Sistemas Distribuídos
Sincronização de Processos
Alex Borges Vieira
Objetivos
• Apresentar ao aluno os principais conceitos de sistemas
distribuídos e suas aplicações.
• Discutir problemas e técnicas relacionados à
implementação de sistemas distribuídos.
• Capacitar o aluno a implementar sistemas distribuídos
simples utilizando arquitetura cliente servidor e P2P.
• Apresentar aos alunos tendências e desafios na área de
sistemas distribuídos.
AVALIAÇÃO DE APRENDIZAGEM - CRONOGRAMA
Avaliação
Data
Valor
Tipo de Conteúdo Programático
Avaliaçã
o
TVC1
TVC2
TVC3
09/05
04/07
11/07
100
100
100
Prova
Prova
Trabalho
em grupo
Unidades de 1 a 5
Unidades de 6 a 10
Trabalho de caractere multidisciplinar
envolvendo todas as unidades da
disciplina (1 a 12).
Cálculo da Nota
Média: (4 * Primeira Nota + 4 * Segunda Nota + 2 * Terceira Nota)/10.
Aprovado se média maior/igual a 60.
Observações
a) PROVAS INDIVIDUAIS E SEM CONSULTA
b) Grupos compostos por 3 a 4 pessoas.
Cronograma para o Mês
1 Apresentação da disciplina
-objetivos e critérios de aprovação
Introdução aos Sistemas Distribuídos
-definição, Metas e Tipos
14/03/11
2
16/03/11
3 Arquiteturas de Sistemas Distribuídos (Estilos
Arquitetônicos, Arquiteturas de Sistemas, Arquiteturas
versus Middleware, Autogerenciamento)
21/03/11
4 Processos em Sistemas Distribuídos (Threads,
Virtualização, Clientes)
23/03/11
5
28/03/11
Processos em Sistemas Distribuídos (Servidores,
Migração de Código)
BIBLIOGRAFIA
Bibliografia Básica


COULOURIS, G.; DOLLIMORE, J.; KINDBERG, T. Distributed systems concepts and design. Third Edition, Addison-Wesley, 2001.
LYNCH, N. A. Distributed algorithms. Morgan Kauffmann, 1996.
Bibliografia Complementar





CHOW, R.; JOHSON, T. Distributed operating systems & algorithms. AddisonWesley, 1998.
GALLI, D. Distributed operating systems. Prentice-Hall. 2000.
HENNING, M.; VINOSKI, S. Advanced CORBA Programming with C++.
Addison-Wesley, 1998.
MULLENDER, S. (ed.). Distributed systems . Addison-Wesley, 1995.
TANENBAUM, A.S. Distributed operating systems. Prentice-Hall, 1995.
Idioma????
• Inglês!
– Livros mais novos
– Livros mais baratos
– Artigos de verdade
Characterization of
Distributed Systems
From Coulouris, Dollimore and Kindberg
Distributed Systems:
Concepts and Design
Edition 3, © Addison-Wesley 2001
Distributed Systems
• WTH is this?
Distributed Systems
• WTH is this?
Networking and Parallel Computing
• Computer networking
– Hardware that connects computers
– Software that sends/receives messages from one
computer to another, which might be on different
networks (end to end delivery)
– Goal is to transmit messages reliably and efficiently
• Parallel Computing
– Multiple homogeneous processors in “one” computer
– Shared or distributed memory
– Goal is to execute a program faster by division of
labor
Distributed Computing
• Networked computers that could be far apart
– rely on computer networking
• Communicate and coordinate by sending
messages
• Goal is to share (access/provide) distributed
resources
• Issues:
– Concurrent execution of processes
– No global clock for coordination
– More components, more independent failures
Examples of Distributed
Systems
• Global Internet
• Organizational Intranets--behind
router/firewall
• Mobile Computing -- computers move
• Ubiquitous Computing -- computers
embedded everywhere
• Issues:
– discovery of resources in different host
environments
– dynamic reconfiguration
Coulouris, Dollimore and
Kindberg Distributed Systems:
– limited connectivity
A typical portion of the Internet
intranet
%
ISP
%
%
%
backbone
satellite link
desktop computer:
server:
network link:
A typical intranet
email server
Desktop
c om pute rs
print and other servers
Loc al area
network
Web s erver
email server
File server
print
other s ervers
the res t of
the Internet
router/firewal l
Portable and handheld devices
in a distributed system
Internet
Hos t i ntranet
WAP
gateway
Wireless LAN
Mobile
phone
Printer
Laptop
Camera
Hos t s ite
Home intranet
Web servers and web browsers
www.google.com
http://www.google.comlsearch?q=kindberg
Browsers
Web servers
www.cdk3.net
Internet
http://www.cdk3.net/
www.w3c.org
File system of
www.w3c.org
http://www.w3c.org/Protocols/Activity.html
Protocols
Activity.html
Computers in the Internet
Date
1979, Dec.
