Develop and test Apps

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Before you begin

• A Git-based Project you can edit. Only Git-based Projects support Edit in Workspace.
• A Compute Environment with your framework installed. The transaction review App needs dash and dash-mantine-components.
• For the transaction review App, the AML Dataset and the MODEL_ENDPOINT_URL and MODEL_ACCESS_TOKEN Project environment variables from Get started.

1

Start a Workspace for the App

On the Project’s Deploy > Apps & Agents page, select Create, then App in Workspace. Domino starts a Workspace with the Project’s code. Any Workspace in the Project works the same way.

Creating an App doesn’t deploy it. Viewers see nothing until you deploy a version. If your administrator turns off the EnableAppsSDLC feature flag, which is on by default, Publish App creates and deploys the App in one step.

2

Write the entry point

An App is application code plus an entry point that starts a web server. The server must listen on 0.0.0.0, port 8888. Domino routes viewers to that port. An App that listens anywhere else fails to start.The transaction review App’s entry point is app.sh. The address and port are set in app.py:

app.sh

app.py (excerpt)

#!/usr/bin/env bash
set -euo pipefail

python app.py

Two other things in this code apply to every App. Domino serves each App under its own URL path and puts that path in DOMINO_RUN_HOST_PATH at startup. Dash, Streamlit, Flask, and any other framework that takes a base path must read it from that variable. A path assembled from the Project name or run ID stops working after a restart; see Migrate an App that builds its own path. The endpoint URL and token come from Project environment variables, not from the code.App frameworks has the launch line for Streamlit, Flask, Shiny, and static HTML. A coding assistant with Domino Skills can scaffold an App that already follows these rules.

3

Commit your changes

Commit app.py and app.sh. Preview runs the latest commit. Uncommitted edits never reach it.

4

Run the App in App Preview

In the Workspace’s App Preview tab, set the App file to app.sh, keep the AML Dataset mounted, and start the preview. These settings become the defaults when you publish, so the version you publish matches what you tested.Domino creates a Draft App for this Workspace and starts it in a private App runtime. The first load takes about as long as starting a deployed App. When the page loads, select Review next to a transaction. A score confirms that the App reached the Dataset and the endpoint.

Preview runs as you, against real Domino resources. If the Draft App starts a Job or writes to a Dataset, that happens for real. Point writes at test data and destinations while you develop.

5

Iterate with live sync

Edit the code and commit. For example, change head(20) to head(50) in review_queue() to show 50 transactions. Live sync applies the new commit to the running preview without a full restart. A preference controls whether it syncs on every commit or only when you ask.While the preview runs, you can also:

• Add query parameters to test parameterized views.
• Open the preview in its own tab at /preview/<draftAppId>. The URL works only for you.
• Read the App logs or change preview settings from the Workspace sidebar.
• Download a support bundle for the preview instance.

6

Publish

Select Publish App in the Workspace. Domino records a version from the preview settings. The Draft App and the Workspace stay as they are. Continue with Publish.

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Draft lifecycle

• Stopping the Workspace stops the preview. Administrators can also stop previews.
• Deleting the Workspace deletes the Draft App.
• Each Draft App has one preview at a time. Starting a new preview stops the old one.
• Previews don’t count against the per-Project limit on running Apps.
• Autoscaling applies to deployed versions. Test it after you deploy.

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Update an App viewers already use

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Build with coding assistants and Domino Skills

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Migrate an App that builds its own path

user    = os.environ.get("DOMINO_PROJECT_OWNER")
project = os.environ.get("DOMINO_PROJECT_NAME")
run_id  = os.environ.get("DOMINO_RUN_ID")
runurl  = f"/{user}/{project}/r/notebookSession/{run_id}/"

app = Dash(__name__, routes_pathname_prefix="/", requests_pathname_prefix=runurl)

runurl = os.environ.get("DOMINO_RUN_HOST_PATH")

app = Dash(__name__, routes_pathname_prefix="/", requests_pathname_prefix=runurl)

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Related

• Publish: Record a version of the Draft App.
• Identity: Read the viewer’s identity in your code.
• Run multiple Apps in a Workspace: Serve more than one App from one Workspace.