EEC-681/781 Distributed Computing Systems

EEC-681/781EEC-681/781Distributed Computing Distributed Computing

SystemsSystems

Lecture 6Lecture 6

Wenbing ZhaoWenbing ZhaoDepartment of Electrical and Computer EngineeringDepartment of Electrical and Computer Engineering

Cleveland State UniversityCleveland State University

[email protected]@ieee.org

Fall Semester 2006Fall Semester 2006 EEC-681: Distributed Computing SystemsEEC-681: Distributed Computing Systems Wenbing ZhaoWenbing Zhao

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Message-Oriented CommunicationMessage-Oriented Communication

• Persistence and Synchronicity in Communication• Message-oriented transient communication

– Berkeley sockets– Message-passing interface

• Message-oriented persistent communication– Message-queuing system– Message brokers (publish/subscribe)

• Java message service– A copy of JMS tutorial is available at DCS server

/software/activemq/jms-tutorial.pdf


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Synchronous CommunicationSynchronous Communication

• Client/Server computing is generally based on a model of synchronous communication:– Client and server have to be active at the time of

communication– Client issues request and blocks until it receives

reply– Server essentially waits only for incoming

requests, and subsequently processes them


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Synchronous CommunicationSynchronous Communication

• Drawbacks of synchronous communication:– Client cannot do any other work while waiting

for reply– Failures have to be dealt with immediately (the

client is waiting)– In many cases the model is simply not

appropriate (mail, news)


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Asynchronous CommunicationAsynchronous Communication

• Message-oriented middleware: Aims at high-level asynchronous communication:– Processes send each other messages, which

are queued– Sender need not wait for immediate reply, but

can do other things– Middleware often facilitates fault tolerance


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Persistent CommunicationPersistent Communication• Persistent Communication – A message that

has been submitted for transmission is stored by the communication system as long as it takes to deliver it to the receiver– E.g. from postal mail to e-mail


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Transient CommunicationTransient Communication

• Transient Communication – A message is stored by the communication system only as long as the sending and receiving application are executing– All transport-level communication services

offer only transient communication– RPC/RMI


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Message-Oriented Message-Oriented Transient CommunicationTransient Communication

• Berkeley Sockets

• Message-Passing Interface


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Berkeley SocketsBerkeley Sockets

Primitive Meaning

Socket Create a new communication endpoint

Bind Attach a local address to a socket

Listen Announce willingness to accept connections

Accept Block caller until a connection request arrives

Connect Actively attempt to establish a connection

Send Send some data over the connection

Receive Receive some data over the connection

Close Release the connection


1010

Berkeley SocketsBerkeley Sockets

Connection-oriented communication pattern using sockets


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The Message-Passing Interface (MPI)The Message-Passing Interface (MPI)

• MPI is used to do high performance computing on multicomputers – Use high-speed interconnection networks– Come with proprietary communication

libraries

• Need message-passing primitives at a convenient level of abstraction– Standard APIs, hardware-independent


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Message-Oriented Message-Oriented Persistent CommunicationPersistent Communication

Message-Oriented

Middleware

Application A

Messaging API

Messaging Clients

Application B

Messaging API

Messaging Clients

Message-Oriented Middleware (MOM)


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Characteristics of MOMCharacteristics of MOM

• Loosely-coupled communication: They offer intermediate storage capacity for messages, without requiring either sender or receiver to be active during message transmission

• Encompasses publish/subscribe and message queuing communications

Sender Receiver

MOM

Messages


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Message QueuingMessage Queuing

Producer Queue Consumer

send(m1)

send(m2)

receive()m1

Put message into queue

Consume message

A message queue offers point-to-point communication: each message produced has one consumer


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Publish/SubscribePublish/Subscribe

Producer Broker Consumer Consumer

publish(m1)send(m1)Pass message to

brokersend(m1)

send(m2)

send(m2)

Dispatch message to all consumers

publish(m2)

publish(m3)

Publish/subscribe offers one-to-many communication: each message published can have many subscribers


