cern it department ch-1211 genève 23 switzerland t brief introduction to messaging systems daniel...

CERN IT Department

CH-1211 Genève 23

Switzerlandwww.cern.ch/

it

Brief introduction to Messaging Systems

Daniel Rodrigues

CERN IT Department

CH-1211 Genève 23


it

InternetServices

Summary

CERN IT Department

CH-1211 Genève 23


it

InternetServices

Messaging Systems

• (Grid Maps image)

CERN IT Department

CH-1211 Genève 23


it

InternetServices

Messaging Systems

• What is Messaging?– Human communication process, characterized

for being asynchronous– Examples:

• The medieval messenger;• Post;• Message in a bottle.

• Abstraction of the communication process as messages being sent from one or more producers to one or more consumers;

Uhooo… that sounds complicated and off the scope :S

“Messaging is a technology that enables high-speed, asynchronous, program-to-program communication with reliable delivery. Programs communicate by sending packets of data called messages to each other. Channels (...) are logical pathways that connect the programs and convey messages. Senderor producer is a program that sends a message (...). A receiver or consumer is a program that receives a message (...)”

Hohpe et al, Enterprise Integration Patterns

CERN IT Department

CH-1211 Genève 23


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InternetServices

Messaging Systems

• Why use messaging?– For communicating we could use:

• File transfer• Shared Databases• Remote Procedure Calls• Web Services• Mail• CORBA

– They do exist;– They have common ideas;– They share implementations;– You might be using more than one to achieve a

result that suits your needs!

CERN IT Department

CH-1211 Genève 23


it

InternetServices

Messaging Systems

• Why use messaging?– Key ideas and benefits:

• Loosely coupled distributed communication;• Exceptional interoperability;• Asynchronous;• Reliable;• Configurable Persistence

– Drawbacks:• More complex programming model• Harder to do sequenced and synchronous model• Performance? (maybe FTP could do the trick)

CERN IT Department

CH-1211 Genève 23


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InternetServices

Messaging Systems

• How? (Or, “Ok, may we finally see a picture?”)

Publisher

Publisher

Publisher

Publisher

Consumer

• How?

CERN IT Department

CH-1211 Genève 23


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InternetServices

Messaging Systems

• Patterns: Message

– Header • Routing information• Description

– Body • Data• Ignored by the messaging system

– EventMessage, CommandMessage, DocumentMessage, RequestReply

– Could be SOAP, JMS, Stomp, etc.

CERN IT Department

CH-1211 Genève 23


it

InternetServices

Messaging Systems

• Patterns: Message Channel

– Point-to-Point• Snail Mail• Queues

– Publish-Subscribe• Television/radio Broadcast• Topics

– DataTypeChannel, InvalidMessageChannel, DeadLetterChannel, ChannelAdapter, MessageBus, MessagingBridge

CERN IT Department

CH-1211 Genève 23


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InternetServices

Messaging Systems

• Patterns: Message Endpoint

– Publisher • Gets data from application and creates a message.

– Consumer• Extracts data from a message and passes it on to the application.

– SelectiveConsumer, CompetingConsumer, DurableSubscriber, MessageDispatcher, TransactionalClients, EventDrivenConsumer.

– Endpoints either sends or receives messages, and are channel specific. (Ears mouth,eyes are not the same thing)

CERN IT Department

CH-1211 Genève 23


it

InternetServices

Messaging Systems

• Isn’t it too complex to implement all this?– Indeed.

• But someone has already done most of the work for you:– Commercial solutions:

• Tibco Rendezvous, IBM WebSphere MQ, SUN Java Message Service, Microsoft MSMQ, BEA MessageQ, SonicMQ, 29West UME/LBM.

– OpenSource providers:• Apache ActiveMQ, ObjectWeb JORAM, Open JMS.

• Each are adequate to different problems.– Integration on different platforms;– Latency concerns;– High throughputs;

CERN IT Department

CH-1211 Genève 23


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InternetServices

Messaging Systems

• Where is it used? – Financial Services

• exchanges, brokerages, hedge funds;– Insurance Companies– Banking Industry– Telecoms

• Usually embedded in integrated solutions– Enterprise Backbones;

• WebsphereMQ example (March 2007):– 10.000 customers– 10 billion messages carrying US$1 quadrillion (US$ 1 000 000 000 000 000) worth of business

transactions.

CERN IT Department

CH-1211 Genève 23


it

InternetServices

Messaging Systems

• Where is it used? – MSG! Messaging System for the Grid;

• Used in Monitoring;• Based on an ActiveMQ backbone and python;• Simple way to send records across…• …and have multiple consumers consuming into an

Oracle DB;

• SAM: metricOutput, metricDescriptions;• GridFTP transfers : Gridview;• Job Status, Job Details from various sources.

CERN IT Department

CH-1211 Genève 23


it

InternetServices

Messaging Systems

• And now, for something completely different

CERN IT Department

CH-1211 Genève 23


it

InternetServices

Messaging Systems

• Other Patterns– Message Routers

• Message may be routed to different channels depending on its characteristics;

• Simple Example: use a wild card topic! – grid.usage.transfer.*, where it will be forwarded to

grid.usage.transfer.<INFRASTRUCTURE>

– MessageTranslators• Translation at different layers (data structure, types,

representation, or transport).• e.g. transport protocols: TCP => HTTP => SOAP => JMS

– Pipes and Filters• Message may need processing in different steps.• A Message goes through filtering and pipes that perform

different functions (e.g, authN, authZ)

CERN IT Department

CH-1211 Genève 23


it

InternetServices

Messaging Systems

• And now, for something completely different

cern it department ch-1211 genève 23 switzerland t brief introduction to messaging systems daniel...

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