Implementing data synchronization between IndexedDB and CouchDB

01 Oct 2023

In modern web applications, offline support and data synchronization have become crucial features. One common scenario is to synchronize data stored locally in the IndexedDB browser database with a remote database like CouchDB.

In this blog post, we will explore how to implement data synchronization between IndexedDB and CouchDB using JavaScript and the PouchDB library.

Prerequisites

To follow along with this tutorial, you should have some basic knowledge of JavaScript, IndexedDB, and CouchDB. You will also need to have the following dependencies installed:

PouchDB library: npm install pouchdb

Setting up IndexedDB

To get started, let’s create an IndexedDB database and define an object store to store our data. We’ll assume you already have a basic understanding of IndexedDB concepts.

// Open the IndexedDB database
const openDatabase = indexedDB.open("myDB", 1);

openDatabase.onupgradeneeded = function (event) {
  const db = event.target.result;

  // Create an object store to hold our data
  const objectStore = db.createObjectStore("myStore", { keyPath: "id" });

  // Define indexes for searching or sorting
  objectStore.createIndex("name", "name", { unique: false });
};

openDatabase.onsuccess = function (event) {
  const db = event.target.result;

  // Perform operations on the database
};

Synchronizing with CouchDB using PouchDB

Next, we’ll use the PouchDB library to handle the synchronization between IndexedDB and CouchDB. PouchDB is a JavaScript library that provides an API similar to IndexedDB but with additional features for syncing data with CouchDB.

First, we need to create a new PouchDB instance and initialize the sync with our CouchDB database:

// Create a new PouchDB instance
const localDB = new PouchDB("myDB");

// Initialize the sync with CouchDB
localDB.sync("http://localhost:5984/myDB", {
  live: true,
  retry: true,
});

This code will create a new PouchDB instance connected to the local IndexedDB database called “myDB”. We then initiate a sync between the local database and the remote CouchDB instance.

Now, whenever we insert, update, or delete documents in the local IndexedDB database, PouchDB will automatically sync those changes with CouchDB.

Handling Sync Conflicts

Sync conflicts can occur when changes are made to the same document in both the local IndexedDB and CouchDB. PouchDB provides a way to handle these conflicts using conflict resolution functions.

To handle conflicts, we can define a conflict resolution function when setting up the sync:

const conflictResolution = function (localDoc, remoteDoc) {
  // Decide which version of the document to keep
  return localDoc;
};

localDB.sync("http://localhost:5984/myDB", {
  live: true,
  retry: true,
  conflicts: conflictResolution,
});

In the above example, we are resolving conflicts by keeping the local version of the document. You can define your own conflict resolution logic based on your application requirements.

Conclusion

Implementing data synchronization between IndexedDB and CouchDB is essential for ensuring offline capability and data consistency in web applications. By using the PouchDB library, we can easily handle synchronization and conflict resolution.

In this blog post, we covered the basics of setting up IndexedDB, initializing a sync with CouchDB using PouchDB, and handling sync conflicts. Armed with this knowledge, you can now start building robust and seamless offline applications.

#webdevelopment #databases