Brief introduction to Messaging Systems

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Brief introduction to Messaging Systems

• Daniel Rodrigues

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Summary

• Messaging Systems Overview
• What
• Why
• How
• Where
• Monitoring context in the Grid
• The MSG Messaging System for Grids
• Fast Forward

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Messaging Systems

• (Grid Maps image)

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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. Sender or 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
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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!

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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)

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Messaging Systems

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

• How?

Publisher
Publisher
Publisher
Publisher
Consumer
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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.

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Messaging Systems

• Patterns Message Channel
• Point-to-Point
• Snail Mail
• Queues
• Publish-Subscribe
• Television/radio Broadcast
• Topics
• DataTypeChannel, InvalidMessageChannel,
  DeadLetterChannel, ChannelAdapter, MessageBus,
  MessagingBridge

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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)

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Messaging Systems

• Isnt 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

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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 US1 quadrillion
• (US 1 000 000 000 000 000) worth of business
  transactions.

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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.

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Messaging Systems

• And now, for something completely different

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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.ltINFRASTRUCTUREgt
• MessageTranslators
• Translation at different layers (data structure,
  types, representation, or transport).
• e.g. transport protocols TCP gt HTTP gt SOAP gt
  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)

16
Messaging Systems

• And now, for something completely different

17
Messaging Systems

• And now, for something completely different

18
Messaging Systems

• And now, for something completely different