Data Synchronization in Chrome Extensions
Serhii Kokhan
Microsoft MVP??CTO & .NET/Azure Architect??Stripe Certified Professional Developer??Offering MVP Development, Legacy Migration, & Product Engineering??Expert in scalable solutions, high-load systems, and API integrations
Introduction
Data synchronization in Chrome extensions is a common challenge, especially for various tools ranging from productivity apps to gaming aids and social media managers. In this article, we'll look at two practical methods to handle data syncing: using Chrome's storage API for a single profile and employing WebSockets for syncing data across multiple profiles. Let's dive into the details of these approaches and see how they can be effectively implemented for different types of extensions.
Ecosystem
??Google Chrome and Profiles
Google Chrome allows users to create multiple profiles. Each profile is an independent browser instance with its settings, bookmarks, history, and extensions. Profiles are useful when multiple users share the same browser or a single user wants to separate different workspaces.
??Chrome Extensions
Chrome extensions are small software programs that customize the browsing experience. They enable users to tailor Chrome functionality and behavior to individual needs or preferences. Extensions are built using web technologies such as HTML, JavaScript, and CSS.
??Extension Architecture
Google Chrome extensions consist of several components:
??Service Workers and Lifecycles
Service workers in Chrome extensions are event-driven scripts that run in the background and manage events from the browser or extension. They have no DOM access but can interact with the browser's API.
??Lifecycle
The lifecycle of a service worker in a Chrome extension is as follows:
??Runtime and Messaging
The Chrome Extension runtime is an environment that allows extensions to operate. It provides an API that includes messaging components to communicate between different parts of the extension and the web pages.
??Messaging
Chrome extensions use message passing to communicate between content scripts and background scripts/service workers.
??Extension Storage vs. Website Storage
Chrome extensions have access to several storage mechanisms:
Below are the differences between extension storage and website storage:
Chrome Storage API
The 'chrome.storage' API provides storage capabilities for Chrome extensions, offering two different storage areas: chrome.storage.sync and chrome.storage.local. These storage areas are designed to fulfill different requirements based on the extension's needs for persistence and synchronization.
??chrome.storage.local
'chrome.storage.local' is designed to store data within the local instance of a user's browser. This storage area is specific to the user's local copy of Chrome and is not automatically synchronized across different devices or instances.
Characteristics:
??chrome.storage.sync
'chrome.storage.sync' is a storage area that automatically synchronizes the stored data across all instances of Chrome where the user is signed into their Google account.
Characteristics:
Data Synchronization Strategies
??Strategy 1: Local Storage with chrome.storage.local
When developing Chrome extensions, a common requirement is to store data locally within the user's Chrome profile. The 'chrome.storage.local' API provides a straightforward and efficient way to achieve this, making it ideal for storing data that does not need to be synchronized across different devices or user profiles.
To store data locally using 'chrome.storage.local', you utilize methods to set and get key-value pairs in the local storage. This data is tied to the user's Chrome profile and is only accessible on the device where it was stored. Let's consider a React component example that leverages this API to demonstrate how this works.
In the example, we create a custom hook called 'useChromeLocalStorage' to manage local storage interactions. This hook uses React's useState and useEffect hooks to manage the state of the data. Initially, the data is set to null. When the component that uses this hook mounts, it calls 'chrome.storage.local.get' with the specified key. If it exists, this retrieves the stored data for that key and updates the state. Here's the implementation of the custom hook:
'useChromeLocalStorage.tsx'
import { useState, useEffect } from 'react';
// Custom hook to manage local storage with chrome.storage.local.
const useChromeLocalStorage = (key: string) => {
const [data, setData] = useState<any>(null);
useEffect(() => {
// Load data when the component mounts.
chrome.storage.local.get([key], (result) => {
setData(result[key]);
});
}, [key]);
const saveData = (value: any) => {
chrome.storage.local.set({ [key]: value }, () => {
setData(value);
});
};
return [data, saveData];
};
export default useChromeLocalStorage;
The saveData function within this hook stores the data under the specified key. It uses 'chrome.storage.local.set' to achieve this. If the operation is successful, the state is updated with the new data.
