Agent skill

render-deployment

Guide for deploying Spring Boot backend to Render cloud platform. Use this when deploying, troubleshooting, or managing Render deployments.

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Install this agent skill to your Project

npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/data/render-deployment

SKILL.md

Render Deployment Guide

Deploy Spring Boot applications to Render's free/starter tier.

Render Configuration (render.yaml)

yaml
services:
  - type: web
    name: salon-hub-api
    runtime: docker
    dockerfilePath: ./Dockerfile
    plan: free  # or starter for always-on
    buildCommand: ./gradlew bootJar
    healthCheckPath: /actuator/health
    envVars:
      - key: SPRING_PROFILES_ACTIVE
        value: prod
      - key: DB_PASSWORD
        sync: false  # Set manually in dashboard
      - key: JWT_SECRET
        sync: false

databases:
  - name: salon-hub-db
    databaseName: salon_hub
    user: salon_hub_api
    plan: free

Dockerfile for Render

dockerfile
FROM eclipse-temurin:21-jdk-alpine AS builder
WORKDIR /app
COPY . .
RUN ./gradlew bootJar --no-daemon

FROM eclipse-temurin:21-jre-alpine
WORKDIR /app
COPY --from=builder /app/build/libs/*.jar app.jar

# Render uses PORT env variable
ENV PORT=8082
EXPOSE ${PORT}

ENTRYPOINT ["java", "-XX:+UseContainerSupport", "-XX:MaxRAMPercentage=75.0", "-jar", "app.jar"]

Environment Variables on Render

Set these in Render Dashboard → Environment:

Variable Value
SPRING_PROFILES_ACTIVE prod
DATABASE_JDBC_URL JDBC URL from Render Dashboard
DB_USERNAME Database username from Render
DB_PASSWORD Database password from Render
JWT_SECRET Secure random string (256+ bits)

⚠️ CRITICAL: Getting Database Credentials from Render Dashboard

The MCP API does NOT provide database passwords. You MUST get the actual connection string from the Render Dashboard:

  1. Go to dashboard.render.com
  2. Click on your PostgreSQL database
  3. Click "Connect" button (top-right)
  4. Copy the Internal Database URL or External Database URL

The URL format is:

postgresql://USER:PASSWORD@HOST:PORT/DATABASE

Convert to JDBC format:

jdbc:postgresql://HOST:PORT/DATABASE

Then set environment variables:

  • DATABASE_JDBC_URL: The JDBC URL
  • DB_USERNAME: The username from the URL
  • DB_PASSWORD: The password from the URL (this is what you can't get via API!)

Why MCP Can Connect But Your App Can't

The Render MCP server has internal API access to database credentials that aren't exposed through the public API. When EOFException at doAuthentication occurs:

  1. The password is wrong - Get the actual password from Dashboard
  2. The MCP query_render_postgres tool works because it uses Render's internal credential management
  3. Your app needs the credentials manually set in environment variables

Deploy Methods

1. Auto-Deploy (Recommended)

Connect GitHub repo → Render auto-deploys on push to main

2. Manual Deploy via Dashboard

Render Dashboard → Manual Deploy → Deploy latest commit

3. Deploy Hook (CI/CD)

bash
curl -X POST "https://api.render.com/deploy/srv-YOUR-SERVICE-ID?key=YOUR-DEPLOY-KEY"

4. Render CLI

bash
render deploys create srv-YOUR-SERVICE-ID

Keep Alive for Free Tier

Free tier spins down after 15 min of inactivity. Use GitHub Actions:

yaml
# .github/workflows/keep-alive.yml
name: Keep Render Alive

on:
  schedule:
    - cron: '*/5 * * * *'  # Every 5 minutes

jobs:
  ping:
    runs-on: ubuntu-latest
    steps:
      - name: Ping Health Endpoint
        run: |
          curl -s https://YOUR-APP.onrender.com/actuator/health

Health Check Configuration

Render pings your health endpoint to verify deployment success:

yaml
# application-prod.yml
management:
  endpoints:
    web:
      exposure:
        include: health,info
  endpoint:
    health:
      show-details: never  # Don't expose internals

Troubleshooting

Deploy Fails - Check Logs

  1. Render Dashboard → Logs
  2. Look for startup errors
  3. Common issues: missing env vars, DB connection, port binding

App Not Starting

  • Ensure PORT environment variable is used (Render sets this)
  • Check memory limits (free tier: 512MB)
  • Verify health endpoint responds within timeout

Database Connection Issues - CRITICAL

IMPORTANT: PostgreSQL connection requires specific URL formats!

