1. Enterprise Service Bus (ESB) (Chapter 9)
B. Ramamurthy
11/20/2018

2. 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
OMG’s CORBA (synchronous)
EJB in J2EE (synchronous)
IBM’s MQSeries (asynchronous)
Tibco’s Rendezvous (asynchronous)
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3. 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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4. 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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5. Service stub and dispatcher
op1
Service
stub
Service
dispatcher
op2
implementation
Client
API
op3 …
Op n
client
server
Stub and dispatcher are automatically generated
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6. 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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7. 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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8. Cross-container Integration
Service container
Access control service
Customer management service
Flight reservation service
Horizontal cross-container infrastructure
(security, transactions, logging)
System managing
& monitoring
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9. 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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10. Call Chain Airline Ticket service Ticketing Billing Reservation
Log file
Start billing
Finish billing
Start reservation
Finish reservation
Start ticketing
Finish ticketing
Airline Ticket
service
Ticketing
Billing
Reservation
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11. 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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12. 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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13. 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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14. 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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15. Other Security topics Firewalls (/proxies)
Encryption with various strengths
Secure socket layer (SSL)
Provisioning
Sarbanes-Oxley compliance
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16. Securing SOA ESB takes responsibility for securing an SOA
Trusted domains: airlines offering reservation on other airlines
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17. 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.
11/20/2018