**Tags:** "Hello World" Examples · Python # Python Hello World A [Python](https://python.org) 3.11 application built with Flask and served by Gunicorn, backed by [PostgreSQL](https://zerops.io) on [Zerops](https://zerops.io). Demonstrates vendored dependencies via `pip --target`, idempotent database migrations, and a production-ready WSGI setup — paired with six ready-made environment configurations from AI agent workspaces to highly-available production. ### Available Environments - [AI Agent](https://app.zerops.io/recipes/python-hello-world.md?environment=ai-agent) - [Remote (CDE)](https://app.zerops.io/recipes/python-hello-world.md?environment=remote-cde) - [Local](https://app.zerops.io/recipes/python-hello-world.md?environment=local) - [Stage](https://app.zerops.io/recipes/python-hello-world.md?environment=stage) - **Small Production** ← current - [Highly-available Production](https://app.zerops.io/recipes/python-hello-world.md?environment=highly-available-production) ### Services in this Environment **Services:** - **core** (core@1) - Containers: 1 × Shared Core, 0.00 GB RAM, 0 GB Disk - **app** (python@3.11) :8000 - Containers: 2 × Shared Core, 0.75 GB RAM, 1 GB Disk - Repository: [zerops-recipe-apps/python-hello-world-app](https://github.com/zerops-recipe-apps/python-hello-world-app) - **db** (postgresql@16) :5432, :6432 - Containers: 1 × Shared Core, 0.75 GB RAM, 1 GB Disk **Total Resources:** 4 containers, 2.25 GB RAM, 3 GB Disk ### One-Click Deploy (Import YAML) Use this YAML with `zcli project import` to deploy this environment: ```yaml # Small production environment offers a production-ready setup # optimized for moderate throughput. project: name: python-hello-world-small-prod services: # Production app — Zerops pulls source and zerops.yaml from the # 'buildFromGit' repo, using the 'prod' zeropsSetup. Gunicorn # serves Flask with two workers per container. # minContainers: 2 keeps at least two containers running at all # times for availability and load distribution. Zerops # autoscales within these bounds as traffic grows. - hostname: app type: python@3.11 zeropsSetup: prod buildFromGit: https://github.com/zerops-recipe-apps/python-hello-world-app enableSubdomainAccess: true minContainers: 2 verticalAutoscaling: minRam: 0.5 # Reserve ~50% of minRam free — Python/Gunicorn workers can # accumulate memory; headroom prevents OOM kills on traffic # spikes. minFreeRamGB: 0.25 # PostgreSQL single-node database. Automatic encrypted backups # are enabled by default. For higher durability, consider HA # mode or a dedicated backup strategy for production traffic. # Priority 10 ensures the database starts before the app. - hostname: db type: postgresql@16 mode: NON_HA priority: 10 verticalAutoscaling: minRam: 0.5 minFreeRamGB: 0.25 ``` --- ## Next Steps After deploying one of the environments and getting to know Zerops, you have two paths to choose from: 1. **Template Flow** — Clone our GitHub repositories and use the whole recipe as a template 2. **Integrate Flow** — If you already have an existing application on a similar stack, integrate the recipe setup with your application Select a flow: [Template Flow](https://app.zerops.io/recipes/python-hello-world.md?environment=small-production&guideFlow=template) or [Integrate Flow](https://app.zerops.io/recipes/python-hello-world.md?environment=small-production&guideFlow=integrate) Both flows are shown below: ## How to take over the Small Production environment ### 📦 Clone the template repositories Fork or clone the following repositories to your local machine or GitHub account: - [zerops-recipe-apps/python-hello-world-app](https://github.com/zerops-recipe-apps/python-hello-world-app) ### 1. Find your service name Many commands and configurations need the exact name of your service. You can find it in the Zerops Dashboard. - Open your project in the Zerops Dashboard. - In the project overview, find the service you want to manage. - Use this exact name whenever a command or pipeline configuration asks for ``. Zerops GUI: Locating the Service Name ### 2. Configure deployment pipeline Go to Service Settings > Pipelines & CI/CD Settings in the Zerops Dashboard and connect your repository. For production, use a trigger on new tags. This keeps deployments intentional and tied to a specific version. You can also add a regex filter, such as `^v[0-9]+\.