I had initially developed an application with Angular frontend and Sails JS backend. However, I recently separated some of the backend functions into a micro-service using Express. Now, I am looking for guidance on how to call these functions from my main application. Can anyone provide me with instructions on how to achieve this?
Here are a couple of methods to achieve this:
CORS
To ensure your microservice can freely communicate with the browser, you need to enable CORS. In Express, this can be accomplished as follows:
const cors = require('cors');
app.use(cors());
If the endpoint requires credentials (e.g., login), additional options may need to be set for CORS:
app.use(cors({
credentials: true,
origin: true,
methods: 'POST,GET,PUT,OPTIONS,DELETE'
}));
For more details on configuring the cors middleware, refer to the documentation at: https://www.npmjs.com/package/cors
Application Gateway
An alternative approach is to run all your microservices behind a reverse proxy like Nginx, Apache2, or HAproxy. This method was commonly used by Amazon pre-2014 (before browsers supported CORS).
Below is a basic example of an Nginx configuration for proxying your microservice:
# The ^~ operator matches all urls that begin with the specified string:
location ^~ /some/microservice {
proxy_pass http://some.microservice.myapp.com;
}
An Application Gateway, as it's known in the industry, acts as a reverse proxy that maps multiple microservices to URL paths under a single domain name. Apart from enabling cross-origin requests, these gateways offer benefits like load balancing and firewall protection for internal servers.
Regardless of the approach you choose, fetching data from your microservices involves making AJAX requests using either traditional XMLHttpRequest or the modern fetch API:
// If CORS is properly configured on your server:
fetch('https://some.microservice.myapp.com/getdata')
.then(function(response) {
return response.json();
})
.then(function(result) {
console.log(result);
});
// When utilizing an application gateway:
fetch('https://myapp.com/some/microservice/getdata')
.then(function(response) {
return response.json();
})
.then(function(result) {
console.log(result);
});
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