Cloud Computing 014 - uniroma1.it · Cloud computing • Cloud computing, like other technologies,...

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Introduction to Cloud Computing

Roberto Beraldi

CC in a nutshell

• Cloud computing is a way to use Information

Technology infrastructures without the need to

install specific HW related to the infrastructures

being used.

• IT infrastructure can be as simple as a single raw

virtual machine, …

… more abstract as a sw platform used to develop

and running applications on several machines,

…or a sw application

Cloud computing in a nutshell

(by an analogy)

• Electricity is “virtual” entity – (many sources, we do not care from where we receive it,…)

• “Pay-as-you-go” – Elastic

Production Distribution Utilization

CC: Virtual computing power

cycles

Storage

Memory

Provider Utilization

Virtual machine

control panel

User decides the size on the VM…

Cloud computing

• Cloud computing, like other technologies, such as cluster, grid, aims at allowing access to large amounts of computing power in a fully virtualized manner, by aggregating resources and offering a single system view.

• Cloud computing has been coined as an umbrella term to describe a category of sophisticated on-demand computing services initially offered by commercial providers, such as Amazon, Google, and Microsoft.

What CC can provide?

• Infrastructure

• Platform

• Software

• API

• STorage

• Desktop

as a service (IaaS)

as a service (PaaS)

as a service (SaaS)

as a service (APIaaS)

as a service (STaaS)

as a service (DaaS)

as a service (XaaS)

Main characteristics of CC

• Pay-per-use

– no ongoing commitment, utility prices;

• Elastic capacity and the illusion of infinite resources;

• Resources that are abstracted or virtualized.

• Resources provided as a Service and with a self-service Interface

– provides users the ability to upload, build, deploy, schedule, manage, and report on their business services on demand.

Factors enabling cloud computingHardware

HW virtualization

Multi-core chipsIn

Distrib

Web 2.0

Web Services

Mashups

Utility computing

Grid Computing

System Management

Autonomic Computing

Data Center Automation

computing

Cloud actors

From mainframes to clouds

• Providers of CC can operate their

infrastructures at very high utilization rate

• Something similar to what happened with

Mainframes.

– They had to operate at very high utilization rates

simply because they were very expensive and

costs should be justified by efficient usage

Provisioning

Provisioning for peak load

Underprovisioning, case 1

Underprovisioning case 2

Types of Cloud Computing

(IaaS) Infrastructure as a Service

(SaaS)Software as a Service

XaaS (PaaS) Platform as a Service

INFRASTRUCTURE AS A SERVICE

• A cloud infrastructure enables on-demand provisioning of servers running several choices of operating systems and a customized software stack.

• Cloud computing services are usually backed by large-scale data centers composed of thousands of computers.

• Such data centers are built to serve many users and host many disparate applications.

• Offers virtualized resources (computation, storage, and communication) on demand

Virtualization - isolation

• Through virtualization, workload isolation is achieved since all program instructions are fully confined inside a VM, which leads to improvements in security.

• Better reliability is also achieved because software failures inside one VM do not affect others.

• Moreover, better performance control is attained since execution of one VM should not affect the performance of another VM.

Virtualization - isolation

Virtualization – application mobility

• Workload migration, also referred to as application mobility, targets at facilitating hardware maintenance, load balancing, fault tolerance and disaster recovery.

• It is done by encapsulating a guest OS state within a VM and allowing it to be suspended, fully serialized, migrated to a different platform, and resumedimmediately or preserved to be restored at a later date.

• A VM’s state includes a full disk or partition image, configuration files, and an image of its RAM.

Virtualization – application mobility

Virtualization - consolidation

• Virtualization makes it possible to consolidate

individual workloads onto a single physical

platform, reducing the total cost of ownership.

