6/4/2015Page 1 Enterprise Service Bus (ESB) B. Ramamurthy.
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6/4/2015Page 1 Enterprise Service Bus (ESB) B. Ramamurthy
6/4/2015Page 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)
6/4/2015Page 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.
6/4/2015Page 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
6/4/2015Page 5 Service stub and dispatcher Service stub API Client implementation Service dispatcher op1 Op n op3 op2 … clientserver Stub and dispatcher are automatically generated
6/4/2015Page 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
6/4/2015Page 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.
6/4/2015Page 8 Cross-container Integration Access control service Customer management service Flight reservation service Service container Horizontal cross-container infrastructure (security, transactions, logging) System managing & monitoring
6/4/2015Page 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
6/4/2015Page 10 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)
6/4/2015Page 11 Design Choices for scalability and availability Scalability and availability using WS Using enterprise java beans (see fig 8.15) Using CICS Using CORBA Legacy applications Heterogeneous SOA: beware of the weakest link for uptime
6/4/2015Page 12 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)
6/4/2015Page 13 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.
6/4/2015Page 14 Other Security topics Firewalls (/proxies) Encryption with various strengths Secure socket layer (SSL) Provisioning Sarbanes-Oxley compliance