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Taking Cloud Databases to the Edge Cloud Computing Expo Wednesday, June 10, 2015 Bradley Holt, Developer Advocate @BradleyHolt

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Image Credit: Joan Touzet (@wohali), ASF Member, CouchDB PMC Member 2

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Image Credit: Device landscape by Jeremy Keith, on Flickr 3 Not just mobile first…!

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Image Credit: Lynn Camp Prong (Explored) by AllieKF, on Flickr 4 Offline First! Because being offline shouldn't be an error condition.!

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5 Doesn't ubiquitous connectivity make offline- enabled apps unnecessary?!

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6 No.!

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7 Quite the opposite, in fact.!

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8 Ubiquitous connectivity is driving the demand for 
 offline capabilities.!

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9 How?!

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The Eight Fallacies of Distributed Computing 1.  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 10 Text Credit: The Eight Fallacies of Distributed Computing by Peter Deutsch | Image Credit: Pneumatic Central by Sleestak, on Flickr

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11 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 12 •  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 13

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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 13

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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 13

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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 13

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Not Just Mobile Apps •  Internet of Things (Iot) •  Content delivery networks (CDNs) •  Purpose-built devices 14 Image Credit: Ethernet IoT Starter Kit

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Apache CouchDB

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Apache CouchDB •  JSON document database •  HTTP API •  Master-master replication 16

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JSON Documents 17 {
 _id: "6EF9D2B0-13D3-1378-8D30-39E3CE0B36C2",
 _rev: "1-0b457efcf82fb29492ef927ba5b6ee15",
 type: "Feature",
 geometry: {
 type: "Point",
 coordinates: [
 -71.1028,
 42.3691
 ]
 },
 properties: {
 session_id: "3486b13f-7b8a-8a96-dfbf-9b82800e367f",
 timestamp: 1422928591717
 }
 }

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CouchDB Replication 18

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CouchDB Replication Protocol •  One-off, one way operation •  Peer-to-peer (masterless) •  Incremental •  Conflict detection 19

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CouchDB Replication Protocol •  Synchronizes JSON documents between two peers over HTTP •  Implemented by: •  CouchDB •  Cloudant •  PouchDB •  Couchbase •  Implement your own: http://docs.couchdb.org/en/latest/replication/protocol.html 20

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IBM Cloudant •  Globally distributed data layer for web and mobile applications •  MongoDB-style queries •  Advanced geospatial capabilities •  Full text search indexing 21

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PouchDB

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PouchDB •  A database in your web browser •  Also works in Node.js •  Can synchronize with any database that implements the CouchDB Replication Protocol •  Makes create, read, update and delete operations extremely fast 23

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Hybrid Mobile Web Apps •  Native mobile web apps built with HTML5, CSS and JavaScript •  PouchDB includes an SQLite adapter for use in Cordova/PhoneGap •  Good for: •  Fully-featured, cross-platform native apps •  High-fidelity prototypes 24

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Responsive Mobile Web Apps •  HTML5, CSS and JavaScript mobile web apps •  Responsive design •  Enhanced to enable offline usage •  PouchDB includes IndexedDB and WebSQL adapters for use in browsers 25

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Node.js Applications •  PouchDB is installable through npm •  PouchDB includes a LevelDB adapter for use in Node.js •  In-memory and Riak-based adapters are also available •  PouchDB Server provides a Node.js server that implements the CouchDB API 26

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PouchDB Code Examples

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Installing PouchDB •  Download from the PouchDB website " •  CDN •  Bower $ bower install --save pouchdb" •  npm $ npm install --save pouchdb" 28

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PouchDB Code Examples 29 •  Creating a local PouchDB database •  Creating a remote PouchDB database •  Creating a new document •  Updating a document •  Deleting a document •  Querying a database •  Replicating PouchDB •  Listening for database changes

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Creating a Local PouchDB Database 30 var db = new PouchDB("smart-meter");" https://github.com/bradley-holt/offline-first/blob/master/pouchdb/01-create-local-database.js

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Creating a Remote PouchDB Database 31 var remoteDb = new PouchDB("https://bradley-holt.cloudant.com/smart-meter");" https://github.com/bradley-holt/offline-first/blob/master/pouchdb/02-create-remote-database.js

