Claude Code integration

Docker Compose Services Fail to Connect Due to Wrong Names

Your Docker Compose setup generated by Claude Code has services that fail to connect to each other. The application container can't reach the database, the backend can't connect to Redis, or the worker can't find the message broker. Everything works when running services individually but fails in Docker Compose.

Docker Compose creates a network where services can reach each other by their service name. When the application code uses 'localhost' or hardcoded IPs instead of service names, or when service names in docker-compose.yml don't match what the application expects, connections fail.

This is especially frustrating because the error messages often just say 'connection refused' or 'host not found' without indicating that the issue is a name mismatch.

Error Messages You Might See

Error: connect ECONNREFUSED 127.0.0.1:5432 psql: could not connect to server: Connection refused redis.exceptions.ConnectionError: Error connecting to redis:6379 getaddrinfo ENOTFOUND database Name or service not known
Error: connect ECONNREFUSED 127.0.0.1:5432psql: could not connect to server: Connection refusedredis.exceptions.ConnectionError: Error connecting to redis:6379getaddrinfo ENOTFOUND databaseName or service not known

Common Causes

  • Using localhost instead of service name — Application code connects to localhost:5432 but the database is in a separate container reachable by its service name
  • Service name mismatch — docker-compose.yml defines the service as 'postgres' but the app config references 'db' or 'database'
  • Missing depends_on — The app container starts before the database is ready to accept connections
  • Wrong port mapping confusion — Using the host-mapped port (5433) instead of the container's internal port (5432)
  • Custom network not shared — Services in different docker-compose files or custom networks can't see each other

How to Fix It

  1. Replace localhost with service names — Change database URLs from localhost:5432 to postgres:5432 (matching the service name in docker-compose.yml)
  2. Use environment variables for hostnames — Define DB_HOST, REDIS_HOST as environment variables in docker-compose.yml pointing to the correct service names
  3. Add proper health checks — Use healthcheck in docker-compose.yml and depends_on with condition: service_healthy to wait for dependencies
  4. Use internal container ports — Between containers, always use the internal port (5432), not the host-mapped port (5433:5432)
  5. Verify with docker compose exec — Shell into a container and try to ping or connect to the service name to debug networking

Real developers can help you.

Stanislav Prigodich Stanislav Prigodich 15+ years building iOS and web apps at startups and enterprise companies. I want to use that experience to help builders ship real products - when something breaks, I'm here to fix it. Basel Issmail Basel Issmail ’m a Senior Full-Stack Developer and Tech Lead with experience designing and building scalable web platforms. I work across the full development lifecycle, from translating business requirements into technical architecture to delivering reliable production systems. My work focuses on modern web technologies, including TypeScript, Angular, Node.js, and cloud-based architectures. I enjoy solving complex technical problems and helping teams turn product ideas and prototypes into working platforms that can grow and scale. In addition to development, I often collaborate closely with product managers, business analysts, designers, and QA teams to ensure that solutions align with both technical and business goals. I enjoy working with startups and product teams where I can contribute both as a hands-on engineer and as a technical partner in designing and delivering impactful software. Tejas Chokhawala Tejas Chokhawala Full-stack engineer with 5 years experience building production web apps using React, Next.js and TypeScript. Focused on performance, clean architecture and shipping fast. Experienced with Supabase/Postgres backends, Stripe billing, and building AI-assisted developer tools. Matthew Butler Matthew Butler Systems Development Engineer @ Amazon Web Services prajwalfullstack prajwalfullstack Hi Im a full stack developer, a vibe coded MVP to Market ready product, I'm here to help Caio Rodrigues Caio Rodrigues I'm a full-stack developer focused on building practical and scalable web applications. My main experience is with **React, TypeScript, and modern frontend architectures**, where I prioritize clean code, component reusability, and maintainable project structures. I have strong experience working with **dynamic forms, state management (Redux / React Hook Form), and complex data-driven interfaces**. I enjoy solving real-world problems by turning ideas into reliable software that companies can actually use in their daily operations. Beyond coding, I care about **software quality and architecture**, following best practices for componentization, code organization, and performance optimization. I'm also comfortable working across the stack when needed, integrating APIs, handling business logic, and helping transform prototypes into production-ready systems. My goal is always to deliver solutions that are **simple, efficient, and genuinely useful for the people using them.** Vlad Temian Vlad Temian 15+ years shipping production infrastructure for startups. Former CTO at qed.builders (acquired by The Sandbox). Cursor ambassador and agentic tooling builder. I've scaled systems, automated deployments, and built observability tools for AI coding workflows. I specialize in taking vibe-coded apps from broken prototype to production-ready: fixing Supabase auth/RLS, Stripe integrations, deployment pipelines, and cleaning up AI-generated spaghetti. I build tools in this space (agentprobe, claudebin, micode) and understand both sides: how AI generates code and why it breaks. https://blog.vtemian.com/ Taufan Taufan I’m a product-focused engineer and tech leader who builds scalable systems and turns ideas into production-ready platforms. Over the past years, I’ve worked across startups and fast-moving teams, leading backend architecture, improving system reliability, and shipping products used by thousands of users. My strength is not just writing code — but connecting product vision, technical execution, and business impact. David Olverson David Olverson Solo dev shipping production apps with AI-assisted development. I specialize in rescuing broken Lovable/Bolt/Cursor builds and taking them to production. 10+ apps shipped including SaaS CRMs, gaming platforms, real estate tools, and Discord bots. Stack: Next.js 16, TypeScript, Tailwind CSS, FastAPI, PostgreSQL, Prisma. I use Claude Code with 50+ custom skills for rapid delivery. Average turnaround: 2-4 weeks from broken prototype to production. Jacek Rozanski Jacek Rozanski Senior PHP/Symfony developer and DevOps engineer with 20+ years of professional experience, running opcode.pl (web development agency, est. 2004). Day job: I'm the sole backend developer at merketing company where I own and maintain 11 PHP/Symfony microservices on AWS (ECS Fargate, RDS, S3, CloudFront), handle the full CI/CD pipeline (Bitbucket Pipelines, Docker), and manage monitoring with Sentry and CloudWatch. These services handle high request volumes in production every month. What I bring to AI-built apps: - I audit and fix security issues (OWASP methodology), performance bottlenecks, and architectural problems in codebases generated by Cursor, Claude Code, Lovable, Bolt, and v0 - I refactor AI-generated prototypes into production-grade applications with proper error handling, testing, and clean architecture (SOLID, DDD, hexagonal architecture) - I set up the infrastructure AI tools don't touch: AWS hosting, CI/CD pipelines, automated deployments, database optimization, monitoring, and alerting - I integrate external services: payment providers, email systems, partner APIs, SSO/auth Tech stack: PHP 8.x, Symfony, React, Next.js, PostgreSQL, MySQL, Docker, AWS (ECS, RDS, S3, SQS/SNS, CloudFront), Terraform, Supabase. I also use AI tools daily (Claude Code, Cursor) in my own workflow, so I understand both the strengths and the gaps in AI-generated code. Based in Poland (CET timezone). Available for async work and calls during EU/US business hours.

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Frequently Asked Questions

Why can't my app container connect to the database using localhost?

In Docker Compose, each service runs in its own container with its own network namespace. localhost refers to the container itself, not other containers. Use the service name defined in docker-compose.yml (e.g., 'postgres') as the hostname.

How do I wait for the database to be ready before starting my app?

Use depends_on with a health check. Define a healthcheck on the database service (e.g., pg_isready) and set depends_on: postgres: condition: service_healthy on your app service.

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