Virtual machines

• Virtual machine is a logic machine implemented via

software (ML) running on a physical machine (MF)

• Two main types

• No native emulation ML≠MF

• Native emulation. ML=MF

Process virtual machine

• Runs a SW process

• Examples Java Virtual Machine

• Common Language Runtime (CLR)/.NET

Virtual machine and interoperabiity

• Java Virtual Machine (JVM)

– ISA: Macchina a stack (zero-register)

MF1 MF2 MFn

• “write once run

everywhere”

System virtual machine

• Same machine as the physical machine

“Efficient, isolated duplicate of a real

machine”*)

• Virtualization is realized by a Virtual Machine

Monitor (VMM) o hypervisor

• Process : SO = Supervisor : Hypervisor

System virtual machine

• Full virtualization

– OS without modification (VMWare)

– OS legacy

• Paravirtualization

– OS must be modified

– Higher effciency

Resources

• Xen and the Art of Virtualization, Pratt et al. SOSP

• The Architecture of Virtual Machines, Smith, J.E.; R.

Nair, IEEE Computer, May 2005, Volume: 38 , Issue: 5

• A Comparison of Software and Hardware Techniques

for x86 Virtualization, K. Adams, O. Agesen. ASPLOS

Classical virtualization

• “A classical VMM executes guest operating system directly, but at a reduced privilegedlevel. The VMM intercepts traps from the de-privileged guest, and emulates the trapping instruction against a virtual machine state”[*]

[*]”A camparison of Software and Hardware Techniques for x86 Virtualization”, K.Adams, O.Agesen, ASPLOS 2006

Classical virtualization, esempio

Guest OS Istruzione non privilegiata

verde = User Mode

rosso = System Mode

Istruzione privilegiata

p.e. CLI, Clear Interrupts

Livello User Livello Kernela. CPU executes a kernel

instruction of the Guest OS

while being in user mode

b. CPU generates a trap

c. Control passes to the VMM

that emulates the instruction

d. 2’ is different of 2, but is

produces the same effect (

(for example,

CLI�VCPU.IF=0)

Hw virtualizazion

Hardware virtualization allows running multiple operating systems and software

stacks on a single physical platform.

The virtual machine monitor (VMM), also called a hypervisor, mediates access to the

physical hardware presenting to each guest operating system a virtual machine

(VM), which is a set of virtual platform interfaces

Type-1 hypervisor (bare metal)

• Guest OS runs unchanged

• Used to build a “Hardware Server” (cloud computing)

• Hyper-V(Microsoft) , VMWare ESX

Type-2 hypervisor (hosted)

• Runs on top of a Hosting OS

• Guest OS unchanged (full virtualization)

• Often used on clients

Example of VMM: Virtual Box

• It usually runs on Desktop computers

• VMM runs as an application hosted by an OS

• Software-based virtualization

• Lower performance, easy to install VM (demo)

IaaS provider’s point of view

• A key challenge IaaS providers face when

building a cloud infrastructure is managing

physical and virtual resources, namely servers,

storage, and networks, in a holistic fashion.

• The orchestration of resources must be

performed in a way to rapidly and dynamically

provision resources to applications.

IaaS provider’s point of view

• The software toolkit responsible for this orchestration is called a virtual infrastructure

manager (VIM).

• This type of software resembles a traditional operating system (“cloud operating system”)—but instead of dealing with a single computer, it aggregates resources from multiple computers, presenting a uniform view to user and applications.

Example: OpenNebula

• Interface to Public Clouds: it offers a driver to

manage the life cycle of virtualized resources

obtained from external cloud providers.

• In case of spikes in demand, extra load can be

offloaded to rented resources. To the

applications, the use of leased resources must

ideally be transparent

IaaS: deployment model

Example of IaaS

• Windows azure

• Different machine with different size and OS

• Different geographical region where the

machine is located

• Free trial (requires registration with VISA)

Platform as a Service

• A cloud platform offering an environment on which developers create and deploy applications

• Developers do have access to a SDK that allows to develop a new application and to deploy it in the cloud

• Impact on the programming model

• Google’s app engine, Windows Azure, and many more…

PaaS – example: GAE

• Cloud service for running web applications on the

Google data center

• Do one thing well

– Simple configuration

– Transparent scalability

• “infinite” number of applications, req/sec storage

– Security

• All applications run inside a sandbox, do not have direct access to

file system, cannot open other connections

GAE architecture

• Google App Engine speaks with web applications through the Web Server Gateway Interface (WSGI) standard protocol

