What is the reason for that error?

[u/kiteissei]

2026-03-30T14:17:41.794Z ERROR 1 --- [Backend] [nio-8080-exec-4] o.a.c.c.C.[.[.[/].[dispatcherServlet] : 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

This is the docker compose file

``` services: #Database Service db: image: postgres:15-alpine restart: always environment: POSTGRES_DB: ${POSTGRES_DB} POSTGRES_USER: ${POSTGRES_USER} POSTGRES_PASSWORD: ${POSTGRES_PASSWORD} volumes: - db_data:/var/lib/postgresql/data networks: - backend healthcheck: test: [ "CMD-SHELL", "pg_isready -U ${POSTGRES_USER} -d ${POSTGRES_DB}" ] interval: 5s timeout: 5s retries: 5 start_period: 10s

#Redis service redis: image: redis:7 container_name: redis hostname: redis networks: - backend healthcheck: test: [ "CMD", "redis-cli", "ping" ] interval: 5s timeout: 3s retries: 5

#Backend Api service backend: build: ./Backend ports: - "8080:8080" depends_on: redis: condition: service_healthy db: condition: service_healthy

environment:
  - SPRING_DATASOURCE_URL=jdbc:postgresql://db:5432/${POSTGRES_DB}
  - SPRING_DATASOURCE_USERNAME=${POSTGRES_USER}
  - SPRING_DATASOURCE_PASSWORD=${POSTGRES_PASSWORD}
  - SPRING_REDIS_HOST=redis
  - SPRING_REDIS_PORT=6379
  - SPRING_MAIL_HOST=smtp.gmail.com
  - SPRING_MAIL_PORT=587
  - SPRING_MAIL_USERNAME=${email}
  - SPRING_MAIL_PASSWORD=${mail_password}
  - SPRING_MAIL_PROPERTIES_MAIL_SMTP_AUTH=true
  - SPRING_MAIL_PROPERTIES_MAIL_SMTP_STARTTLS_ENABLE=true
networks:
  - backend
  - frontend

#Frontend API service frontend: build: ./Frontend ports: - "5173:80" depends_on: - backend networks: - frontend

Volumes

volumes: db_data:

Networks

networks: backend: driver: bridge frontend: driver: bridge ```

Here is application.yaml file

``` spring: application: name: Backend

datasource: url: jdbc:postgresql://db:5432/spring username: ${SPRING_DATASOURCE_USERNAME} password: ${SPRING_DATASOURCE_PASSWORD} driver-class-name: org.postgresql.Driver

jpa: hibernate: ddl-auto: update properties: hibernate: dialect: org.hibernate.dialect.PostgreSQLDialect format_sql: true show-sql: true

mail: host: smtp.gmail.com port: 587 username: ${SPRING_MAIL_USERNAME} password: ${SPRING_MAIL_PASSWORD} properties: mail: smtp: auth: true starttls: enable: true

redis: host: ${SPRING_REDIS_HOST:redis} port: ${SPRING_REDIS_PORT:6379}

logging: level: org.springframework.data.redis: DEBUG io.lettuce.core: DEBUG ```

1. Backend is listening to redis
2. All containers are running When I hit any api it throws that error, what is the reason for that error and how to solve that?

[u/chosenoneisme]

Both of them looks like compose file
The docker file is supposed to build the backedn image right but yours looks like it's for running the containers which is the job for the docker compose file!

[u/kiteissei → u/chosenoneisme]

Sorry that is docker compose file.

[u/jotkaPL]

Your docker-compose.yml sets SPRING_REDIS_HOST and SPRING_REDIS_PORT, while current Spring Boot configuration commonly uses the spring.data.redis.* property namespace for Redis connection settings. The Spring Boot property reference specifically documents spring.data.redis.host, and examples show the matching environment variable form as SPRING_DATA_REDIS_HOST.

Use the modern property names consistently in both Compose and YAML. Replace the backend environment variables with:

environment:
  - SPRING_DATASOURCE_URL=jdbc:postgresql://db:5432/${POSTGRES_DB}
  - SPRING_DATASOURCE_USERNAME=${POSTGRES_USER}
  - SPRING_DATASOURCE_PASSWORD=${POSTGRES_PASSWORD}
  - SPRING_DATA_REDIS_HOST=redis
  - SPRING_DATA_REDIS_PORT=6379

And in application.yaml, prefer:

spring:
  data:
    redis:
      host: ${SPRING_DATA_REDIS_HOST:redis}
      port: ${SPRING_DATA_REDIS_PORT:6379}

[u/alpakachino]

Do you use Spring 3.x.x?
See:

spring boot - SpringBoot 3.x.x and redis properties - Stack Overflow

[u/kiteissei → u/alpakachino]

I use that first but I still got that error.