Quick Guide to Realtime Data in SSH (password-based auth) without Webhooks

Introduction

Hey there, fellow JS devs! Ever found yourself needing real-time data from an SSH connection but don't want to deal with the complexity of webhooks? Well, you're in luck! We're going to dive into how to fetch data from an SSH API using good old polling. It's straightforward, reliable, and gets the job done. Let's jump right in!

Setting up the SSH connection

First things first, let's get that SSH connection up and running. We'll use the ssh2 library because it's robust and easy to work with. Here's a quick snippet to get you started:

const Client = require('ssh2').Client;

const conn = new Client();
conn.on('ready', () => {
  console.log('Connection established!');
}).connect({
  host: 'your_server.com',
  port: 22,
  username: 'your_username',
  password: 'your_password'
});

Easy peasy, right? Just remember to handle those connection errors properly in a production environment!

Implementing the polling mechanism

Now, let's set up our polling mechanism. The idea is simple: we'll call our SSH server at regular intervals to fetch the latest data. Here's how you can do it:

function pollSSH(interval = 5000) {
  setInterval(() => {
    fetchDataFromSSH();
  }, interval);
}

function fetchDataFromSSH() {
  // We'll fill this in soon!
}

pollSSH(); // Start polling every 5 seconds

Fetching data from SSH

Time to fill in that fetchDataFromSSH function. We'll execute a command on the SSH server, grab the output, and process it. Check this out:

function fetchDataFromSSH() {
  conn.exec('your_command_here', (err, stream) => {
    if (err) throw err;
    let data = '';
    stream.on('data', (chunk) => {
      data += chunk;
    }).on('close', () => {
      const processedData = JSON.parse(data);
      updateUI(processedData);
    });
  });
}

Optimizing the polling process

Now, let's make our polling a bit smarter. We'll add some error handling and implement exponential backoff to be kind to our server:

let retryCount = 0;
const maxRetry = 5;

function pollWithBackoff(initialInterval = 5000) {
  const interval = initialInterval * Math.pow(2, retryCount);
  setTimeout(() => {
    fetchDataFromSSH()
      .then(() => {
        retryCount = 0;
        pollWithBackoff(initialInterval);
      })
      .catch((error) => {
        console.error('Error fetching data:', error);
        if (retryCount < maxRetry) {
          retryCount++;
          pollWithBackoff(initialInterval);
        } else {
          console.error('Max retries reached. Stopping poll.');
        }
      });
  }, interval);
}

Updating the user interface

Let's get that fresh data to your users! Here's a quick example using React hooks:

function SSHDataComponent() {
  const [data, setData] = useState(null);

  useEffect(() => {
    pollWithBackoff();
  }, []);

  function updateUI(newData) {
    setData(newData);
  }

  return (
    <div>
      {data ? <pre>{JSON.stringify(data, null, 2)}</pre> : 'Loading...'}
    </div>
  );
}

Best practices and considerations

1. Multiple connections: If you're handling multiple SSH connections, consider using a connection pool to manage them efficiently.

2. Large datasets: For big chunks of data, stream the response instead of collecting it all in memory.

3. Security: While we're using password auth here, consider switching to key-based authentication for better security in production.

Conclusion

And there you have it! You've now got a solid foundation for fetching real-time data from SSH using polling. It's not as fancy as webhooks, but it's reliable and gets the job done.

Remember, polling is great for many scenarios, but if you're dealing with high-frequency updates or need immediate notification of changes, you might want to explore other options.

Now go forth and poll with confidence! Happy coding! 🚀