• App Engine and SDK includes the webapp2 framework that implements WSGI

– Advanced frameworks can be used, e.g., Django

WEB AppHTTP Requests

WEB Server

WSGI Protocol

GAE: supported language

• Java

– JVM, Java servlet, …

– SDK Eclipse extension

• Python

– Standard library (without ‘unsecure’ calls)

• Go

LAB: Hello Word in GAE

• What we need:

– Google account

– GAE registration

• Plafond free (10 app)

– Register a new application

• The application ID will be used to deploy the

application

– SDK

– Python 2.7 (no support for 3.x)

Hello Word in GAE

helloworld.py

app.yaml

ConfSimulator

“Google Cloud”Deploy

Web-based Admin console

Step 1

Step 3

Step 2

Step 4

Hello Word in GAE

• Define a handler for the HTTP requests as a class that extends webapp2.RequestHandler class (MainPage)– Attributes : response, request (instance of class Request, Response)

– Methods: get,post, etc.. (to override)

• Map HTTP get request to get method (also post, put, etc..)

• Write data to HTTP response through self.response

• app is a global name that must assigned to the application

helloworld.py

Step 1

app.yaml

“Google Cloud”Deploy

Web-based Admin console

Step 3

Step 4

• An application name helloword must be registered with the google engine– helloworld.appspot.com

appcfg.py update .

GAE architecture (simplified view)

App Eng

Front End

App Eng

Front End

App Eng

Front End

App Server

App Server App Server

API layer

APP APP APP

Google

Service

HTTP Requests

Python GAE architecture

Python

Standard

Read-only

File system

Source: Google App Engine – Guido van Rossum

REQ/REP

DATASTOREMEMCACHE

BigTable

URLfetch

images

ServicesSandbox

Python GAE architecture (scaling)

Python

Standard

Read-only

File system

Source: Google App Engine – Guido van Rossum

REQ/REP

DATASTOREMEMCACHE

BigTable

URLfetch

images

ServicesSandbox

PaaS example2: Windows Azure

• It is a set of integrated cloud technologies each

providing a specific set of services to application

developers

• Windows Azure provides developer-accessible

services for creating applications

• Strongly integrated with Visual studio

– Development fabric simulator

– Development storage simulator

Windows azure

• Two execution models for applications – Web hosting: Web Site

– PaaS: Cloud Service

• IaaS: Virtual Machines

http://www.windowsazure.com/en-us/develop/net/fundamentals/intro-to-windows-azure/

DeployementWeb Portal

1. Register (Live-id)

Conf(n.inst. =3)

Fabric

Controller

Service

.cspkg

Service

2. Create Hosted-Service

http://xxxx.cloudapp.net

3. Package upload

.csconf + .cspkg

SOFTWARE AS A SERVICE

Types of Cloud Computing

(IaaS) Infrastructure as a Service

(SaaS)Software as a Service

XaaS (PaaS) Platform as a Service

Access to Cloud computing

• A service is delivered through two access points:

• Standard web browsing (HTTP) and

• Programmatic access (Rest,XML-RPC,SOAP, etc. over HTTP)

Programmatic Service Access

(many methods)

Web URL

(standard HTTP methods)

web browerHTTP

Application

Rest,XML-RPC,etc

Service

What is a service?

SERVICE

--------

Interface definition (e.g., WSDL)

Technology A

Technology B

Technology C

Web API (aka API as a Service)

• Delivering basic building blocks as ‘services’

for other programs

• Services can be offered via simpler protocols

– JSON, JSON-RPC, REST, JSONP,…

Web API (aka API as a Service)

Web-API

• Based of RPC/HTTP

• Two main data representations

– JSON

– XML

• Protocols

– XML-RPC

– JSON-RPC

– SOAP

– REST

Web API: RPC over Internet• RPC calls mapped onto HTTP (GET or POST)

• Synchronous call

• Asynchronous call– with callbacks

• External data representation– JSON (Java Simple Object Notation)

• http://www.json.org/json-it.html

– XML

• Protocols– REST, SOAP, JSONP, JSON-RPC, XML-RPC,…

• Two fundamental structures:

See JSON Lint

XML in a nutshell

• XML (eXtensible Markup Language) is a language derived fromSGML (Standard Generalized Markup Language), from whichHTML also derives.