To use this custom hook in a React component, consider the following example:
'UserInfoComponent.tsx'
import React, { useState } from 'react';
import useChromeLocalStorage from './useChromeLocalStorage';
const UserInfoComponent: React.FC = () => {
const [userInfo, setUserInfo] = useChromeLocalStorage('userInfo');
const [inputValue, setInputValue] = useState<string>('');
const handleInputChange = (event: React.ChangeEvent<HTMLInputElement>) => {
setInputValue(event.target.value);
};
const saveUserInfo = () => {
const newUserInfo = { name: inputValue };
setUserInfo(newUserInfo);
};
return (
<div>
<h1>User Info</h1>
<input type="text" value={inputValue} onChange={handleInputChange} />
<button onClick={saveUserInfo}>Save User Info</button>
{userInfo && (
<div>
<h2>Stored User Info:</h2>
<p>{userInfo.name}</p>
</div>
)}
</div>
);
};
export default UserInfoComponent;
In this component, 'useChromeLocalStorage' is used to manage the user information. The component provides an input field for the user to enter their name. When the 'Save User Info' button is clicked, the input value is saved to 'chrome.storage.local', and the displayed data is updated accordingly.
Using 'chrome.storage.local' has several characteristics and considerations. The data is stored locally within the user's Chrome profile and is accessible only on the current device. This storage persists across browser sessions, meaning the data remains available even after the browser is closed and reopened. The storage capacity is generally large, typically up to 5MB, which is sufficient for most use cases.
However, there are a few important considerations. Data stored using 'chrome.storage.local' is not synchronized across devices, so users will only have access to their data on the device where it was stored. While the data is as secure as the user's device, developers should consider encrypting sensitive information to enhance security. Additionally, storing and retrieving large amounts of data can impact performance, so efficient data management is crucial to avoid slowdowns.
By understanding these aspects, developers can effectively utilize 'chrome.storage.local' to manage local data storage in their Chrome extensions. This approach is particularly beneficial for applications that need to store large datasets locally without the need for cross-device synchronization.
??Strategy 2: Synchronized Storage Across Multiple Instances
For users who are signed into different Google Chrome instances with the same profile account, 'chrome.storage.sync' provides a convenient way to synchronize extension data across multiple devices. This ensures that users have a consistent experience regardless of which device they are using.
The 'chrome.storage.sync' API allows you to store and synchronize data across all instances of Chrome that the user is signed into. This is particularly useful for settings, preferences, and other data that needs to be available on all devices.
To store data using 'chrome.storage.sync', you utilize methods to set and get key-value pairs in the synchronized storage. This data is tied to the user's Chrome profile and is accessible across all devices where the user is signed into Chrome with the same profile. Let's consider a React component example that leverages this API to demonstrate how this works.
In the example, we create a custom hook called 'useChromeSyncStorage' to manage synchronized storage interactions. This hook uses React's 'useState' and 'useEffect' hooks to manage the state of the data. Initially, the data is set to null. When the component that uses this hook mounts, it calls 'chrome.storage.sync.get' with the specified key. If it exists, this retrieves the stored data for that key and updates the state. Here's the implementation of the custom hook:
'useChromeSyncStorage.tsx'
import { useState, useEffect } from 'react';
// Custom hook to manage sync storage with chrome.storage.sync.
const useChromeSyncStorage = (key: string) => {
const [data, setData] = useState<any>(null);
useEffect(() => {
// Load data when the component mounts.
chrome.storage.sync.get([key], (result) => {
setData(result[key]);
});
}, [key]);
const saveData = (value: any) => {
chrome.storage.sync.set({ [key]: value }, () => {
setData(value);
});
};
return [data, saveData];
};
export default useChromeSyncStorage;
The saveData function within this hook stores the data under the specified key. It uses 'chrome.storage.sync.set' to achieve this. If the operation is successful, the state is updated with the new data.
