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https://github.com/petrbroz/forge-disconnected

Sample Forge application using Service Workers and Cache APIs to provide a limited offline support.
https://github.com/petrbroz/forge-disconnected

autodesk-forge express nodejs service-worker

Last synced: 30 days ago
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Sample Forge application using Service Workers and Cache APIs to provide a limited offline support.

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README 

        
# forge-disconnected



Sample [Autodesk Forge](https://forge.autodesk.com/) application using

[Service Workers](https://developer.mozilla.org/en-US/docs/Web/API/Service_Worker_API)

and [Cache](https://developer.mozilla.org/en-US/docs/Web/API/Cache) APIs to provide

a limited offline support, allowing you to cache selected models and view them

without internet connection.



Live demo is available at https://forge-disconnected.autodesk.io.



## Running locally



- Install dependencies: `npm install`

- Define your `FORGE_CLIENT_ID`, `FORGE_CLIENT_SECRET`, and `FORGE_BUCKET` env. variables

- Run the server: `npm start`

- Go to [localhost:3000](http://localhost:3000)

- After loading one of the example models, you should see a `☆` symbol next to its name,

indicating that the model can now be cached

- Click the `☆` symbol; after a moment it should change to `★`, indicating that the model

has now been successfully cached

- Go offline and open any of the models with `★` next to their name

- Click on any of the `★` symbols to clear the cache for the corresponding model



### Debugging



In Chrome, the _Application_ tab of the DevTools provides many useful tools for working

with service workers. The _Service Workers_ section shows any running workers, provides

links to their source code, and allows you to update or unregister them. In the _Cache Storage_

section you'll find the cache objects associated with the corresponding site.



Chrome - Service Workers



Chrome - Cache Objects



In Firefox, you can use the [about:serviceworkers](about:serviceworkers) or

[about:debugging#workers](about:debugging#workers) URL to get a detailed information

about service workers currently registered for various websites.



Firefox - Service Workers



## Caching strategy



Static assets and known APIs are cached immediately when the service worker is installed,

see the `STATIC_URLS` and `API_URLS` constants in the worker script.



> Note that in our case we only cache a subset of the viewer's assets, e.g., only two

environments are cached: _Sharp Highlighs_ and _Boardwalk_. If you want to include

other static assets, perhaps including your own viewer extensions, don't forget

to include them in the list.



A single document in Forge typically generates multiple derivatives, and derivatives

themselves often reference additional assets. We need a way to identify these assets

in order to cache them when needed. In this sample application, the server provides

a `GET /api/models/:urn/files` endpoint which is inspired by https://extract.autodesk.io

and - given a document URN - provides a list of URLS for all derivatives and their assets.



## Known issues & gotchas



- Service workers are only enabled in HTTPS context; one exception to this

is when serving from localhost in which case it can be HTTP

    - At one point during the development, I noticed that the service

    workers were not enabled in Google Chrome when served from http://localhost;

    as of now (with Chrome version 69.0.3497.100), localhost is working fine again

- Service worker can only manage requests in its own subpath; for example,

if you serve your service worker script from _/javascript/service-worker.js_,

it won't be able to intercept requests to _/stylesheets/main.css_