Containerizing Spring Boot: Debugging Docker Database Connection Issues in Finovara

Deploying Finovara on Docker and fixing a critical bug.

Marcin Parśniak migrated the Finovara Spring Boot application to a containerized Docker environment. The transition revealed a silent failure where the application connected to an incorrect database instance despite valid configuration files.

Why This Matters

In ideal models, containerization provides isolated environments that prevent external interference. However, technical reality often involves local port collisions—such as the default 5432 port—which can cause applications to bind to existing host services rather than the intended containerized instances, leading to data inconsistency and invisible code changes during development cycles.

Key Insights

• PostgreSQL 15 provides a pg_isready utility used within Docker healthchecks to ensure service availability before application startup (2026).
• Container-to-Host port mapping (5432:5432) can lead to silent shadowing if a local database service is already running on the host machine.
• Eclipse Temurin 21-JDK serves as the base image for Java 21 applications, providing a stable runtime for personal finance management platforms like Finovara.

Working Examples

Docker Compose configuration for the PostgreSQL database service with healthchecks.

services:
  finovara-db:
    image: postgres:15
    container_name: finovara-db
    restart: always
    environment:
      POSTGRES_DB: finovara
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: ${DB_PASSWORD}
    ports:
      - "5432:5432"
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 5s
      retries: 10

Dockerfile for the Finovara Spring Boot backend using JDK 21.

FROM eclipse-temurin:21-jdk
WORKDIR /app
COPY target/*.jar app.jar
ENTRYPOINT ["java", "-jar", "app.jar"]

Practical Applications

• Use case: Finovara finance platform uses healthchecks to verify PostgreSQL readiness before processing income and expense operations. Pitfall: Using default ports (5432) without checking host availability can result in connecting to a legacy database service.
• Use case: Environment variable management via .env files for DB_PASSWORD in Spring Boot deployments. Pitfall: Reusing identical credentials across test and development environments makes it difficult to detect when the application connects to the wrong instance.

References:

• https://dev.to/m4rc1nek/deploying-finovara-on-docker-and-fixing-a-critical-bug-2k5n