Menangani Pemutusan dan Penyambungan Kembali
Terapkan logika di sisi klien dan sisi server untuk mendeteksi pemutusan koneksi serta secara otomatis mencoba menyambung kembali.
Menangani Pemutusan dan Penyambungan Kembali adalah pelajaran WebSockets & Realtime Systems Programming gratis di CoddyKit. Ini adalah pelajaran 1 dari 4. Kamu bisa membaca pelajaran lengkapnya di bawah secara gratis — lalu praktikkan langsung di browser dengan editor kode bawaan dan tutor AI 24/7. Ini adalah bagian dari jalur belajar WebSockets & Realtime Systems Programming, dan progresmu tersinkronisasi di web dan aplikasi CoddyKit. Kursus WebSockets & Realtime Systems Programming mencakup 4 pelajaran total.
Bagian dari pelajaran ini belum diterjemahkan dan ditampilkan dalam bahasa Inggris.
Why Connections Drop
In the real world, network connections aren't always perfect. WebSockets, despite being persistent, can break due to many reasons.
Ignoring these disconnections can lead to unresponsive applications and a poor user experience. This lesson explores how to gracefully handle these interruptions.
Causes of Connection Loss
What makes a WebSocket connection drop?
- Network Issues: Wi-Fi drops, internet outages, proxy problems.
- Server Restarts: The server application might restart for updates or maintenance.
- Client Offline: The user closes their browser, loses power, or puts their device to sleep.
- Idle Timeouts: Some proxies or firewalls might close idle connections.
Client Detects Disconnects
On the client side, the browser's native WebSocket API provides events to notify you about connection status changes.
The most important event for detecting a disconnection is the onclose event. It fires when the connection is either gracefully closed by the server or abruptly lost.
Simple Reconnect Attempt
When onclose fires, you can immediately try to reconnect. This simple approach works for temporary glitches but can be problematic.
Try running this basic client-side example:
let ws;
function connect() {
ws = new WebSocket("ws://localhost:8080");
ws.onopen = () => console.log("Connected!");
ws.onmessage = (event) => console.log("Received:", event.data);
ws.onerror = (error) => console.error("WebSocket Error:", error);
ws.onclose = () => {
console.log("Disconnected. Reconnecting...");
setTimeout(connect, 1000); // Try again in 1 second
};
}
connect();Why Simple Retries Fail
Continuously trying to reconnect immediately (e.g., every 1 second) can overwhelm both the client and the server.
- Client Resource Drain: Constant connection attempts consume CPU and network resources.
- Server Overload: If many clients disconnect and then flood the server with reconnect requests, it can lead to a Denial of Service (DoS) situation.
- No Backoff: It doesn't account for prolonged outages.
Smart Reconnection: Backoff
To prevent overloading and provide a better experience, we use reconnection backoff strategies.
A backoff strategy introduces delays between reconnection attempts, and these delays typically increase with each failed attempt. This gives the server time to recover and prevents a "thundering herd" problem.
Exponential Backoff Logic
Exponential backoff is a common and effective strategy. It means the delay between retries increases exponentially.
- First retry: 1 second
- Second retry: 2 seconds
- Third retry: 4 seconds
- Fourth retry: 8 seconds
You usually cap the maximum delay to prevent excessively long waits and add some random "jitter" to avoid synchronized retries.
Client with Exponential Backoff
Let's enhance our client-side code to use exponential backoff with a maximum delay and some random jitter. Try running it!
let ws;
let reconnectInterval = 1000; // Start with 1 second
const maxReconnectInterval = 30000; // Max 30 seconds
let reconnectTimer;
function connect() {
ws = new WebSocket("ws://localhost:8080");
ws.onopen = () => {
console.log("Connected!");
reconnectInterval = 1000; // Reset on successful connection
clearTimeout(reconnectTimer);
};
ws.onmessage = (event) => console.log("Received:", event.data);
ws.onerror = (error) => console.error("WebSocket Error:", error);
ws.onclose = () => {
console.log(`Disconnected. Retrying in ${reconnectInterval / 1000}s...`);
reconnectTimer = setTimeout(connect, reconnectInterval);
reconnectInterval = Math.min(reconnectInterval * 2, maxReconnectInterval);
// Add some random jitter (e.g., +/- 10%) for better distribution
reconnectInterval += (Math.random() - 0.5) * reconnectInterval * 0.2;
reconnectInterval = Math.floor(reconnectInterval);
};
}
connect();Server-Side Disconnects
The server also needs to know when a client disconnects. This is crucial for cleaning up resources, updating connected user lists, or stopping data streams for that client.