• The key notion in the markup language familty is a markup,something that describes some aspect of the data

• In HTML markups define the appearance of the document,whereas in XML they define the meaning of the data

XML in a nutshell

• An XML document is a tree

• Data appear inside elements

• An element not only contains the data itself but alsoinformation describing the meaning of the data

Example

Il Signore degli Anelli, di John Ronald Reuel Tolkien,

Bompiani.

Author

Editor

Example

<book>

<title>

Il Signore degli Anelli

</title>

John R. R. Tolkien

</author>

Bompiani

</editor>

</book>

Author

Editor

Book Elements

Tips : Browser allows to see the structure of the document

Elements and attribute

<title>

</title>

</title>

Attribute (key/value pair)

Well formed document

Valid document

• Document that follows composition rules

about the its structure

• Two solutions

• Document Type Definition

– Easier, less ‘powerfull’

• XML Schema

– More complex, more powerfull

WFD and validation

DocumentSyntax check

Semantic

checkGrammar

XML-RPC

Overview of XML-RPC

• Data Model

– Scalar

– Struct

– Array

• Messages

– Request message

– Response message

– Error message

Scalar types

Tag Type Example

<i4> or <int> four-byte signed integer -12

<boolean> 0 (false) or 1 (true) 1

<string> string hello world

<double> double-precision signed floating point

number

-12.214

<dateTime.iso8601> date/time 20101504T09:30:00

<base64> base64-encoded binary eW91IGNhbid0IHJlYWQgdGhpcyE=

Struct type

<name>lowerBound</name>

</member>

<name>upperBound</name>

</member>

</struct>

Array type

<array>

<data>

<value><string>Egypt</string></value>

</data>

</array>

Request message

• Root element: methodCall

• contains a MethodName element and a params

element

• MethodName contains the name of the procedure

being called

• Params is a list of values for the parameters

Example

<?xml version="1.0"?>

<param>

</param>

<param>

</param>

</params>

</methodCall>

Example<?xml version="1.0"?>

<param>

</param>

<param>

</param>

</params>

</methodCall>

methodCall

methodName

params

param valuei4

param valuedouble

Example<?xml version="1.0"?>

<methodName>Scuola XXX</methodName>

<param>

</param>

<param>

</param>

</params>

</methodCall>

methodCall

methodName

params

param valuei4

param valuedouble

methodName

params

paramparam

doublei4

methodCall

Complete request message

POST /xmlrpc HTTP 1.0

User-Agent: …

Host: …

Content-type: text/xml

Content-length: ..

<?xml version=“1.0”?>

<methodName>Circle_Area</methodName>

</methodCall>

Reply message

<?xml version="1.0"?>

<param>

</param>

</params>

</methodResponse>

Fault message<?xml version="1.0"?>

<fault>

<value>

<name>faultCode</name>

</member>

<name>faultString</name>

<value><string>Too many parameters.</string></value>

</member>

</struct>

</value>

</fault>

</methodResponse>

JSON-RPC 2.0

• JSON-RPC is a stateless, transport agnostic,

light-weight remote procedure call (RPC)

protocol

• Much like XML-RPC

– No formal grammar

– Definition of request object and reply object

• New feature: batch requests, notification

Some example

--> {"jsonrpc": "2.0", "method": "subtract", "params": [42, 23], "id": 1}

<-- {"jsonrpc": "2.0", "result": 19, "id": 1}

-->{"jsonrpc": "2.0", "method": "subtract", "params": [23, 42], "id": 2}

<-- {"jsonrpc": "2.0", "result": -19, "id": 2}

-->{"jsonrpc": "2.0", "method": "subtract", "params": {"subtrahend": 23, "minuend": 42}, "id": 3}

--> {"jsonrpc": "2.0", "method": "subtract", "params": {"minuend": 42, "subtrahend": 23}, "id": 4}

