Other Frameworks

Skill: databricks-app-appkit

What You Can Build

You can deploy any Python or Node.js web application to Databricks Apps, not just AppKit projects. Streamlit, FastAPI, Flask, Gradio, Dash, Django, Next.js — they all work as long as you follow the platform’s port binding rules and dependency conventions. This page covers the configuration patterns that apply when you are not using AppKit.

In Action

“Using Python and FastAPI, configure a non-AppKit app to bind to the correct port and avoid 502 errors.”

import os
import uvicorn
from fastapi import FastAPI

app = FastAPI(title="My API")

@app.get("/health")
async def health():
    return {"status": "ok"}

if __name__ == "__main__":
    port = int(os.environ.get("DATABRICKS_APP_PORT", 8000))
    uvicorn.run(app, host="0.0.0.0", port=port)

Key decisions:

• Bind to 0.0.0.0 on the DATABRICKS_APP_PORT environment variable — this is the number one cause of 502 Bad Gateway errors when deploying to Databricks Apps
• The platform sets DATABRICKS_APP_PORT at runtime. Default to 8000, never 8080.
• Only requirements.txt (Python) and package.json (Node.js) are natively supported for dependency management
• Do not include node_modules/ in source code — each file has a 10 MB limit

More Patterns

Disabling Streamlit’s CORS and XSRF protection

“Using YAML, configure a Streamlit app to work behind the Databricks Apps reverse proxy.”

app.yaml

command:
  - "streamlit"
  - "run"
  - "app.py"
env:
  - name: STREAMLIT_SERVER_ENABLE_CORS
    value: "false"
  - name: STREAMLIT_SERVER_ENABLE_XSRF_PROTECTION
    value: "false"
  - name: DATABRICKS_WAREHOUSE_ID
    valueFrom: sql-warehouse

Both CORS and XSRF must be disabled for Streamlit to work behind the platform’s reverse proxy. Without these settings, the app loads but WebSocket connections fail, causing blank pages or frozen UIs.

Port binding for each framework

“Show the correct port configuration for Flask, Gradio, and Django.”

# Flask -- use app.yaml command instead of app.run()
# app.yaml: ["gunicorn", "app:app", "-w", "4", "-b", "0.0.0.0:8000"]

# Gradio
import os
import gradio as gr

demo = gr.Interface(fn=predict, inputs="text", outputs="text")
demo.launch(
    server_name="0.0.0.0",
    server_port=int(os.environ.get("DATABRICKS_APP_PORT", 8000))
)

# Django -- in app.yaml:
# ["gunicorn", "myproject.wsgi:application", "-b", "0.0.0.0:8000"]

Every framework must bind to 0.0.0.0 (not 127.0.0.1 or localhost) on the platform-provided port. Streamlit handles this automatically via its runtime configuration.

Understanding app.yaml versus databricks.yml

“What goes in each config file for a non-AppKit app?”

# app.yaml -- runtime config
# Controls: start command, environment variables, valueFrom resource bindings
command:
  - "uvicorn"
  - "app:app"
  - "--host"
  - "0.0.0.0"
  - "--port"
  - "8000"
env:
  - name: DATABRICKS_WAREHOUSE_ID
    valueFrom: sql-warehouse

# databricks.yml -- deployment config (only needed for DABs)
# Controls: app resource definition, target environments
resources:
  apps:
    my_app:
      source_code_path: ./src/app

For CLI-only deployments you only need app.yaml. The databricks.yml file is required only when deploying through Asset Bundles. Always run bundle deploy then bundle run when using DABs — deploy alone does not restart the app with new config.

Watch Out For

• Binding to localhost or 127.0.0.1 — the platform’s reverse proxy routes traffic to 0.0.0.0. An app bound to localhost refuses connections from the proxy, resulting in a 502 Bad Gateway.
• Using port 8080 — the platform expects your app on DATABRICKS_APP_PORT (default 8000). Port 8080 is not forwarded.
• Bundling node_modules/ in source code — individual files cannot exceed 10 MB, and node_modules/ often contains large binaries. Add dependencies to package.json and let the runtime install them.
• Customizing CORS headers — CORS headers are not configurable on the reverse proxy. Keep frontend and backend in a single app to avoid cross-origin issues. If you change egress policy, the app requires a restart for the change to take effect.