Nodejs daemon to act as simple api | System Administration

This is a nodejs program that provides access to a backend file. It’s acting like a simple API to pick out individual lines. e.g. http://hostname:3000/daystogo/ftp.example.com

It would pick out the line in the file with ftp.example.com in it. Simple.

onst express = require('express')
const app = express()
const fs = require("fs")


// have to read data each call as the file gets changed
function readdata() {
 path = "/home/cert-api/results.csv"
 var buffer = fs.readFileSync(path,{encoding:'utf8', flag:'r'})
 var data = buffer.toString().split("\n")
 return data
}

// This takes a parameter and picks it the line out of the file
app.get('/daystogo/:url',(req, res) => {
  var output
  var data=readdata()
  output = ""
  for(let row in data) {
    if (data[row].match(req.params['url'])) {
                 output = output.concat(data[row])
    }
  }
  res.end(output)
})

app.get('/', (req, res) => {
  output=`<html>
    <head><title>Certificate API</title></head>
      <body>
        <h1>Certificate API</h1><p> 
         <li>/daystogo-h - see the whole list in human readable form</li> \
         <li>/daystogo-csv - the list in csv format</li> 
         <li>/daystogo/sample.example.com - a single entry in the file </li> </p>
      </body>
    </html> `
  res.send(output)
})

app.get('/daystogo-h',(req, res) => { 
  var output
  var data=readdata()
  output=""
  output = output.concat("<head><body>")
  output = output.concat("<table><body>")
  for (const line of data) { 
    row=line.split(",")
    output=output + "<tr>" 
    for (item in row) {
      output=output + "<td>" +  row[item] + "</td>" 
    }
  output=output + "</tr>" 
  }
  output = output.concat("</table></body></html>")
  res.send(output)
})

app.get('/daystogo-csv',(req, res) => { 
  var output
  var data=readdata()
  output = ""
  for(row in data) {
    output = output.concat(data[row])
    output = output.concat("<br>")
  }
  res.send(output)
})


const server = app.listen(3000,'cert-api.example.com', () => {
          console.log('Server ready')
})

process.on('SIGTERM', () => {
  server.close(() => {
    console.log('Process terminated')
  })
})

To make it run as a daemon on linux we creat a file /lib/systemd/system/cert-api.service

[Unit]
Description=cert-api
After=network.target

[Service]
Type=simple
User=cert-api
ExecStart=/usr/bin/node /home/cert-api/cert-api.js
WorkingDirectory=/home/cert-api
Restart=on-failure

[Install]
WantedBy=multi-user.target

And then we make this a daemon:

systemctl daemon-reload
systemctl enable cert-api --now

Leave a Reply Cancel reply