💡 What is Jinja?

🧙‍♂️ Jinja is a modern and designer-friendly templating language for Python, used to generate files dynamically. Think of it like Mad Libs for config files, where you can inject variables into a template and programmatically generate output.

It’s used heavily in:

• Any scenario where you want to avoid copy-paste hell 🔥
• Infrastructure as Code (Ansible, SaltStack)
• Web frameworks (like Flask or Django)
• Easy to learn if you have experience some template engine such as Laravel Blade, Twig, Haml, 11ty

🎯 Why Use Jinja?

Use Jinja when you want to:

• Reduce human errors by avoiding repetitive copy-paste
• Dynamically change parameters like server names, ports, or environments
• Reusable: You can write once and render thousands of variations. Efficiency FTW.
• Clean separation: Keeps logic out of your final output, whether it’s HTML or NGINX configs.
• CLI support (jinja-cli)
• Make your deployments look like wizardry ✨

❌ Don't Use Jinja

Example: Automating NGINX Config with Jinja

Let’s break it down with an imaginative metaphor:

"Using vim for 1,000 NGINX config files is like writing wedding invitations by hand. Sweet, but painful." Jinja is like a laser printer with your best handwriting.

Scenario: You run a massive fleet of servers and each one needs its own NGINX configuration:

Without Jinja:

→ vim  
 → Modify 
  → Save
→ Repeat 999 times 🔁
 → Cry 😭

With Jinja:
 

 You write one template:

# nginx_template.j2
upstream {{ upstream }} {
  {% for upstream_item in upstream_servers%}
    {{- upstream_item }};
  {% endfor %}
}
server {
  listen 80;
  server_name {{ domain_name }};
  rewrite ^(.*) https://$host$1 permanent;
}
server {
  listen 443 ssl http2;
  listen [::]:443 ssl http2;
  server_name {{ domain_name }};
  server_tokens off;
  ssl_certificate /etc/letsencrypt/live/{{ domain_name }}/fullchain.pem;
  ssl_certificate_key /etc/letsencrypt/live/{{ domain_name }}/privkey.pem;
  client_max_body_size 50M;
  access_log /var/log/nginx/{{ domain_name }}-access.log;
  error_log /var/log/nginx/{{ domain_name }}-error.log;
  {%- if auth %}
  auth_basic {{ auth.auth_basic }};
  auth_basic_user_file {{ auth.auth_user_file }};
  {% endif -%}
  location / {
    access_log /var/log/nginx/{{ domain_name }}-access.log;
    proxy_pass {{ upstream }};
    proxy_redirect off;
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;
    proxy_set_header X-Forwarded-Host $host;
    proxy_set_header X-Forwarded-Port $server_port;
  }
}

With dynamic data with json

app.local.json
{
  "domain_name" : "app.local",
  "upstream" : "http://proxy-app",
  "upstream_servers" : [
    "server 10.143.41.104:8081",
    "server 10.143.41.104:8082",
    "server 10.143.41.104:8083"
  ],
  "auth" : {
    "auth_basic" : "Restricted Area",
    "auth_user_file" : "/etc/nginx/htpasswd/auth"
  }
}

Run-time 🏃

jinja2 ./nginx_template.j2 ./app.local.json --format=json --outfile=./app.local.conf

Now you’ve got a thousand configs generated faster than a barista can spell your name wrong.

Final Thoughts

Jinja is the unsung hero of DevOps, backend automation, and lazy (smart) developers everywhere. It’s not flashy, but it’s reliable, fast, and scales beautifully. 🚀

Use it wisely — and maybe, just maybe, save your fingers from vim-induced arthritis.

Full content:Dev.to
Demo:Github