "IPv4Address": "172.20.0.2/16",
                "IPv6Address": ""
            }
        },
        "Options": {},
        "Labels": {
            "com.docker.compose.network": "default",
            "com.docker.compose.project": "visitsapplication",
            "com.docker.compose.version": "2.17.3"
        }
    }
]

The Docker network inspection confirms that both visitsapplication-redis-server-1 and visitsapplication-springboot-app-1 containers are on the same Docker network named visitsapplication_default. Therefore, they should be able to communicate with each other using their service names (redis-server and springboot-app, respectively).

---

[wilkinsona]

Thanks for the report but it's not clear why you believe that it's a Spring Boot issue. Have you, for example, verified that an application using a Redis client directly is able to connect when the Spring Boot app is not? Unfortunately, we don't have time to perform this problem determination for you. If you can demonstrate that it works without involving Spring Boot but does not work with Spring Boot then we can take another look.

[VidyasagarPandikashala]

The issue is that springboot application is not able to recogonize the redis running in the same container. I need clarification if any settings to be done on application.properties or in the controller class (eg. annotate some dependency related to redis) for the application to connect to the port of the redis application.

Tried running the same syntax and similar docker configuration in nodejs and it is working as expected.
This raised my concern was if it is related to spring boot application and its configuration. If it is not the issue of the spring-boot I truly apologize for taking your precious time.

[wilkinsona]

There's nothing obviously wrong in what you've shared thus far but it's hard to be certain as you haven't provided a complete picture.

Spring Boot knows nothing about Docker's networking. It is the Redis client and the JVM that are responsible for establishing the connection. If they're able to do so without Spring Boot then this may well be a Spring Boot problem but I think it's most likely to be a problem at the level of the JVM or the Redis Client. A Docker problem is also a possibility, although that's less likely if this works with NodeJS.

[VidyasagarPandikashala]

Thank you for the support. @wilkinsona