Enterprise Service Bus ESB Chapter 9

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Enterprise Service Bus (ESB)(Chapter 9)

• B. Ramamurthy

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The concept of bus

• Consider a hardware bus connects chips of
  different functions and from different vendors
• Now imagine a software bus a standardized way of
  hooking together any software components
  examples
• OMGs CORBA (synchronous)
• EJB in J2EE (synchronous)
• IBMs MQSeries (asynchronous)
• Tibcos Rendezvous (asynchronous)

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Types of ESB

• Ideal software bus supports a single
  communication model (fig.9.1).
• A software bus may also support various
  communication models at the same time (fig.9.2)
  synchronous, asynchronous, and file-based.
• The infrastructure of a real-world enterprise
  will normally consist of various products that
  support similar communication models.
• An enterprise is a meta bus that supports various
  products and technologies of the enterprise
• Example Credit Suisse uses a synchronous
  information bus, an asynchronous event bus
  infrastructure and a file transfer-based bulk
  integration infrastructure driven by application
  which in turn are driven by business demands.

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ESB Functions

• Stub/dispatcher code generation (development)
• Execution container functions (deployment)
• Logging and auditing (runtime management)
• An important item is missing in the text
  provisioning
• Availability and scalability
• Securing an SOA

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Service stub and dispatcher
op1
Service stub
Service dispatcher
op2
Client implementation
API
op3

Op n
client
server
Stub and dispatcher are automatically generated
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Execution containers

• Application servers
• Server farms
• Generic features set of an execution container
  are
• Dispatching and servicing
• Transaction management
• Security
• Logging
• Billing
• Systems management functionality
• Message transformation

Execution container
Resources queues, Data Sources, security details
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Cross-container integration

• Execution containers provide a rich set of
  functionality that makes deployment and
  management of individual services reasonably
  straightforward.
• However the key challenge of an enterprise SOA is
  to define an architecture that enables
  applications to use different services
  independently of their container.
• Challenges are interoperability including
  transactionality and security
• Solution in a system where services are
  implemented on incompatible execution containers,
  one must introduce a horizontal infrastructure
  layer that manages technical cross-container
  integration of services.

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Cross-container Integration
Service container
Access control service
Customer management service
Flight reservation service
Horizontal cross-container infrastructure (securit
y, transactions, logging)
System managing monitoring
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Logging and Auditing

• You must best practices to build robust systems.
• Even with such systems failures are unavoidable
• A error or failure must be reported to the user,
  to a log file or database and to a systems
  management system.
• Severity of the error is indicated by standard
  notations such as DEBUG, TRACE, INFO,
  WARN, ERROR, FATAL, and AUDIT
• Error reporting (SOAP error mechanism fault),
  distributed logging protocols (log locally, view
  globally)
• See Fig. 9-13

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Call Chain

• Log file
• Start billing
• Finish billing
• Start reservation
• Finish reservation
• Start ticketing
• Finish ticketing

Airline Ticket service
Ticketing
Billing
Reservation
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Availability and Scalability

• Scalability how well can you system perform
  under heavy load? What is the max load it can
  handle?
• Availability How is a failure of a system
  handled?
• Failstop
• Failover
• Degraded performance (low availability)

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Design Choices for scalability and availability

• Scalability and availability using WS
• Using enterprise java beans
• Using CICS
• Using CORBA
• Legacy applications
• Heterogeneous SOA beware of the weakest link for
  uptime

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Security Authentication

• Authentication means that a service caller is
  using a mechanism to prove its identity to the
  called resource.
• Individual login user name , password
• SOA level login Single sign on for all the
  requests in a session (fig 9-17)
• Authenticate yourself with an authentication
  service that provides tokens or tickets for
  interaction with subsequent interactions
• Security Assertion Markup Language (SAML)

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Security Authorization

• Authorization is the mechanism used to grant a
  caller access to a specific resource.
• Static group membership
• Role based access and dynamic group membership
• The concept of trust domain appropriate for SOA?
• Strict enforcement at application front-end once
  certified by this level, can freely access
  service at lower levels.

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Other Security topics

• Firewalls (/proxies)
• Encryption with various strengths
• Secure socket layer (SSL)
• Provisioning
• Sarbanes-Oxley compliance

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Securing SOA

• ESB takes responsibility for securing an SOA
• Trusted domains airlines offering reservation on
  other airlines

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ESB Summary

• ESB supports easy integration of the various SOA
  artifacts routing, messaging, invocation,
  mediation etc.
• ESB also provides the non-functional aspects such
  as security, availability, reliability,
  scalability, single sign-on etc.
• ESB is sold a software product by such as TIBCO.