Using a library like ws in Node.js, the WebSocket server emits a 'close' event on the individual client connection object when it disconnects.
Server Cleanup on Disconnect
Here's a basic Node.js WebSocket server example showing how to handle client disconnections and remove them from an active connections list.
const WebSocket = require('ws');
const wss = new WebSocket.Server({ port: 8080 });
let clients = new Set();
wss.on('connection', function connection(ws) {
clients.add(ws);
console.log('Client connected. Total:', clients.size);
ws.on('message', function incoming(message) {
console.log('received: %s', message);
});
ws.on('close', function close() {
clients.delete(ws);
console.log('Client disconnected. Total:', clients.size);
});
ws.send('Welcome!');
});
console.log('WebSocket server started on port 8080');Check Your Understanding
Consider a client-side WebSocket application that needs to handle disconnections robustly.
Which of the following are good practices for implementing a reconnection strategy?
Recap: Robust Connections
We've explored how crucial it is to handle disconnections in realtime applications. Both client and server play a role in maintaining connection resilience.
- Clients use
oncloseto detect disconnections. - Exponential backoff with jitter and a max delay prevents server overload during reconnections.
- Servers use
on('close')to clean up resources when clients leave.
These strategies ensure your realtime apps remain responsive and reliable, even in unstable network conditions.
Pertanyaan yang Sering Diajukan
Apakah pelajaran “Menangani Pemutusan dan Penyambungan Kembali” gratis?
Ya — teks lengkap “Menangani Pemutusan dan Penyambungan Kembali” gratis dibaca di sini di web. Untuk praktiknya secara interaktif (editor kode bawaan dan tutor AI 24/7) dan buka sisa kursus WebSockets & Realtime Systems Programming, upgrade ke CoddyKit PRO. Kursus WebSockets & Realtime Systems Programming mencakup 4 pelajaran total.
Apa yang akan aku pelajari di “Menangani Pemutusan dan Penyambungan Kembali”?
Terapkan logika di sisi klien dan sisi server untuk mendeteksi pemutusan koneksi serta secara otomatis mencoba menyambung kembali. Kamu berlatih WebSockets & Realtime Systems Programming dengan kode praktik yang langsung kamu jalankan di browser, dan tutor AI 24/7 menjawab pertanyaanmu saat kamu mengerjakan pelajaran ini.
Apakah aku perlu pengalaman untuk memulai WebSockets & Realtime Systems Programming?
Tidak diperlukan pengalaman sebelumnya. WebSockets & Realtime Systems Programming di CoddyKit dirancang untuk pemula hingga pelajar tingkat lanjut, jadi kamu bisa memulai di sini atau dari awal dan belajar sesuai kecepatan kamu sendiri. Ini adalah pelajaran 1 dari 4.
Berapa lama pelajaran “Menangani Pemutusan dan Penyambungan Kembali” memakan waktu?
Sebagian besar pelajaran CoddyKit memakan waktu sekitar 5–10 menit. Setiap pelajaran ringkas dan interaktif, jadi kamu membuat kemajuan stabil dan melanjutkan dari tempat kamu tinggalkan di web dan aplikasi.
Bisakah aku menulis dan menjalankan kode dalam pelajaran WebSockets & Realtime Systems Programming ini?
Ya. Setiap pelajaran WebSockets & Realtime Systems Programming menyertakan editor kode bawaan, jadi kamu menulis dan menjalankan kode nyata langsung di browser dan mendapatkan umpan balik AI instan — tidak diperlukan penyiapan lokal.
Semua pelajaran dalam kursus ini
- Menangani Pemutusan dan Penyambungan Kembali
- Propagasi dan Pemulihan Kesalahan yang Tangguh
- Sinyal Detak dan Penjaga Koneksi
- Konfirmasi Pesan dan Jaminan Pengiriman