To use this custom hook in a React component, consider the following example:
'UserInfoSyncComponent.tsx'
import React, { useState } from 'react';
import useChromeSyncStorage from './useChromeSyncStorage';
const UserInfoSyncComponent: React.FC = () => {
const [userInfo, setUserInfo] = useChromeSyncStorage('userInfo');
const [inputValue, setInputValue] = useState<string>('');
const handleInputChange = (event: React.ChangeEvent<HTMLInputElement>) => {
setInputValue(event.target.value);
};
const saveUserInfo = () => {
const newUserInfo = { name: inputValue };
setUserInfo(newUserInfo);
};
return (
<div>
<h1>User Info</h1>
<input type="text" value={inputValue} onChange={handleInputChange} />
<button onClick={saveUserInfo}>Save User Info</button>
{userInfo && (
<div>
<h2>Stored User Info:</h2>
<p>{userInfo.name}</p>
</div>
)}
</div>
);
};
export default UserInfoSyncComponent;
In this component, 'useChromeSyncStorage' is used to manage the user information. The component provides an input field for the user to enter their name. When the "Save User Info" button is clicked, the input value is saved to 'chrome.storage.sync', and the displayed data is updated accordingly.
Using 'chrome.storage.sync' has several characteristics and considerations. The data is synchronized across all instances of Chrome where the user is signed in with the same profile, ensuring consistency across devices. This storage persists across browser sessions, meaning the data remains available even after the browser is closed and reopened. However, the storage capacity for 'chrome.storage.sync' is smaller than for 'chrome.storage.local', typically limited to '100KB' per item, with a maximum of '8KB' per item, and a total quota of '102,400 bytes' for all sync data.
There are a few important considerations to keep in mind. Since 'chrome.storage.sync' has smaller storage limits, it's crucial to manage the amount of data being synchronized carefully. Additionally, there might be a slight delay in synchronization, especially if the user is switching between devices or if there are network issues, meaning that changes made on one device may not be immediately reflected on another. Also, when multiple instances of Chrome update the same data concurrently, conflicts can occur. The API attempts to resolve these conflicts, but it is essential to handle potential discrepancies in the application logic.
??Strategy 3: Real-Time Data Sync Across Profiles with SignalR
For more complex scenarios where users sign into Chrome extensions and require real-time data synchronization, 'Azure SignalR' provides a robust solution. This is common in collaborative applications where the state needs to be shared across different user sessions instantaneously. To implement this correctly in a Chrome extension, the SignalR connection should be handled in 'background.js', ensuring it remains active even when the popup is closed. The popup will then subscribe to events from background.js using the Chrome messaging API.
Setting Up SignalR Connection in background.js
First, we set up the SignalR connection in 'background.js'. This script manages the SignalR connection and listens for events, forwarding them to the popup.
'background.js'
import { HubConnectionBuilder } from '@microsoft/signalr';
const url = 'https://localhost:8080/signalr';
let connection;
const startSignalRConnection = () => {
connection = new HubConnectionBuilder()
.withUrl(url)
.withAutomaticReconnect()
.build();
connection.on('userinfo', (data) => {
chrome.runtime.sendMessage({ type: 'userinfo', data });
});
connection.onreconnecting((error) => {
if (error) {
chrome.runtime.sendMessage({ type: 'connection-error', message: error.message });
}
});
connection.onreconnected(() => {
chrome.runtime.sendMessage({ type: 'connection-reconnected' });
});
connection.onclose(() => {
chrome.runtime.sendMessage({ type: 'connection-signout' });
});
connection.start().catch((err) => console.error('SignalR Connection Error: ', err));
};
chrome.runtime.onInstalled.addListener(() => {
startSignalRConnection();
});
chrome.runtime.onMessage.addListener((request, sender, sendResponse) => {
if (request.type === 'sendMessage') {
connection.send('SendMessage', request.data).catch((err) => console.error('Sending message failed: ', err));
}
});
Creating the React Component for the Popup
Next, we handle the real-time updates in the popup by creating a React component. This component listens for messages from background.js and updates the UI accordingly.
