sync is hard: building offline-first android apps from the ground up

Let’s build offline-‐first apps!

James Nocentini | Developer Advocate, Couchbase

©2014 Couchbase Inc.

Use case

2

• Clean UI

• The user shouldn’t have to be online

@jamiltz

No loading, no waiting, nothing.


Options

4

@jamiltz


Options

5

@jamiltz

6

Sync Gateway Couchbase Server


Couchbase Lite

7

Today I’d like to talk about some of the internals of Couchbase Lite Android

@jamiltz


Saving a document

8

Map<String, Object> properties = new HashMap<String, Object>();properties.put("type", "list");properties.put("title", title);properties.put("created_at", currentTimeString);properties.put("owner", "profile:" + userId);properties.put("members", new ArrayList<String>());

// save to databaseDocument document = database.createDocument();document.putProperties(properties);

@jamiltz


Saving a document

9

Document document = database.getDocument(myDocId);String title = document.getProperty("title");Map<String, Object> properties = doc.getProperties();String owner = (String) properties.get("owner");

@jamiltz


Saving a document

10

Document document = database.getDocument(myDocId);String title = document.getProperty("title");Map<String, Object> properties = doc.getProperties();String owner = (String) properties.get("owner");

@jamiltz

Plain Old Java Objects

Plain Old JSON Objects


It’s JSON

{ "_id": "123", "type": "list", "title": "TodoMVC list", "owner": "1234567890", "members": [

"0987654321","0192837465"

]}

13

@jamiltz


Content Types

JSON ❤ HTTP

14

@jamiltz


What else?

15

Replicators

@jamiltz


Two Verbs

Push → Pull ←

16

@jamiltz


Two Verbs

Push → Server Pull ← Server

17

@jamiltz


Two Verbs

Push → Couchbase Sync Gateway Pull ← Couchbase Sync Gateway

18

@jamiltz


Push

19

facebookAuthenticator = AuthenticatorFactory.createFacebookAuthenticator(accessToken);Replication push = database.createPushReplication(SYNC_URL);push.setAuthenticator(facebookAuthenticator);push.setContinuous(true);push.start();


If you were to build your own

▪ Create a job object that has an action ▪Write data to a durable queue ▪ Run a service to process the queue ▪ The service retries if the network hiccups or app crashes ▪ Remove from the queue once the job is complete

20

@jamiltz


Replicators

21

Source Target

Android App Sync Gateway

@jamiltz


Replicators

Get the sequence ID of the source database

22

@jamiltz


Replicators

23

Source Target


@jamiltz

seq: 15 seq: 5


Pull

Pull ==

24

Push

@jamiltz


Replicators

25

Source


@jamiltz

Target


Replicators

26

Source


@jamiltz

Target

seq: 15seq: 5


Pull

27

facebookAuthenticator = AuthenticatorFactory.createFacebookAuthenticator(accessToken);Replication pull = database.createPullReplication(SYNC_URL);pull.setAuthenticator(facebookAuthenticator);pull.setContinuous(true);pull.start();

Don’t drain all my battery!


Pull

30

facebookAuthenticator = AuthenticatorFactory.createFacebookAuthenticator(accessToken);Replication pull = database.createPullReplication(SYNC_URL);pull.setAuthenticator(facebookAuthenticator);pull.setContinuous(true);pull.start();


Solution

GCM is your friend 🎉

31

@jamiltz


Data Flow Techniques

32

Sync Gateway

changes feed

Push notifications worker

Continuous push

@jamiltz



33

Sync Gateway

changes feed


Continuous push

GCM notification

GCM notification

@jamiltz



34

Sync Gateway

changes feed


Continuous push

One shot pull

One shot pull

@jamiltz


Conflict resolution

36

rev-‐1

rev-‐2

rev-‐1

rev-‐2’

@jamiltz


Conflict resolution

37

rev-‐1

rev-‐2 rev-‐2’


Conflict resolution

38

rev-‐1


current revision


Conflict resolution

39

rev-‐1



Conflict resolution

40

rev-‐1

rev-‐2

current revision

P2P Demo


CouchbaseLite Listener

42

Embedded lightweight HTTP server


Replications

43

Same Replication Interface as Sync Gateway


Mesh Networks

44

Workshops

• Push / Pull • Basic config for Sync Gateway • And more…


Summary

▪ Performance

▪ Ease of development

▪ Live Queries

▪ Robustness

46


More Information

47

James Nocentini Developer Advocate @jamiltz

ToDoLite Android https://github.com/couchbaselabs/ToDoLite-‐Android

Couchbase Developer Forums http://forums.couchbase.com

mailto:@jamiltz?subject=

https://github.com/couchbaselabs/ToDoLite-Android

http://forums.couchbase.com

sync is hard: building offline-first android apps from the ground up

Mobile