Backend service for Service to Service authentication demo in Cloud Run. Complete code is present at https://github.com/kaysush/cloud-run-s2s-demo/tree/main/backend

Dockerfile

FROM node:16.13.1-stretch as build

WORKDIR /app

COPY package*.json /app/

# Install production dependencies
RUN npm install --only=production
RUN cp -a node_modules /tmp/prod_node_modules

# Now install all dependencies
RUN npm install

COPY . .

FROM gcr.io/distroless/nodejs:16
COPY --from=build --chown=nonroot:nonroot /tmp/prod_node_modules/ /app/node_modules/
WORKDIR /app
COPY . .
USER nonroot
CMD ["index.js"]

index.js

const express = require('express')
const bodyParser = require('body-parser')
const cors = require('cors')
const app = express()
app.use(cors())


const port = process.env.PORT

// Configuring body parser middleware
app.use(bodyParser.urlencoded({ extended: false }))
app.use(bodyParser.json())

app.get('/health', (req, res) => {
    res.send("This is the health endpoint.")
})

app.post("/calculate", (req, res) => {
    const request = req.body
    const x = request.x
    const y = request.y
    const operator = request.op

    switch(operator) {
        case '+': 
            var result = x + y;
            res.send(JSON.stringify({result : result}))
            break;
        case '-':
            var result = x - y;
            res.send(JSON.stringify({result : result}))
            break;
        case '*':
            var result = x * y;
            res.send(JSON.stringify({result : result}))
            break;
        case '/':
            var result = x / y;
            res.send(JSON.stringify({result : result}))
            break;
        default:
            res.status(500).send(`Operator ${operator} not supported.`);
    }
})

app.listen(port, () => console.log(`Backend started on port ${port}!`));