[0-9]+\.[0-9]+$`, if you want to allow only semantic version tags. Zerops GUI: Triggers Alternatively, add `zcli push` to your existing CI/CD pipeline if you want full control over when deployments happen. Learn more about pipeline triggers: https://docs.zerops.io/features/pipeline ### 3. Deploy to production Create and push a new Git tag to deploy a specific version of your app: ```bash git tag -a v1.0.0 -m "Release version 1.0.0" git push origin v1.0.0 ``` > [!TIP] > Open the pipeline detail in the Zerops Dashboard to check the build progress and verify that all steps finish successfully. ### 4. Configure autoscaling Review the autoscaling settings for your runtime services and databases in Service Settings > Automatic Scaling Configuration in the Zerops Dashboard. Zerops GUI: Autoscaling configuration The most important settings are: ```yaml verticalAutoscaling: minRam: 1 minFreeRamGB: 0.5 minFreeRamPercent: 20 ``` > [!CAUTION] > Pay attention to `minFreeRamGB`. This value tells Zerops when to scale RAM vertically. Adjust it based on your app’s real memory needs. RAM scales up immediately, while CPU scales after two consecutive measurements below the threshold. > [!TIP] > Run a quick stress test with a tool like hey before real users arrive. This helps you see how your app behaves under load and tune the autoscaling settings. ### 5. Set up your domain To send real traffic to your app, configure public HTTP access in Service Settings > Public Access & Internal Ports in the Zerops Dashboard. Add your custom domain and point your DNS records to the Zerops IPs shown in the dashboard: Zerops GUI: Public access and custom domain ```text Type Name Content TTL A example.com Auto AAAA example.com Auto ``` For wildcard domains, add a CNAME record for SSL validation. Check the public access documentation: https://docs.zerops.io/features/access > [!TIP] > When changing DNS records for production, start with a low TTL value. Make sure SSL certificates are active before you disable the fallback Zerops subdomain. Once everything works, you can disable the Zerops subdomain so all traffic goes through your custom domain. --- ### 🎉 You are good to go! Your application is live in production and the core setup is complete. The following sections are optional. They cover extra production features such as log forwarding, backups, and diagnostic access. You can stop here and come back later when you need them. --- ### 6. Set up log forwarding (Optional) To send logs to an external service, go to Project Settings > Log Forwarding & Logs Overview in the Zerops Dashboard. You can forward logs to services like Better Stack, Papertrail, or your own self-hosted solution. Learn more about log forwarding: https://docs.zerops.io/references/logging ### 7. Configure database backups (Optional) Manage automated encrypted backups in Service Settings > Backups in the Zerops Dashboard. By default, backups run daily between 00:00 and 01:00 UTC. Before a major deployment, create a manual protected backup: ```bash zcli backup create --tags pre-deploy,protected ``` Read the backup documentation for more options: https://docs.zerops.io/features/backup ### 8. Set up diagnostic access (Optional) Use zCLI and VPN access when you need to inspect or maintain services directly. For runtime services: ```bash zcli vpn up ssh .zerops ``` For databases, connect through the VPN to reach the project’s private network, or set up secure direct IP access for your database admin tools. Check the VPN documentation: https://docs.zerops.io/references/cli/commands#vpn-up ## How to integrate app with Zerops ### 1. Adding `zerops.yaml` The main application configuration file you place at the root of your repository, it tells Zerops how to build, deploy and run your application. ```yaml zerops: # Production setup — install deps to ./vendor, compile nothing, # deploy minimal artifact. Flask + Gunicorn serve production traffic. - setup: prod build: base: python@3.11 buildCommands: # Install all dependencies into ./vendor so they travel # with the application artifact to the runtime container. # --target keeps packages inside the project tree (no # system-Python pollution) — matches cache and deployFiles. - pip install --target=./vendor -r requirements.txt deployFiles: - ./src # Flask application package - ./vendor # All pip-installed packages - ./migrate.py # DB migration script (runs in initCommands) # Reuse ./vendor across builds — pip skips packages already # present, cutting subsequent build times significantly. cache: - vendor # Readiness check: Zerops probes GET / before adding the new # container to the project balancer — guarantees zero-downtime # deploys only route traffic to fully-started containers. deploy: readinessCheck: httpGet: port: 8000 path: / run: base: python@3.11 # Run DB migration once per deploy version. initCommands — # not buildCommands — ensures migration and code are deployed # atomically. zsc execOnce prevents race conditions when # multiple containers start simultaneously. initCommands: - zsc execOnce ${appVersionId} --retryUntilSuccessful -- python migrate.py ports: - port: 8000 httpSupport: true envVariables: # Point Python's module search to the deployed vendor dir. PYTHONPATH: /var/www/vendor DB_NAME: db # Zerops generates these from the 'db' service hostname: # ${hostname_key} syntax references generated env variables. DB_HOST: ${db_hostname} DB_PORT: ${db_port} DB_USER: ${db_user} DB_PASS: ${db_password} # Gunicorn is the production WSGI server. Two workers handle # concurrent requests; Flask's built-in server is single-threaded # and not suitable for production traffic. start: >- /var/www/vendor/bin/gunicorn --bind 0.0.0.0:8000 --workers 2 src.app:app # Development setup — deploy full source for SSH-based iteration. # The developer SSHs in, runs the app manually, and edits files # in place. Zerops prepares the workspace; the developer drives. - setup: dev build: base: python@3.11 buildCommands: # Same vendoring as prod — ./vendor ships with deployFiles: ./ # so the developer has all dependencies ready after SSH without # running pip manually. - pip install --target=./vendor -r requirements.txt # Deploy the entire working directory — source, vendor, and # zerops.yaml (needed if the developer runs zcli push from SSH). deployFiles: - ./ cache: - vendor run: base: python@3.11 # Migration runs on deploy — database is ready when developer # SSHs in, no manual setup needed. initCommands: - zsc execOnce ${appVersionId} --retryUntilSuccessful -- python migrate.py ports: - port: 8000 httpSupport: true envVariables: PYTHONPATH: /var/www/vendor DB_NAME: db DB_HOST: ${db_hostname} DB_PORT: ${db_port} DB_USER: ${db_user} DB_PASS: ${db_password} # zsc noop keeps the container alive without starting the app — # the developer starts Flask or Gunicorn manually after SSH. # Example: /var/www/vendor/bin/gunicorn --bind 0.0.0.0:8000 # --workers 2 src.app:app start: zsc noop --silent ``` ### 🎯 What's next? **Deploy other environments** — Ready to scale? Deploy additional environments for different stages of your workflow: - [AI Agent](https://app.zerops.io/recipes/python-hello-world.md?environment=ai-agent) - [Remote (CDE)](https://app.zerops.io/recipes/python-hello-world.md?environment=remote-cde) - [Local](https://app.zerops.io/recipes/python-hello-world.md?environment=local) - [Stage](https://app.zerops.io/recipes/python-hello-world.md?environment=stage) - [Highly-available Production](https://app.zerops.io/recipes/python-hello-world.md?environment=highly-available-production) ## Knowledge Base ### Platform Reference - [Routing & Domains](https://docs.zerops.io/features/access) - [Scaling](https://docs.zerops.io/features/scaling) - [Environment Variables](https://docs.zerops.io/features/env-variables) - [CLI (zcli)](https://docs.zerops.io/references/cli) ### Service Type Reference **Python** - [Build & Deploy](https://docs.zerops.io/python/how-to/build-pipeline) - [Customize Runtime](https://docs.zerops.io/python/how-to/customize-runtime) **PostgreSQL** - [Connect](https://docs.zerops.io/postgresql/how-to/connect) - [Backup & Restore](https://docs.zerops.io/postgresql/how-to/backup) - [Manage](https://docs.zerops.io/postgresql/how-to/manage) - [Scale](https://docs.zerops.io/postgresql/how-to/scale) --- ## Related Recipes - [Zerops showcase](https://app.zerops.io/recipes/zerops-showcase.md) - [Bun Hello World](https://app.zerops.io/recipes/bun-hello-world.md) - [Go Hello World](https://app.zerops.io/recipes/go-hello-world.md) - [Java Hello World](https://app.zerops.io/recipes/java-hello-world.md)