First published on MSDN on Aug 21, 2018
In an earlier article:
How to operationalize TensorFlow models in Microsoft Machine Learning Server
, we showed how you can deploy a TensorFlow image classification model pre-trained using ImageNet as service in Machine Learning Server, and download a Swagger specification of the service as a JSON file, which can be passed on to app developers who will use it to generate a client for consuming the service.
In this article, we will walk through the process of consuming an ML service from a single-page app (SPA) built using the popular progressive web apps (PWA) framework
. At a very high level, it involves:
Generating API client from the Swagger JSON file of the service
Linking in the client as npm module package
We can use the
Vue.js webpack template
to scaffold our project. The webpack template is part of the vue-cli, which can be installed through:
Once that's installed, we can run the following commands to create our project and run it. For this example, let's use "ml-app-vuejs" as the name of our app.
At this point, you should be able to point your browser to http://localhost:8080 and see a responsive Vue.js web app. You can change the browser to a responsive mode through the dev tools and see how the app renders on mobile.
After that, inspect the "node_modules" folder, and you should see a link named "image_classification" there. In addition to linking in the package, we also need to disable AMD loader through "webpack.base.conf.js" to avoid potential module loading error:
In this example, all API requests are sent to the same domain where the web app is hosted and then proxied (see "proxyTable" in "config/index.js") to Machine Learning service. In production, API requests can be re-routed to the API servers using reverse proxy, or you can also
enable CORS to allow cross-domain API requests
from the web app in the browser directly.
To proxy the API calls the Machine Learning service, we need to update "config/index.js" to have the following:
Implementing the Login Screen
In order to consume the ML service to perform image classification, we need an access token. So, we will implement a login screen, where the the app will acquire an JWT access token using the credentials provided by the user on the login screen.
Go to "src/router/index.js" to wire up the component we just created to the main "App.vue". It should look like this:
To actually call the login API and obtain an JWT access token, we need to update the "login" function above to:
For details on the usage and code example of the "image_classification" module, consult the
of the generated client.
At this point, you should be able to login and see a login request in the dev tools coming back with an access token.
Implementing the Image Classification Screen
For image classification, we will let the user provide an image, and the app will draw it out on a canvas, then base64 encode the image to a string, because we will be sending it in JSON format to the API. If you recall from the
, the service deployed already understands the encoding and it will decode it properly to pass onto the TensorFlow model.
Here's the HTML elements to be added to the "template" and right after the "login-container" div:
Again, usage and sample code for "
" can found in the documentation inside the generated client package.
The Final Product
Here's what the final product looks like, slightly styled using Bootstrap.