'PopupComponent.tsx'
import React, { useState, useEffect } from 'react';
const PopupComponent: React.FC = () => {
const [inputValue, setInputValue] = useState<string>('');
const [messages, setMessages] = useState<string[]>([]);
useEffect(() => {
const handleMessage = (request: any) => {
if (request.type === 'userinfo') {
setMessages((prevMessages) => [...prevMessages, `User Info: ${JSON.stringify(request.data)}`]);
}
if (request.type === 'connection-error') {
setMessages((prevMessages) => [...prevMessages, `Connection Error: ${request.message}`]);
}
if (request.type === 'connection-reconnected') {
setMessages((prevMessages) => [...prevMessages, 'Connection Reconnected']);
}
if (request.type === 'connection-signout') {
setMessages((prevMessages) => [...prevMessages, 'Connection Signed Out']);
}
};
chrome.runtime.onMessage.addListener(handleMessage);
// Cleanup listener on component unmount.
return () => {
chrome.runtime.onMessage.removeListener(handleMessage);
};
}, []);
const handleInputChange = (event: React.ChangeEvent<HTMLInputElement>) => {
setInputValue(event.target.value);
};
const handleSendMessage = () => {
chrome.runtime.sendMessage({ type: 'sendMessage', data: inputValue });
setInputValue('');
};
return (
<div>
<h1>Real-Time Data Sync</h1>
<input type="text" value={inputValue} onChange={handleInputChange} />
<button onClick={handleSendMessage}>Send Message</button>
<div>
<h2>Messages:</h2>
{messages.map((msg, index) => (
<p key={index}>{msg}</p>
))}
</div>
</div>
);
};
export default PopupComponent;
SignalR Hub
Here is an example of a 'SignalR Hub' written in C#. This hub will handle the 'userinfo' event and other related logic.
'UserHub.cs'
using Microsoft.AspNetCore.SignalR;
using System.Threading.Tasks;
public sealed class UserHub : Hub
{
public async Task SendUserInfo(string userInfo)
{
await Clients.All.SendAsync("userinfo", userInfo);
}
public override async Task OnConnectedAsync()
{
await base.OnConnectedAsync();
// Handle connection logic if needed.
}
public override async Task OnDisconnectedAsync(Exception exception)
{
await base.OnDisconnectedAsync(exception);
// Handle disconnection logic if needed.
}
}
In this setup, the SignalR connection is managed within 'background.js' to ensure it remains active even when the popup window is closed. This is achieved by using the 'HubConnectionBuilder' with automatic reconnect enabled. The script listens for the 'userinfo' event, and when it receives this event, it forwards the data to the popup via the Chrome messaging API using 'chrome.runtime.sendMessage'. Additionally, 'background.js' handles connection status events such as reconnecting, reconnected, and connection close, and communicates these status updates to the popup as well.
The 'PopupComponent.tsx' in React uses hooks to manage the state and set up listeners for messages from 'background.js'. It listens for the 'userinfo' event and updates its state with the new data, displaying it in the UI. The component also provides an input field for the user to send messages. These messages are sent to 'background.js', which then forwards them to the SignalR hub.
The SignalR hub is defined in 'UserHub.cs', and handles incoming connections and disconnections. The hub has a method 'SendUserInfo' that broadcasts user information to all connected clients. This setup ensures that user data is synchronized in real-time across all instances where the user is signed into the Chrome extension, providing a seamless and consistent user experience.
Chrome Storage vs SignalR
Selecting the appropriate data storage and synchronization strategy for Chrome extensions is crucial for ensuring optimal performance and user experience. Each strategy has its strengths and limitations, making them suitable for different use cases. Here's a comparison table summarizing key aspects of 'chrome.storage.local', 'chrome.storage.sync', and 'SignalR'.
Synchronization Type
Data Size Limitations
Infrastructure Requirement
Real-time Updates
Offline Support
Complexity
Conflict Resolution
Ideal Use Case