JSON-RPC call batch

--> [{"jsonrpc": "2.0", "method": "sum", "params": [1,2,4], "id": "1"},{"jsonrpc": "2.0", "method": "notify_hello", "params": [7]},{"jsonrpc": "2.0", "method": "subtract", "params": [42,23], "id": "2"},{"foo": "boo"},{"jsonrpc": "2.0", "method": "foo.get", "params": {"name": "myself"}, "id": "5"},{"jsonrpc": "2.0", "method": "get_data", "id": "9"} ]<-- [{"jsonrpc": "2.0", "result": 7, "id": "1"},{"jsonrpc": "2.0", "result": 19, "id": "2"},{"jsonrpc": "2.0", "error": {"code": -32600, "message": "Invalid Request."}, "id": null},{"jsonrpc": "2.0", "error": {"code": -32601, "message": "Method notfound."}, "id": "5"},{"jsonrpc": "2.0", "result": ["hello", 5], "id": "9"}]

JSONP (JSON with Padding)

f(JSON data)

Used in JavaScript

Allows to overcome the cross-

domain problem

Uses a callback function

• Method calls are mapped to HTTP request

(Get, Post)

• Method name is a parameter of the call

• Reply is usually formatted as JSON or XML

• It’s by far the most verbose protocol

• Service is described in WSDL file

• Messages as XML documents formatted

according to a specific schema

Tool utili per il debugging

RPC over Internet: example

http://api.wunderground.com/api/http://api.wunderground.com/api/http://api.wunderground.com/api/http://api.wunderground.com/api/KEYKEYKEYKEY////FEATUREFEATUREFEATUREFEATURE/[/[/[/[FEATUREFEATUREFEATUREFEATURE…]/q/…]/q/…]/q/…]/q/QUERYQUERYQUERYQUERY....FORMATFORMATFORMATFORMAT

Features

geolookupconditions forecast

types= JSON, XML

Example

http://api.wunderground.com/api/[API_KEY]/conditions/q/rome.json

location ID

http://api.wunderground.com/api/[API_KEY]/conditions/q/rome.json?callback=f

Example of XML reply

http://api.wunderground.com/api/[APIKEY]/conditions/q/zmw:00000.1.16240.xml

Interoperability

Chrome Developer tool

Static call

• Using JS src you can “make a call” and display

results on the screen

Static call

Dynamic Call

Dynamic call

1. Dynamically create a HTML element and append in

the head section

2. Call the URL with callback function

Dynamic call

• Show the current temperature on the screen

Using jQuery

Additional example

Example: Geocoding API

Example: Geocoding API (json)

Example: Geocoding API (xml)

Example: reverse Geocoding (json)

Example: Reverse geocoding (xml)

Google’s JavaScript API (vers. 3)

Example

Example:

Geolocation in HTML5

Example: Flickr ®

Flickr: request, reply message format

http://api.flickr.com/services/xmlrpc/

http://api.flickr.com/services/soap/

WEB-API

http://api.flickr.com/services/rest/

Example: rest call

Example

• Reply is wrapped through jsonFlickrApi

callback name

• To avoid this, set nojsoncallback=1 option

json format

Asynchronous RPC: AJAX

Sicurezza:

Cross domain non è

consentito

Example: using AJAX

Example: searching photos

Example: searching data

Key photo contains photo details

Example: searching photo

Every photo has a link

[mstzb] defines the size

Example: searching photos

Other example

http://api.wordreference.com/{api_version}/{API_key}/{dictionary}/{term}

http://api.wordreference.com/{api_version}/{API_key}/JSON/{dictionary}/{term}

Example

Example: Twitter API

Exercise

• Write a simple JS program for the TTT game

• Hint:

– use a table for button formatting

– Use a single handler to make modification

Other web API

• http://openweathermap.org/api

• EditGrid

• Dropbox is a free (up to 2GB), web-based cloud storage mechanism– file backup service

– data sharing

– Data sync among different clients

– Mobile applications

Android

iPhone

Blackberry

Windows

.avi.jpg

REST / JSON

STorage as a Service

Questions?

Cloud Computing 014 - uniroma1.it · Cloud computing • Cloud computing, like other technologies,...

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