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Cross-Origin Resource Sharing (CORS) •  Enable Cross-Origin Resource Sharing (CORS) on remote database •  Browsers place security restrictions on cross-site HTTP requests •  If you run into a problem, remember this warning! 32 Image Credit: Grunge Warning Sign - Do Not Read This Sign by Nicolas Raymond, on Flickr

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Creating a New Document 33 var db = new PouchDB("smart-meter");" db.post({" date: "2014-11-12T23:27:03.794Z"," kilowatt_hours: 14" }).then(function() {" console.log("Document created");" }).catch(function(error) {" console.log(error);" });" https://github.com/bradley-holt/offline-first/blob/master/pouchdb/03-create-document-post.js

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Creating a New Document, Specifying its ID 34 var db = new PouchDB("smart-meter");" db.put({" _id: "2014-11-12T23:27:03.794Z"," kilowatt_hours: 14" }).then(function() {" console.log("Document created");" }).catch(function(error) {" console.log(error);" });" https://github.com/bradley-holt/offline-first/blob/master/pouchdb/04-create-document-put.js

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Updating a Document 35 db.put({" _id: "2014-11-12T23:27:03.794Z"," kilowatt_hours: 14" }).then(function() {" return db.get("2014-11-12T23:27:03.794Z");" }).then(function(doc) {" // Update the value for kilowatt hours" doc.kilowatt_hours = 15;" // Put the document back to the database" return db.put(doc);" }).catch(function(error) {" console.log(error);" });" https://github.com/bradley-holt/offline-first/blob/master/pouchdb/05-update-document.js

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Deleting a Document 36 db.put({" _id: "2014-11-12T23:27:03.794Z"," kilowatt_hours: 14" }).then(function() {" // Get the document" return db.get("2014-11-12T23:27:03.794Z");" }).then(function(doc) {" // Remove the document from the database" return db.remove(doc);" }).catch(function(error) {" console.log(error);" });" " https://github.com/bradley-holt/offline-first/blob/master/pouchdb/06-delete-document.js

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Querying a Database with allDocs" 37 db.bulkDocs([" {_id: "2014-11-12T23:27:03.794Z", kilowatt_hours: 14}," {_id: "2014-11-13T00:52:01.471Z", kilowatt_hours: 15}," {_id: "2014-11-13T01:39:28.911Z", kilowatt_hours: 16}," {_id: "2014-11-13T02:52:01.471Z", kilowatt_hours: 17}" ]).then(function(result) {" // Get all documents" return db.allDocs({include_docs: true});" }).then(function(response) {" console.log(response);" }).catch(function(error) {" console.log(error);" });" https://github.com/bradley-holt/offline-first/blob/master/pouchdb/07-query-database-all-docs.js

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allDocs Options •  include_docs" •  conflicts" •  attachments" •  startkey" •  endkey" •  inclusive_end (true by default) •  limit" •  skip" •  descending" •  key" •  keys" 38

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Querying a Database with Map/Reduce 39 •  Most queries can be done with allDocs (in PouchDB) •  Map functions transform documents into indexes •  Reduce functions aggregate results of Map functions •  _sum" •  _count" •  _stats"

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Querying a Database with PouchDB Find •  Based on Cloudant Query (Mango) •  MongoDB-style query language •  Define fields to index 40 Image Credit: Mango with section on a white background by bangdoll, on Flickr

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Replicating a PouchDB Database 41 var db = new PouchDB("smart-meter");" var remoteDb = new PouchDB(" "https://bradley-holt.cloudant.com/smart-meter"" );" https://github.com/bradley-holt/offline-first/blob/master/pouchdb/08-replicate-database.js

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Replicating a PouchDB Database 42 db.bulkDocs([" {_id: "2014-11-12T23:27:03.794Z", kilowatt_hours: 14}," {_id: "2014-11-13T00:52:01.471Z", kilowatt_hours: 15}," {_id: "2014-11-13T01:39:28.911Z", kilowatt_hours: 16}," {_id: "2014-11-13T02:52:01.471Z", kilowatt_hours: 17}" ]).then(function(result) {" …" }).catch(function(error) {" console.log(error);" });" https://github.com/bradley-holt/offline-first/blob/master/pouchdb/08-replicate-database.js

