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EC2 FastAPI Deployment Notes
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PROJECT: Blog Writing Agent
STACK: FastAPI + uv + systemd + GitHub Actions CI/CD


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1️⃣ Create systemd Service File
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Command:
sudo nano /etc/systemd/system/blog-agent.service

Why?
- /etc/systemd/system/ is system-level directory
- Normal user cannot create files here
- sudo required for admin access
- This file defines how our app runs as a service


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2️⃣ Service File Content
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[Unit]
Description=Blog Agent FastAPI App
After=network.target

[Service]
User=ubuntu
WorkingDirectory=/var/www/blog-agent
ExecStart=/home/ubuntu/.local/bin/uv run uvicorn Application.app:app --host 0.0.0.0 --port 8000
Restart=always

[Install]
WantedBy=multi-user.target


Why each line?

User=ubuntu
→ Runs app as ubuntu user (safer than root)

WorkingDirectory
→ Tells system where project exists

ExecStart
→ Exact command to start FastAPI app

Restart=always
→ If app crashes, systemd restarts it automatically

WantedBy=multi-user.target
→ Makes service start when system boots


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3️⃣ Reload systemd
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Command:
sudo systemctl daemon-reload

Why?
- After creating new service file
- systemd must reload configuration
- Otherwise it won’t detect new service


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4️⃣ Enable Service (Auto Start on Reboot)
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Command:
sudo systemctl enable blog-agent

Why?
- Makes app start automatically when server reboots
- Without this, service won’t auto start


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5️⃣ Start Service
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Command:
sudo systemctl start blog-agent

Why?
- Immediately start app without reboot


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6️⃣ Check Status
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Command:
sudo systemctl status blog-agent

Why?
- Verify if service is running
- Shows logs and errors if any


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7️⃣ Restart During Deployment (Used in CD)
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Command:
sudo systemctl restart blog-agent

Why?
- After git pull & uv sync
- Restart loads latest code
- Clean exit code (no 143 error)
- GitHub Actions shows GREEN ✔


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🚀 Why We Stopped Using nohup & ?
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Problem:
- SSH session close → background process killed
- GitHub showed "Process exited with status 143"
- Deployment looked failed even though server updated

Solution:
- Use systemd service
- App runs independently of SSH
- Clean process management
- Production ready setup


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🎯 Final Deployment Flow
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GitHub Push
   ↓
CI Run (Tests)
   ↓
CD SSH into EC2
   ↓
git pull origin main
uv sync
sudo systemctl restart blog-agent
   ↓
App Updated Successfully


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🔥 Important Concepts Learned
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✔ Difference between normal user & root
✔ What sudo does
✔ What systemd is
✔ Why production apps use services
✔ Why background (&, nohup) is not production safe
✔ Why exit code 143 happens
✔ Proper CI/CD deployment architecture


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🏆 Result
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App:
- Auto restarts if crashed
- Auto starts on server reboot
- Independent of SSH
- Clean GitHub deployment (Green tick)

Production-level deployment achieved.