1989, July
1999, July
Web servers
Computers
188
0
130,000
56,218,000
0
5,560,866
Computers vs. Web servers in
the Internet
Date
Computers
Web servers
Percentage
1993, July
1995, July
1997, July
1999, July
1,776,000
130
0.008
6,642,000
19,540,000
56,218,000
23,500
1,203,096
6,598,697
0.4
6
12
Computers vs. Web servers in
the Internet
Date
Computers
Web servers
Percentage
1993, July
1995, July
1997, July
1999, July
1,776,000
130
0.008
6,642,000
19,540,000
56,218,000
23,500
1,203,096
6,598,697
0.4
6
12
What happened with the
Internet in 2009?
• How many websites were added?
• How many emails were sent?
• How many Internet users were there?
Email
•
•
•
•
90 trillion – The number of emails sent on the Internet in 2009.
247 billion – Average number of email messages per day.
1.4 billion – The number of email users worldwide.
100 million – New email users since the year before.
•
•
•
•
81% – The percentage of emails that were spam.
92% – Peak spam levels late in the year.
24% – Increase in spam since last year.
200 billion – The number of spam emails per day
– assuming 81% are spam
Websites
• 234 million – The number of websites as of December 2009.
• 47 million – Added websites in 2009.
Websites
• 234 million – The number of websites as of December 2009.
• 47 million – Added websites in 2009.
Date
Computers
Web servers
Percentage
1993, July
1995, July
1997, July
1999, July
1,776,000
130
0.008
6,642,000
19,540,000
56,218,000
23,500
1,203,096
6,598,697
0.4
6
12
Domain Names
• 81.8 million – .COM domain names at the end of 2009.
• 12.3 million – .NET domain names at the end of 2009.
• 7.8 million – .ORG domain names at the end of 2009.
• 76.3 million – The number of country code top-level
domains (e.g. .CN, .UK, .DE, etc.).
• 187 million – The number of domain names across all toplevel domains (October 2009).
• 8% – The increase in domain names since the year before.
Internet Users
• 1.73 billion – Internet users worldwide (September 2009).
– 18% – Increase in Internet users since the previous year.
•
•
•
•
•
•
•
738,257,230
418,029,796
252,908,000
179,031,479
67,371,700
57,425,046
20,970,490
Internet users in Asia.
Internet users in Europe.
Internet users in North America.
Internet users in Latin America/Caribbean.
Internet users in Africa.
Internet users in the Middle East.
Internet users in Oceania / Australia.
Social Net.
• 126 million – The number of blogs on the Internet
– as tracked by BlogPulse
•
•
•
•
84% – Percent of social network sites with more women than men.
27.3 million – Number of tweets on Twitter per day
57% – Percentage of Twitter’s user base located in the USA
4.25 million – People following @aplusk
– Ashton Kutcher, Twitter’s most followed user
• 350 million – People on Facebook.
• 50% – Percentage of Facebook users that log in every day.
• 500,000 – The number of active Facebook applications.
Images
• 4 billion – Photos hosted by Flickr (October 2009).
• 2.5 billion – Photos uploaded each month to Facebook.
• 30 billion – At the current rate, the number of photos
uploaded to Facebook per year.
Videos
•
•
•
•
1 billion – videos YouTube serves in one day.
12.2 billion – Videos viewed per month on YouTube in the US
924 million – Videos viewed per month on Hulu in the US
182 – The number of online videos the average Internet user
watches in a month (USA).
• 82% – Percentage of Internet users that view videos online (USA).
• 39.4% – YouTube online video market share (USA).
• 81.9% – Percentage of embedded videos on blogs that are YouTube.
Malicious...
• 148,000 – New zombie computers created per day
– used in botnets for sending spam, etc.
• 2.6 million – Amount of malicious code threats at the
start of 2009
– viruses, trojans, etc.
• 921,143 – The number of new malicious code signatures
added by Symantec in Q4 2009.
Challenges and Issues (1)
• Heterogeneity
– networks, hardware, os, languages...
– middleware—corba
– mobile code, virtual machines
• Openness
– extended and re-implemented in various ways
– standard published interfaces
– RFC, request for comments
• Security
– confidentiality
– integrity
– availability
Challenges and Issues (2)
• Scalability
– effective with significant increase in resources
– cost
– performance
• Failure handling
–
–
–
–
–
detecting
masking—hide, less severe (retransmit)
tolerating--ignore, timeout
recovery--logs, rollback
Redundancy
• Concurrency
Transparencies
•Access transparency: enables local and remote
resources to be accessed using identical operations.
•Location transparency: enables resources to be
accessed without knowledge of their location.
•Concurrency transparency: enables several processes
to operate concurrently using shared resources without
interference between them.
Transparencies
•Replication transparency: enables multiple instances of
resources to be used to increase reliability and
performance without knowledge of the replicas by users
or application programmers.
•Failure transparency: enables the concealment of
faults, allowing users and application programs to
complete their tasks despite the failure of hardware or
software components.
•Mobility transparency: allows the movement of
resources and clients within a system without affecting
the operation of users or programs.
Transparencies
•Performance transparency: allows the system to be
reconfigured to improve performance as loads vary.
•Scaling transparency: allows the system and
applications to expand in scale without change to the
system structure or the application algorithms.