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Replicating a PouchDB Database 43 db.replicate.to(remoteDb, {" live: false," retry: false" }).on("change", function(info) {" // Replication has written a new document" console.log(info);" }).on("complete", function(info) {" // Replication has complete or been cancelled" console.log(info);" }).on("error", function(error) {" // Replication has stopped due to an unrecoverable failure" console.log(error);" });" https://github.com/bradley-holt/offline-first/blob/master/pouchdb/08-replicate-database.js

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Bidirectionally Replicating a PouchDB Database 44 Promise.all([" db.bulkDocs([" {_id: "2014-11-12T23:27:03.794Z", kilowatt_hours: 14}," {_id: "2014-11-13T00:52:01.471Z", kilowatt_hours: 15}" ])," remoteDb.bulkDocs([" {_id: "2014-11-11T22:35:01.433Z", kilowatt_hours: 11}," {_id: "2014-11-12T00:43:01.633Z", kilowatt_hours: 13}" ])" ]).then(function() {" …" });" https://github.com/bradley-holt/offline-first/blob/master/pouchdb/09-replicate-database-bidirectional.js

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Bidirectionally Replicating a PouchDB Database 45 db.sync(remoteDb, {" live: false," retry: false" }).on("change", function(info) {" // Replication has written a new document" console.log(info);" }).on("complete", function(info) {" // Replication has complete or been cancelled" console.log(info);" }).on("error", function(error) {" // Replication has stopped due to an unrecoverable failure" console.log(error);" });" https://github.com/bradley-holt/offline-first/blob/master/pouchdb/09-replicate-database-bidirectional.js

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Live Replication of a PouchDB Database 46 Promise.all([" db.bulkDocs([" {_id: "2014-11-12T23:27:03.794Z", kilowatt_hours: 14}," {_id: "2014-11-13T00:52:01.471Z", kilowatt_hours: 15}" ])," remoteDb.bulkDocs([" {_id: "2014-11-11T22:35:01.433Z", kilowatt_hours: 11}," {_id: "2014-11-12T00:43:01.633Z", kilowatt_hours: 13}" ])" ]).then(function() {" …" });" https://github.com/bradley-holt/offline-first/blob/master/pouchdb/10-replicate-database-live.js

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Live Replication of a PouchDB Database 47 var sync = db.sync(remoteDb, {" live: true," retry: true" }).on("change", function(info) {" // Replication has written a new document" console.log(info);" }).on("complete", function(info) {" // Replication has complete or been cancelled" console.log(info);" }).on("error", function(error) {" // Replication has stopped due to an unrecoverable failure" console.log(error);" });" https://github.com/bradley-holt/offline-first/blob/master/pouchdb/10-replicate-database-live.js

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Listening for Database Changes 48 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);" }).on("error", function(error) {" // changes() has errored" console.log(error);" });" https://github.com/bradley-holt/offline-first/blob/master/pouchdb/11-database-changes.js

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Listening for Database Changes 49 // Create several documents" remoteDb.bulkDocs([" {_id: "2014-11-11T22:35:01.433Z", kilowatt_hours: 11}," {_id: "2014-11-12T00:43:01.633Z", kilowatt_hours: 13}," {_id: "2014-11-12T02:42:52.284Z", kilowatt_hours: 14}," {_id: "2014-11-12T02:46:23.730Z", kilowatt_hours: 16}" }).catch(function(error) {" console.log(error);" });" https://github.com/bradley-holt/offline-first/blob/master/pouchdb/11-database-changes.js

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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/ 50

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Image Credits 51 •  Joan Touzet (@wohali), ASF Member, CouchDB PMC Member •  Device landscape by Jeremy Keith, on Flickr •  Lynn Camp Prong (Explored) by AllieKF, on Flickr •  Pneumatic Central by Sleestak, on Flickr •  Ethernet IoT Starter Kit •  Grunge Warning Sign - Do Not Read This Sign by Nicolas Raymond, on Flickr •  Mango with section on a white background by bangdoll, on Flickr

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Bradley Holt Developer Advocate bradley.holt@us.ibm.com @BradleyHolt github.com/bradley-holt