# Fn Project — Container-Native Serverless Functions Platform

> An open-source container-native serverless platform that runs functions as Docker containers on any cloud or on-prem.

## Install

Save in your project root:

# Fn Project — Container-Native Serverless Functions Platform

## Quick Use
```bash
# Install Fn CLI
curl -LSs https://raw.githubusercontent.com/fnproject/cli/master/install | sh
# Start Fn server
fn start
# Create and deploy a function
fn init --runtime go myfunc && cd myfunc
fn deploy --app myapp --local
fn invoke myapp myfunc
```

## Introduction
Fn Project is an open-source, container-native serverless platform originally created at Oracle. Every function runs inside a standard Docker container, which means any language or binary that can be packaged in a container can be used as a serverless function. It runs on any infrastructure — cloud, on-premises, or a laptop.

## What Fn Project Does
- Runs serverless functions packaged as Docker containers on any infrastructure
- Supports any programming language via Docker-based function development kits (FDKs)
- Provides hot function containers that stay warm to reduce cold start latency
- Includes a built-in flow orchestration service for composing multi-step workflows
- Exposes a REST API and CLI for function management, invocation, and monitoring

## Architecture Overview
The Fn server is a single Go binary that manages function lifecycle. When a function is invoked via HTTP, the server pulls the corresponding container image, starts it, and routes the request via stdin/stdout. Hot containers remain running between invocations to eliminate cold starts. The server stores function metadata in a SQL database (SQLite by default, MySQL/Postgres for production) and uses an LRU cache for container scheduling.

## Self-Hosting & Configuration
- Single binary or Docker-based deployment with `fn start`
- Configure a production database backend (MySQL or PostgreSQL) via environment variables
- Set up an external Docker registry for multi-node deployments
- Use `fn deploy` to push function images to a registry and register routes
- Scale horizontally by adding Fn server nodes behind a load balancer

## Key Features
- Language agnostic: any runtime that fits in a Docker container works
- Hot functions: containers stay warm across invocations to reduce latency
- Fn Flow: built-in orchestration for composing functions into workflows with error handling
- Standards-based: uses OCI container images, no proprietary packaging format
- Multi-cloud portability: runs identically on AWS, GCP, Azure, or bare metal

## Comparison with Similar Tools
- **AWS Lambda** — managed serverless locked to AWS; Fn Project is self-hosted and cloud-agnostic
- **OpenFaaS** — similar goals but uses a different function packaging model; Fn uses raw Docker containers
- **Knative** — Kubernetes-native serverless requiring a K8s cluster; Fn runs standalone with Docker only
- **Fission** — Kubernetes-focused with environment pooling; Fn is container-native without requiring K8s

## FAQ
**Q: Does Fn Project require Kubernetes?**
A: No. Fn runs directly on Docker. However, it can optionally be deployed on Kubernetes for orchestration.

**Q: How are cold starts handled?**
A: Fn keeps hot containers alive between invocations. Frequently called functions avoid cold starts entirely. Idle containers are reclaimed after a configurable timeout.

**Q: What languages are supported?**
A: Fn provides official FDKs for Go, Java, Python, Ruby, Node.js, and C#. Any language that runs in a Docker container can be used without an FDK.

**Q: Is Fn Project still maintained?**
A: The project is available on GitHub with community contributions. It is used in production at Oracle Cloud Infrastructure as the basis for Oracle Functions.

## Sources
- https://github.com/fnproject/fn
- https://fnproject.io

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Author: AI Open Source