---
title: Demo Script
order: 3
description: A guided tour of the harness for presenters.
icon: lucide:presentation
---

# Demo Script

Use the harness to show Lens in about ten minutes. Start it with `harness/start.sh` and open `http://localhost:8085`. See [Development](contributing.md#the-harness).

## 1. The healthy page

Open `/orders.bxm`. Point at the collapsed strip: status, time, memory, query and template counts.

![The collapsed health strip](../assets/screenshots/strip-collapsed.png)

Press ``Ctrl+` `` to open the panel. Show the Timeline, then press `3` for Queries, and the Timers and Messages tabs.

## 2. An N+1

Open `/n-plus-one.bxm`. The bar only says what happened: 11 queries, no color. Show the queries and their caller in Queries, then press **Console** to open the request in the console, where the N+1 issue is listed.

![The N+1 page in the console, with its issues](../assets/screenshots/issues.png)

## 3. A slow query

Open `/slow.bxm`. Show the slow query on the Timeline, then the Slow query issue in the console request detail.

## 4. A caught exception

Open `/caught-exception.bxm`. Lens opens the panel on Exceptions by itself. Open Exceptions to show the stack and the editor link.

## 5. An uncaught error

Open `/error.bxm`. Core shows its own page, so there is no bar. Open the console Requests page to show the request, its exception and its issue.

## 6. History

Visit `/api/orders.json.bxm` and `/events.bxm`, then open the console Requests page. Show the JSON and SSE rows with their type. Mention the 50 request ring buffer and that nothing is saved.

## 7. HTTP and the runtime

Open `/http.bxm` and show the 404 in HTTP. Open the Runtime tab to show the versions, the heap and the main settings, then the console Configuration page.

## 8. Redaction

Open `/forms.bxm`, submit the form and open Request and Scopes. The password value is masked. Open `/session.bxm` and show the masked token.

## 9. Extend it

Open `/extend.bxm`. Show the Harness and Phases panels built from app code, and the Demo module panel from `demoLens`.

![The Harness panel](../assets/screenshots/extend.png)

## 10. The UI

Drag the top edge to resize, press the detach button to float the panel, then dock it again. Toggle the theme. Reload the page and show that the state persists.

![The detached floating window](../assets/screenshots/popout.png)

## 11. The console

Open `http://localhost:8085/~bxlens/index.bxm` and sign in with `lens-demo`. Start on Overview, then open Requests and pick the N+1 request you made earlier. Click Open console in the bar and the More menu to show the link from a page to its request.

![The console Requests page](../assets/screenshots/console-requests.png)

## 12. Executors and tasks

Open `/load.bxm`, then the Executors page. The `demo-pool` goes degraded and then critical as eight tasks queue on two threads. Open Tasks, pick `sync-prices`, press Run now and show the error. Pause and resume `cleanup-sessions`.

![A task run in the console](../assets/screenshots/console-task-run.png)

## 13. A slow request

Open `/stall.bxm`, then open the request in the console. The Slow request issue names the line where the request was after 3 seconds. The Request tab of the bar shows the CPU time and the memory.

## 14. Design the bar

Open the Bar designer, hide a tab, move another, save, and reload a page. Press Reset to default.

![The Bar designer](../assets/screenshots/console-designer.png)