Internal vs External URLs

Render provides TWO database URLs:

Type Format Use Case
Internal dpg-xxx-a:5432 Services in same Render region (faster, no SSL)
External dpg-xxx-a.oregon-postgres.render.com:5432 External access (requires SSL)

⚠️ PORT IS REQUIRED!

The port :5432 is ALWAYS required, even for internal URLs:

yaml
# ❌ WRONG - Missing port causes EOFException
spring:
  datasource:
    url: jdbc:postgresql://dpg-xxx-a/salon_hub_db

# ✅ CORRECT - Always include :5432
spring:
  datasource:
    url: jdbc:postgresql://dpg-xxx-a:5432/salon_hub_db

Internal URL Configuration (Recommended for Render-to-Render)

yaml
# prod.yml - For services within Render's network
spring:
  datasource:
    url: ${DATABASE_JDBC_URL:jdbc:postgresql://dpg-xxx-a:5432/database_name}
    username: ${DB_USERNAME:db_user}
    password: ${DB_PASSWORD:password}
    driver-class-name: org.postgresql.Driver

Environment variables on Render:

DATABASE_JDBC_URL=jdbc:postgresql://dpg-xxx-a:5432/database_name
DB_HOST=dpg-xxx-a
DB_PORT=5432
DB_NAME=database_name
DB_USERNAME=db_user
DB_PASSWORD=password

External URL Configuration (For external access)

yaml
# Requires SSL for external connections
spring:
  datasource:
    url: jdbc:postgresql://dpg-xxx-a.oregon-postgres.render.com:5432/database_name?sslmode=require

Common Database Errors and Solutions

Error Cause Solution
EOFException: null at doAuthentication Missing port :5432 Add :5432 to URL
The connection attempt failed Wrong hostname or network issue Use internal URL for Render services
SSL required External URL without SSL Add ?sslmode=require to external URLs
Connection refused Wrong host or DB not running Verify DB status in Render dashboard

Environment Variables Required for Database

Variable Example Value Notes
DATABASE_URL postgresql://user:pass@host:5432/db Standard format
DATABASE_JDBC_URL jdbc:postgresql://host:5432/db For Spring Boot
DB_HOST dpg-xxx-a Internal hostname
DB_PORT 5432 Always 5432 for PostgreSQL
DB_NAME salon_hub_db Database name
DB_USERNAME salon_hub_db_user Database user
DB_PASSWORD secret Database password

Cold Start Slow

Free tier takes 30-60 seconds to spin up. Options:

  • Use keep-alive cron job
  • Upgrade to starter plan ($7/month)

Production Configuration Best Practices

yaml
# prod.yml
spring:
  jpa:
    hibernate:
      ddl-auto: update    # NEVER use create-drop in production!
    show-sql: false       # Disable SQL logging for performance
  flyway:
    enabled: true         # Use migrations for schema changes
    baseline-on-migrate: true

WARNING: ddl-auto: create-drop will DELETE ALL DATA on every restart!

Using Render MCP Tools

You can manage Render from VS Code using the Render MCP server:

Setup

Add to .vscode/mcp.json:

json
{
  "servers": {
    "render": {
      "url": "https://mcp.render.com/mcp",
      "headers": {
        "Authorization": "Bearer YOUR_RENDER_API_KEY"
      }
    }
  }
}

Available MCP Tools

Tool Description
mcp_render_list_services List all services in workspace
mcp_render_list_deploys View deployment history
mcp_render_list_logs Get application logs
mcp_render_list_postgres_instances List databases
mcp_render_update_environment_variables Update env vars (triggers deploy)
mcp_render_get_metrics CPU/memory/bandwidth metrics

Common MCP Operations

# Check deployment status
Ask: "List recent deploys for salon-hub-api"

# View error logs
Ask: "Show error logs for srv-xxx service"

# Update environment variables
Ask: "Update DATABASE_JDBC_URL to jdbc:postgresql://host:5432/db"

URLs

Resource URL
API Base https://salon-hub-api.onrender.com
Health https://salon-hub-api.onrender.com/actuator/health
Swagger https://salon-hub-api.onrender.com/swagger-ui.html
Dashboard https://dashboard.render.com

Deployment Checklist

  • All tests pass locally: ./gradlew check
  • Dockerfile builds successfully
  • Environment variables set in Render
  • Database provisioned and connected
  • Push to main branch
  • Verify deployment in Render dashboard
  • Test health endpoint responds
  • Test critical API endpoints

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