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Offline-First DevelopmentGlasgowPHP – January 2016

Glynn Bird, Developer Advocate, IBM

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NoSQL…

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Relational Databases• Defined Schema

• Tables/Columns/Rows

• Constraints/Stored Procedures/Triggers

• Indexes/Views

• Structured Query Language (SQL)

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NoSQL Databases• Any database that isn't a RDBMS!• Types include:• Document stores• Key/Value stores• Graph databases• Often schemaless• Often without SQL

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…On the Move

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Image Credit: Joan Touzet (@wohali), ASF Member, CouchDB PMC Member

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Frameworks

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Image Credit: Device landscape by Jeremy Keith, on Flickr

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Not just mobile first…

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Image Credit: NASA New Horizons

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Offline First

Offline-First

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Offline, online and somewhere in-between

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The Eight Fallacies of Distributed Computing1. The network is reliable

2. Latency is zero

3. Bandwidth is infinite

4. The network is secure

5. Topology doesn't change

6. There is one administrator

7. Transport cost is zero

8. The network is homogeneous

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Text Credit: The Eight Fallacies of Distributed Computing by Peter Deutsch | Image Credit: Pneumatic Central by Sleestak, on Flickr

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Offline-first is the only way

to achieve a true, 100% always-on user

experience.**assuming the device is reliable

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Benefits of Offline First

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• Better, faster user experience, both offline and online• Allow your users to work offline or with limited connectivity• Potentially saves battery life and bandwidth usage

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Offline Patterns & Anti-Patterns• Don't return an error for no reason

• Do let users view cached/saved data

• Do synchronize data when connected

• Consider letting your users decide when to sync

• Think about the UX of users seeing stale data

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Difficulties of Offline First

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Image credit http://www.sneakerheadvc.com/wp-content/uploads/2012/02/Apple_iSync1.png

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Introducing CouchDB & IBM Cloudant

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Apache CouchDB• JSON document store

• HTTP API

• Replication

• Free, open-source

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Apache CouchDB – built to replicate• MVCC for document versioning

• Replication

• One-way or Two-way

• One-shot or continuous

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Apache CouchDB – built to replicate

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2.0

multi-node clustering

Cloudant Geo

Cloudant Query (Mango)

Cloudant Search (Lucene)

Dashboard

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IBM Cloudant – built for scale

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IBM Cloudant• Globally distributed data layer for

web and mobile applications• Run as-a-service

• MongoDB-style queries

• Advanced geospatial capabilities

• Full text search indexing

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Mobile Apps - PouchDB

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PouchDB• A database in your web browser

• Can synchronize with any database that implements the CouchDB Replication Protocol

• Makes create, read, update and delete operations extremely quickly

• Free, open-source

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Getting started with PouchDB

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<script src="https://cdn.jsdelivr.net/pouchdb/5.1.0/pouchdb.min.js"></script>

<script type="javascript">

var db = new PouchDB("smart-meter");

</script>

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Adding documents - callbacks

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db.post({ date: "2014-11-12T23:27:03.794Z", kilowatt_hours: 14}, function(err, data) { console.log(err,data);});

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Adding documents - bring your own id

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var db = new PouchDB("smart-meter");var obj = { _id: "abc123", timestamp: "2014-11-12T23:27:03.794Z", kilowatt_hours: 14};db.put(obj, callback);

https://github.com/bradley-holt/offline-first/blob/master/pouchdb/04-create-document-put.js

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Getting a document

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db.get("abc123", callback);

// calls back with // {// _id: "abc123",// _rev: "1-27695d5f483ac267d03ad0e3cb54bd2c",// timestamp: "2014-11-12T23:27:03.794Z",// kilowatt_hours: 14// }

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Getting multiple documents

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db.allDocs({include_docs:true}, callback);

// calls back with // {// "offset": 0,// "total_rows": 24,// "rows": [{...},{...}]// }

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Querying

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• Primary Index

• MapReduce

• PouchDB-find plugin

• PouchDB-quick search plugin

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Querying a Database with PouchDB Find• Based on Cloudant Query (Mango)

• MongoDB-style query language

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Image Credit: Mango with section on a white background by bangdoll, on Flickr

db.find({ selector: { name: 'Mario' debut: { '$gt': 1990 } }, fields: ['_id', 'lastname'], sort: ['lastname']})...

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Replicating a PouchDB Database

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var db = new PouchDB("smart-meter");var remoteDb = new PouchDB("https://bradley-holt.cloudant.com/smart-meter");db.replicateTo(remoteDb);

https://github.com/bradley-holt/offline-first/blob/master/pouchdb/08-replicate-database.js

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Bidirectionally Replicating a PouchDB Database

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db.sync(remoteDb).on("change", function(info) { // Replication has written a new document console.log(info); }).on("complete", function(info) { // Replication has completed or been cancelled console.log(info); });

https://github.com/bradley-holt/offline-first/blob/master/pouchdb/09-replicate-database-bidirectional.js

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Listening for Database Changes

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var changes = remoteDb.changes({ since: "now"}).on("change", function(change) { // A document has changed console.log(change);}).on("complete", function(info) { // changes() was canceled console.log(info);});

https://github.com/bradley-holt/offline-first/blob/master/pouchdb/11-database-changes.js

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PouchDB Framework Adapters

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Web Apps Going Offline

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HTML5 Offline Application Cache• Enables fully-functional offline

web apps

• Stores files and assets for offline browsing

• Makes page loads very fast, even when online

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Cache Manifest File

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<html manifest="example.appcache"> …</html>

