Part XI: Custom code and microservices

Not all requirements for an app will be met by the Hasura APIs. Custom APIs and microservices like API integrations or UI microservices will always be needed to be added specifically to the project.

Hasura provides easy ways to deploy custom microservices by either specifying docker images or by directly pushing code via git.

Let us explore the 2 use cases:

Custom code: Adding a simple web-server to serve a UI

We’ll use a Nodejs Express microservice for the server. To do this, we’ll use the api microservice from the hello-nodejs-express hub project as the base (it is basically a nodejs-express microservice boilerplate).

Initialize the microservice using:

# in the project directory
$ hasura microservice clone api --from hasura/hello-nodejs-express

This will create a directory called api inside your microservices directory, which will contain a k8s.yaml file, a Dockerfile and the source code for the Nodejs Express server.

The k8s.yaml file contains the Kubernetes specs for the microservice. The Dockerfile is used by the Hasura platform to automatically build your code in the right environment.

Now let us modify the /microservices/api/src/server.js file to just serve one sample request. Update the contents of the file with:

var express = require('express');
var app = express();

app.get('/', function (req, res) {
  console.log('Request received');
  res.send('Hello! The api microservice is now deployed!');

app.listen(8080, function () {
  console.log('Example app listening on port 8080!');

Add a route to conf/routes.yaml so that the microservice can be reached externally:

$ hasura conf generate-route api >> conf/routes.yaml

Generate and add a remote to conf/ci.yaml to add continuous integration (deploy code using git-push):

$ hasura conf generate-remote api >> conf/ci.yaml

Once this is done, we’re ready to push!

# in project directory
$ git add .
$ git commit -m "added api microservice"
$ git push hasura master

Voila, our microservice is deployed and live at https://api.<cluster-name>! In case there are any errors in building or deploying our code, the git push command will show you errors and the push will fail. You’ll have to fix the errors, commit and push again!

You can add more code to the above nodejs-express app to build a proper UI and then simply commit and git push to redeploy.

Behind the scenes

The Hasura platform basically builds a docker image from the latest git changes pushed by you, and deploys the corresponding kubernetes microservice underneath.

Docker: Adding a custom database browser (adminer)

You can also add microservices from Docker images. For example, let’s try to generate an adminer microservice using clue/adminer.

# in project directory
$ hasura microservice generate adminer --image clue/adminer --port 80

This will create a directory inside the microservices directory called adminer which will contain a k8s.yaml file. This file describes the Kubernetes configuration for our microservice including the docker image details.

Next, to expose this service externally, generate a route and add it to conf/routes.yaml

$ hasura conf generate-route adminer >> conf/routes.yaml

Once this is done, we’re ready to push!

# in project directory
$ git add .
$ git commit -m "added adminer microservice"
$ git push hasura master

That’s all you need to do. If you head to https://adminer.<cluster-name> you’ll see the familiar adminer UI.

Automatic SSL certificates

The Hasura platform automatically creates Grade A SSL certificates using LetsEncrypt.

The SSL certificate creation can take a few minutes. During this time https://adminer.<cluster-name> will not be served, and you’ll have to access your microservice on http instead. As soon as the certificate is ready, will automatically start redirecting to the https version.

Next: Using the Auth UI Kit

Next, head to Part XII: Using the Auth UI Kit.