Jinja2 Templates for DevOps Automation

What is Jinja2?

Jinja2 is a templating language used by Ansible, SaltStack, Helm (via Sprig), and countless Python web frameworks. It uses {{ variable }} for interpolation and {% for %} / {% if %} for control flow.

DevOps Use Cases

Dynamic Kubernetes Manifests

# deployment.j2
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ app_name }}
spec:
  replicas: {{ replicas | default(2) }}
  template:
    spec:
      containers:
        - name: {{ app_name }}
          image: "{{ image }}:{{ tag }}"
          env:
            {% for key, value in env_vars.items() %}
            - name: {{ key }}
              value: "{{ value }}"
            {% endfor %}

Nginx Config Generation

Generate server blocks for multiple domains without copy-pasting:

{% for domain in domains %}
server {
    server_name {{ domain }};
    location / { proxy_pass http://{{ backend }}; }
}
{% endfor %}

Using the API

curl -X POST https://api.toolkitapi.io/v1/devtools/jinja2-render \
  -H "X-API-Key: $API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "template": "Hello {{ name }}!",
    "variables": { "name": "World" }
  }'

Filters

Jinja2 filters transform values inline:

Sandbox Mode

The API renders templates in a sandboxed environment — no filesystem access, no __import__, no subprocess calls. It is safe to render user-supplied templates.