CACHE MANIFEST# v1 - 2015-01-08index.htmllogo.pngapp.cssapp.js

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Service Workers (Beta)

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Client-side scripting framework for

•programmable cache

•sync

•push messaging

•geo-fencing

•background tasks

https://jakearchibald.github.io/isserviceworkerready/

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Hybrid or Responsive Mobile Web Apps

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Hybrid Mobile Web Apps• Native mobile web apps built with

HTML5, CSS and JavaScript

• Good for:• Fully-featured, cross-platform native apps

• High-fidelity prototypes

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Responsive Mobile Web Apps• HTML5, CSS and JavaScript mobile

web apps

• Responsive design

• Enhanced to enable offline usage

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Native iOS & Android Apps

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Cloudant Sync• Library for iOS and Android

• Provides local storage and query API

• Optional sync to Cloudant

• Open-source and free to use

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Cloudant Sync• Stores data using SQLite

• TouchDB provides MVCC

• Replication to Cloudant over HTTPS

• Cloudant Query API

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Getting started with Cloudant Sync - iOS

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CDTDatastore *ds = [manager datastoreNamed:@"mydb" error:&error];

pod "CDTDatastore"

• Install library

• Create database

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Creating data Cloudant Sync - iOS

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CDTDocumentRevision *rev = [CDTDocumentRevision revisionWithDocId:@"doc1"];

rev.body = [@{ @"description": @"Buy milk", @"completed": @NO, @"type": @"com.cloudant.sync.example.task"} mutableCopy];

CDTDocumentRevision *revision = [ds createDocumentFromRevision:rev error:&error];

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Fetching data - Cloudant Sync - iOS

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CDTDocumentRevision *retrieved = [datastore getDocumentWithId:@"doc1" error:&error];

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Indexing data - Cloudant Sync - iOS

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// create index on name, age and pet species NSString *name = [ds ensureIndexed:@[@"name", @"age", @"pet.species"] withName:@"basic"]

// create full-text index on name and comment NSString *name = [ds ensureIndexed:@[@"name", @"comment"] withName:@"basic_text_index" type:@"text"];

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Querying data - Cloudant Sync - iOS

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NSDictionary *query1 = @{ @"pet.species": @"cat" };

NSDictionary *query2 = @{ @"$or": @[ @{ @"pet.species": @{ @"$eq": @"dog" } }, @{ @"age": @{ @"$lt": @30 } } ]};

CDTQResultSet *result = [ds find:query];

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Getting started with Cloudant Sync - Android

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repositories { mavenLocal() maven { url "http://cloudant.github.io/cloudant-sync-eap/repository/" } mavenCentral()}

dependencies { compile group: 'com.cloudant', name: 'cloudant-sync-datastore-core', version:'0.14.0' compile group: 'com.cloudant', name: 'cloudant-sync-datastore-android', version:'0.14.0'}

• Install library

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Creating a database - Cloudant Sync - Android

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import com.cloudant.sync.datastore.*;

// Create a DatastoreManager using application internal storage path…

Datastore ds = manager.openDatastore("mydb");

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Storing data - Cloudant Sync - Android

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MutableDocumentRevision revision = new MutableDocumentRevision();

Map<String, Object> body = new HashMap<String, Object>();

body.put("animal", "cat");

revision.body = DocumentBodyFactory.create(body);

BasicDocumentRevision saved = ds.createDocumentFromRevision(revision);

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Pro Forma• Define fields you want to collect

• Renders form saving data to PouchDB

• Replicates data to Cloudant

• Demohttps://glynnbird.github.io/proforma/

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MD• Offline word processor

• Saves Markdown documents to PouchDB

• Replicates data to Cloudant

• Demohttp://mddoc.mybluemix.net/

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Gutenberg• Offline e-book reader

• Replicates book list from server

• Each book is a Cloudant database

• Demohttp://glynnbird.github.io/gutenberg/

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www.glynnbird.com• My home page

• Cloudant database of articles

• Replicated to PouchDB

• Appcache for offline first

• http://www.glynnbird.com/

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Volt• Password vault in a Chrome

extension

• Data stored in encrypted in PouchDB

• Optional back to CouchDB/Cloudant

• https://github.com/glynnbird/volt

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Location Tracker• Stores data locally in PouchDB

• Front end built with AngularJS

• Authentication logic built with Node.js

• User interface built with Leaflet

• Replicates location data to Cloudant

• More info:https://cloudant.com/location-tracker/

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@glynn_bird

Glynn BirdDeveloper Advocate, Cloud Data Servicesglynn.bird@uk.ibm.com@glynn_birdgithub.com/glynnbird

@glynn_bird

Image Credits

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• Joan Touzet (@wohali), ASF Member, CouchDB PMC Member<https://twitter.com/wohali/status/595689720933445632>

• Device landscape by Jeremy Keith, on Flickr<https://www.flickr.com/photos/adactio/6153481666>

• NASA New Horizons<https://www.nasa.gov/sites/default/files/thumbnails/image/nh-surface.jpg>

• Pneumatic Central by Sleestak, on Flickr<https://www.flickr.com/photos/dlanod/235990854>

• Mango with section on a white background by bangdoll, on Flickr<https://www.flickr.com/photos/bangdoll/5665235102>

• Grunge Warning Sign - Do Not Read This Sign by Nicolas Raymond, on Flickr<https://www.flickr.com/photos/80497449@N04/7417352980>