SyncedDB

SyncedDB makes it easy to write offline-first applications with real-time syncing and server-side persistence.

SyncedDB makes web applications work beautifully both online and offline.

You can write your client as if everything was stored offline! SyncedDB takes care of synchronizing the local database to other clients in real time.

Why
What
Example
Main features
How is it different
Storage options
Todo
Examples
Documentation

Why

Since the widestream adoption of IndexedDB writing web applications with full offline support has been viable. But when storing data offline web applications looses the feature of seamlessly making a users data available across devices. SyncedDB is a library that gives web applications the best of both worlds: a fully functional offline experience with real-time or on demand synchronization of data when online.

What

SyncedDB was built with the following design goal: Be as simple as possible while still providing all the features and flexibility necessary to easily create efficient and secure real-time synchronizing web applications that works offline.

SyncedDB is a lightweight layer on top of IndexedDB. It strips away all the boilerplate that the IndexedDB API requires by introducing implicit transactions, convenience methods and promises for all asynchronous operations.

Server side SyncedDB stores a list of changes that clients can request/subscribe and post/publish to. The SyncedDB client communicates with the backend through WebSockets to achieve synchronization in real time. Furthermore the client provides elegant conflict handling and events for reacting to changes published from the server.

Example

Client

var stores = {
  tasks: [ // One store named 'tasks'.
    ['byCreation', 'createdAt'] // With one index into the 'createdAt' property.
  ]
};

var db = syncedDB.open({ // Open database.
  name: 'todoApp',
  version: 1,
  stores: stores,
  remote: 'localhost:8080',
});

db.tasks.put({ // Add one task to database.
  description: 'Task description',
  finished: false,
  createdAt: Date.now()
});

db.tasks.byCreation.getAll() // Get all task elements sorted after creation.
.then(function(tasks) {
  tasks.forEach(createTaskElm);
});

db.tasks.on('add', function(e) { // A new task element pushed from remote.
  createTaskElm(e.record); // Handle task.
});

// Start syncing continously, the server will now.
// push and pull changes in real time.
db.syncContinuously('tasks');

Server

var Server = require('synceddb-server');

// Persistence with PostreSQL.
var pgPersistence = require('synceddb-persistence-postgres');

var server = new Server({
  port: 8080,
  store: new pgPersistence({
    conString: 'postgres://postgres@localhost/synceddb',
  }),
});

[See the entire example including server code here] (https://github.com/paldepind/synceddb/tree/master/examples/todo)

Main features

No additional abstractions on top of IndexedDB. It exposes the same raw power and performance but through a significantly more convenient API
Compact declarative store and index definitions with automatic upgrades
Uses promises for all async operations — even inside IndexedDB transactions
Synchronizes data through WebSockets and sends only compact diffs down the wire. This makes the network usage light and efficient.
Makes it easy and intuitive to handle conflicts.
Simple and highly flexible backend. Bring your own server-side validations, authentication, authorization, etc. Plug in any database you like and store data any way you want alongside the format that SyncedDB uses internally.

How is it different

Some libraries caters to multiple storage backends and thus ends up with a limited feature set to support the lowest common denomenator. Other implements a new database on top of the browsers native storage facilities. This highly increases complexity and reduces performance. By being a small wrapper around IndexedDB SyncedDB gains some of its key features: simplicity, power and performance.

The SyncedDB backend was designed to be as flexible as possible. Users can easily plug in any database they want, create custom message handlers at relevant points and extend the communication between the client and the server with custom messages.

State

SyncedDB is still under development. Expect rough edges.

Storage options

Currently persistence options based on the following databases are provided:

In memory (for developing)
MySQL
PostgreSQL
CouchDB

SyncedDB makes it easy to use different server side persistence strategies. These are easy to write (take a look at the existing options) and a test suite is provided.

Todo

API for IndexedDB cursors
Handle terminated connections with the server
Add more documentation and additional examples

Examples

Todo app. Demonstrates the basics of how to use SyncedDB both client side and sever side.
Authencation. Shows how the protocol between the server and the client can be extended to facilitate authentication.
Counters app. Showcases a potential conflict handling strategy where numeric changes are treated as differences/deltas.

nobuzz/synceddb