Creating a Node.js serverless function as a proxy endpoint using express on Zeit Now
Serverless functions are incredibly convenient. Being able quickly and easily deply api endpoints with almost zero friction is luxurious! 🥰
One of my primary use cases for serverless functions has been to access and coordinate with third party APIs. If I'm deploying a static site with Gatsby for instance, I can user a serverless function to add dynamic features and access data across the internet without exposing tokens/secrets or dealing with CORS issues.
An egghead instructor grabbed a fun open data Star Wars quote api endpoint to use in a code demo. The trouble is, the original URL wasn't using https and wouldn't work for demo code in codesandbox.com or on egghead.io which require ssl.
The demo is baked into the videos already, the workshop is scheduled for release, and we needed a quick way to provide the endpoint and still have it function as demonstrated in the videos.
Eventually we'll want to replace the api completely for full control, but to get this solved quickly I wanted to have something under our control that could be deployed to an https endpoint and serve as a drop in proxy server for the original URL.
Here are the tools I chose:
- express to handle the request and response with convenient middleware
- axios to call the original URL being proxied
- async/await to manage the timing of ansync requests and response
- Zeit's Now for deploying configuration free serverless functions
Now is configuration free for simple problems like this. It uses a common convention and the tool inspects the /api folder for any supported files (.js in this case) and creates a serverless function for any that it discovers.
It finds randomQuote.js which becomes /api/randomQuote on the resulting url when deployed to Now.
In this case, express is being used because it has nifty middleware plugins features like cors that "just work".
When you call the endpoint, express uses a wild card to handle any incoming requests.
I've read that "express doesn't meet the model of now serverless functions" which I take to mean that you probably shouldn't build a multi-endpoint traditional express app using serverless functions.
This is good advice.
For this problem we are using a single serverless function that uses express for convenience and not to build an "express app".
When the /api/randomQuote endpoint receives any request it is captured in an async function.
app.get('*', async (req, res) => {
const response = await axios
.get('http://swquotesapi.digitaljedi.dk/api/SWQuote/RandomStarWarsQuote')
.then(({data}) => {
return data
})
res.send({
...response,
})
})
The async function assigns a constant response and awaits the response from a call to axios.get. The await keyword holds execution of the next line of code until the promise returned by axios.get is resolved. 😅
That's a lot going on in a little bit of code. async/await is a powerful way to "compress" your code which I recommend learning if it is still unfamiliar.
There's a very good egghead course from Marius Schulz on async/await in JavaScript if you'd like to learn more.
Finally, we send a response using res.send which forwards the response from the original service back to the caller with no CORS issues to suffer from and using SSL so it works where we need it.
With googling and testing the whole thing took about 20 minutes to put together and push to a live "production" endpoint.
💪