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Message Queuing ApplicationMessage Queuing Application


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Publish/Subscribe ApplicationPublish/Subscribe Application

subscribe (“EEC681”);subscribe (“EEC681”);subscribe (“EEC693”);

subscribe (“EEC681”);subscribe (“EEC693”);

publish(“EEC681”, Lab1);publish(“EEC681”, Lab2);

publish(“EEC693”, HW1);publish(“EEC693”, HW2);


1818General Architecture of General Architecture of Message-Queuing SystemMessage-Queuing System

• Message queueing API provides a higher abstraction to application developers

• Queue-level addressing is translated to transport-level addressing in MOM


1919General Architecture of General Architecture of Message-Queuing SystemMessage-Queuing System

• A message can be handled by a centralized message server, or routed by multiple queue managers– Scalability– Secondary

processing of messages, e.g., logging, bridging


2020

Java Message ServiceJava Message Service

• Standard Java API

• Message delivery models

• Two messaging models

• Transactions

• Reliability levels

• Persistent messaging


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JMS Messaging DomainsJMS Messaging Domains

• Publish and subscribe (topic)– Many consumers per message

• Point-to-point (queue)– One consumer per message


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JMS ComponentsJMS Components

Message Server

Message MessageDestination

JMS Client

Connection

Session

Producer

JMS Client

Connection

Session

Consumer


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Connections and SessionsConnections and Sessions

• A connection connects to a message server

• You can create one or more sessions within a connection

JMS Client

Connection

Session

Session

Session


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Creating Connections and Creating Connections and SessionsSessions

Message Server

JNDI Store

JMS Client

Connection

Session

Session

Session

ConnectionFactory

create

ConnectionFactoriesDestinations


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JMS Message TypesJMS Message Types

Message type Message body

Message No body

TextMessage A standard Java string

ObjectMessage A serializable Java object

MapMessageA set of name/value pairs where values are Java primitives

StreamMessage A stream of Java primitives

BytesMessage A stream of uninterpreted bytes


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Creating a MessageCreating a Message

createStreamMessage( )

StreamMessage

TopicSession

createTextMessage( )

TextMessage

QueueSession


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JMS Message HeadersJMS Message Headers

• Automatically assigned headers– JMSDestination– JMSDeliveryMode– JMSMessageID– JMSTimestamp– JMSExpiration– JMSRedelivered– JMSPriority

• Developer-assigned headers– JMSReplyTo– JMSCorrelationID– JMSType


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Producers, Consumers, and Producers, Consumers, and DestinationsDestinations

Message ServerSend

messageConsumemessage

Destination

Producer

Bind todestination

Consumer

Read message

Bind todestination


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Creating DestinationsCreating Destinations

Message Server

JNDI StoreJMS Client

Topic

Queue

ConnectionFactoriesDestinations lookup


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Producing a MessageProducing a Message

create message

produce message

Session

MessageProducer

Message Destinationcreate


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Consuming MessagesConsuming MessagesIncoming messages

MessageListener

onMessage(message)

Message Server

acknowledge

MessageConsumer

Message receive()

Incoming messages

acknowledge

Asynchronous Message Delivery

Synchronous Message Delivery


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Filtering with Message SelectorFiltering with Message Selector

Message Server

Publisher

Departments.Sales

SubscriberDepartments.SalesPipeline > 15000

JMSPriority = 2Pipeline = 20000

delivered

SubscriberDepartments.SalesJMSPriority > 5

not delivered

SubscriberDepartments.SalesJMSPriority >= 2 AND Pipeline > 10000

delivered

SubscriberDepartments.SalesPipeline > 20000

notdelivered


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Browsing a QueueBrowsing a Queue

nextElement()

QueueBrowser

getEnumeration()

Message1

Message2

Message3

Message4

Enumeration


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Accessing Message ContentAccessing Message Content

Message

TextMessageMapMessage ObjectMessage StreamMessage BytesMessage

getText() getObject()

get<type>(Name)

read<type>()

Documents

EEC-681/781 Distributed Computing Systems