MOBILE APPLICATIONS AND CLOUD COMPUTING Roberto Beraldi
Course Outline • 6 CFUs • Topics: • Mobile application programming (Android) • Cloud computing • To pass the exam: • Individual working and documented application in android (possibly using cloud services) • Answer to 3 of general questions
Key terms • Cloud computing � • Delivery of remote virtual resources through internet (virtual machines, storage space, software functions (web api) , data – e.g. open data, etc..) • Mobile Applications • app that runs on mobile devices � smartphone • App running on wearable devices, e.g., smartwatch • Context-Awareness • sensors • Where (lat,lon) the device running the application is located • Other Sensors, e.g., acceleration, orientation, etc • Connection and synergy between Cloud and Mobile devices/applications is possible
Cloud computing and mobile applications • Cloud computing is an umbrella term to refer to a way to access functionalities remotely (e.g., via Internet) • There are different ‘delivery models’ of cloud computing • Software as a Service (SaaS) or Web API • Platform as a Service (PaaS) • Infrastructure as a Service (Iaas) (virtualization) • Cloud computing can be used ‘alone’, or… • Cloud computing, or more simply ‘cloud’, can be exploited by mobile apps. This can be done in different ways • One simple possible way is to synchronize data views of different devices (fixed or mobile)
Dropbox • Dropbox is a free (up to 2GB), web-based cloud storage mechanism • file backup service • data sharing • Data sync among different clients • Mobile applications Windows iPhone .mp3 .avi .jpg Linux iPad REST / JSON calls MAC Freemium business model Security (SSL, AES-256 bit), scalabity (load balancer, server notification, data/metadata..)
Example: iCloud from Apple cloud -contacts -photo -messages .. Phone backup -iCloud drive (store any kind of document)
Amazon’s Cognito https://aws.amazon.com/it/cognito/
Amazon’s Cognito • Amazon Cognito gives you unique identifiers for your end users and then lets you securely store and sync user app data in the AWS Cloud across multiple devices and OS platforms. • You can do this with just a few lines of code, and your app can work the same, regardless of whether a user’s devices are online or offline. • When new data is available in the sync store, a user’s devices can be alerted by a silent push notification so that your app can sync the new data automatically.
Characteristic of a cloud storage service • Bundling • When a batch of files is transferred, files could be bundled , so that transmission latency and control overhead are reduced. • For example, Dropbox use only few TCP connections to transfer multiple files • Chunking • Large files can be either monolithically transmitted to the cloud or chunked into smaller pieces. Chunking is advantageous because it simplifies recovery in case of failures • Dropbox 4MB, Google Drive 8MB,… • Compression • data compressed before a transfer. Compression could, in general, reduce traffic and storage requirements at the expense of local processing time.
Characteristic of a cloud storage service • Deduplication • Server data deduplication eliminates replicas on the storage server. • Client-side deduplication instead extends the benefits to clients and the network: In case a file is already present on servers, replicas in the client can be identified to save upload capacity • This can be accomplished by calculating a file digest using the file content, e.g., SHA256 is used by Dropbox • The digest is sent to servers prior to submitting the complete file. • Servers then check whether the digest is already stored in the system and skip the upload of repeated content. • Dropbox implements inter-user deduplication: this technique allows a user to skip submitting files that are already stored by any other user.
Characteristic of a cloud storage service • Delta encoding • Delta encoding calculates the difference among file revisions, allowing the transmission of only the modified portions. • Indeed, delta encoding provides similar benefits as the combination of chunking and deduplication, but with a finer granularity • P2P synchronization • Devices hosting common files could be synchronized without retrieving every content from the cloud, thus saving both network and server resources • Dropbox is known for implementing a LAN Sync Protocol that allows devices, possibly from different users, to exchange content using P2P communication when clients are connected to the same LAN.
Comparison among personal cloud storage(*) (*)E. Bocchi, I. Drago, M. Mellia, “Personal Cloud Storage Benchmarks and Comparison”, IEEE Transactions on Cloud Computing 2015
Other example: Microsoft’s Intune Microsoft Intune helps organizations provide their employees with access to corporate applications, data, and resources from virtually anywhere on almost any device, while helping to keep corporate information secure. Intune can manage: Mobile devices (including phones and tablets running Android, iOS, Windows Phone and Windows RT operating systems). Computers running a professional edition of Windows Vista, Windows 7, Windows 8 or Windows 8.1.
Cloud and mobile apps • Other ways to exploit cloud is by implementing a notification service
Google Cloud Messaging (GCM) GCM allows to attach up to 1,000 recipients to a single message connection server app server push -Broadcast ….. receiver
Amazon’s Simple Notification Service (SNS) • It is a fast, flexible, fully managed push notification service that lets you send individual messages or to fan-out messages to large numbers of recipients. • Amazon SNS makes it simple and cost effective to send push notifications to mobile device users, email recipients or even send messages to other distributed services.
Amazon’s SNS (features) • Seamlessly scale from a handful of messages per day to millions of messages or higher. • With SNS you can publish a message once, and deliver it one or more times. So you can choose to direct unique messages to individual Apple, Google or Amazon devices, or broadcast deliveries to many mobile devices with a single publish request. • SNS allows you to group multiple recipients using topics . • A topic is an “access point” for allowing recipients to dynamically subscribe for identical copies of the same notification. • When you publish once to a topic, SNS delivers appropriately formatted copies of your message to each subscriber.
Mobile apps and Software as a Service req reply Cloud -Cloud can play the role of ‘backend’ -provide access to resourses: • Functionality (VM, storage) using RPC-like calls) • Data (open data)
Example req reply Cloud real time data on transportation available from ATAC via XML-RPC http://www.agenziamobilita.roma.it/progetti/open-data/ http://www.agenziamobilita.roma.it/it/progetti/open-data/api-real-time.html
Mobile apps and web API (aka SaaS) A Web API allows to design and develop an application that exploits software Client modules accessed via Internet via a Application simple wire protocol INTERNET WEB-API
Web API: example
Web API: programmatic point of view Web URL (standard HTTP methods) web brower HTTP Rest,XML-RPC,etc HTTP (Web API) Application Programmatic Service Access (many methods)
Mashup applications s=A.methodName(par 1 ) … z=B.methodName(s,par 2 ) CLIENT Provide Provider API WEB … A B
Mashup applications (1/2) Client AJAX Python .. JSON-RPC … Web API … Web API Web API Server Server Server
Mashup applications (2/2) WEB API XML-RPC SOAP HTTP -Server Web -”mashupper” (e.g.,dynamic pages Php)
Web API and Interoperability Client Client Client Application Application Application (Technology A) (Technology B) (Technology C) WEB-API ….
Example: Google apis
Example: Tic Tac Toe • Monolithic application • All the logic is in a single program • Client Server • The server dynamically generates the page to be displayed with the response • Web API (cloud computing style) • Provides primitive operations to an application (that can run on a mobile device, for example) and let two players to play
solution1: monolithic app • Monolithic e.g., javaScript, or any language
Solution 2: client/server Put an X at position 7 http://game.org/ttt.php?move=7 HTML • Client HTTP Server + php
Possible technological mapping … (1/3) Client Server User Agent TCP/IP connection HTTP 3306,… HTML mod_php
…continued… (2/3) Client Server User Agent TCP/IP connection HTTP 3306,… HTML Embedded Objects mod_php
…continued(3/3) Client Server User Agent TCP/IP connection HTTP 3306,… HTML +JS mod_php
3 rd solution: Web Api and mobile app front end backend init Web API • Send the (cloud) current state move • Reply with the new state Interface (remote functions)
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