Concepts and Architecture

Overview

BEA AquaLogic Service Bus—part of BEA's new family of Service Infrastructure Products (AquaLogic)—combines intelligent message brokering with service monitoring and administration to provide a unified software product for implementing and deploying your Service-Oriented Architecture (SOA). This converged approach adds a scalable, dynamic routing and transformation layer to your enterprise infrastructure, plus service lifecycle management capabilities for service registration, service usage, and Service Level Agreement (SLA) enforcement.

AquaLogic Service Bus is a configuration-based, policy-driven Enterprise Service Bus (ESB). It provides a feature-rich console for dynamic service and policy configuration, as well as for system monitoring and operations tasks. The AquaLogic Service Bus Console enables you to respond rapidly and effectively to changes in your service-oriented environment.

AquaLogic Service Bus relies on WebLogic Server run-time facilities. It leverages WebLogic Server capabilities to deliver functionality that is highly available, scalable, and reliable.

This topic introduces AquaLogic Service Bus. It is intended for enterprise architects, operations specialists, and security architects who are responsible for messaging and SOA. It includes the following sections:

• Introducing AquaLogic Service Bus
• AquaLogic Service Bus Core Feature Set
• AquaLogic Service Bus Message Brokering
• AquaLogic Service Bus Architecture

 

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Introducing AquaLogic Service Bus

Enterprise architects responsible for messaging and SOA initiatives face a number of challenges in today's enterprise:

• Introducing dynamic behavior and run-time configuration capabilities into a system
• Reusing services that are developed across the enterprise and managing their lifecycle
• Ensuring consistent use of the enterprise services
• Ensuring enterprise services are secure
• Ensuring that the enterprise services comply with the IT policies
• Monitoring and auditing service usage and managing system outages

In short, the goal of the enterprise architect and other specialists is to reuse, streamline, and maintain control over their IT infrastructure. AquaLogic Service Bus is designed to help you achieve these goals.

AquaLogic Service Bus is a true ESB product specifically targeted for service-oriented integration, managing Web Services, and providing traditional message brokering across heterogeneous IT environments. AquaLogic Service Bus's lightweight, stateless, high-performance architecture delivers an intermediary for use as a core element of distributed services networks.

AquaLogic Service Bus is policy-driven. It enables you to establish loose coupling between service clients and business services while maintaining a centralized point of security control and monitoring as shown in the following figure.

 

Figure 1-1 AquaLogic Service Bus High-Level Architecture

 

With AquaLogic Service Bus you implement service integration relationships dynamically through configuration of policies and proxy services. This approach enables your service architectures to evolve rapidly with respect to the following system characteristics:

• Security
• Service location
• Availability and responsiveness
• Data formats
• Logging and monitoring
• Transport protocols and communications paradigms

Because of the intermediary nature of the proxy service, you can use AquaLogic Service Bus to resolve differences between service client and business service requirements in the following areas:

• Payload contents and schema
• Envelope protocols
• Transport protocols
• Point-to-point and publish and subscription protocols
• One way and request/response paradigms
• Synchronous and asynchronous communication
• Security compliance

AquaLogic Service Bus persists policy, proxy service, and related resource configurations in metadata that you can propagate from development through staging to production environments, and then modify as required. The AquaLogic Service Bus message brokering engine accesses this configuration information from its metadata repository.

A key design philosophy of AquaLogic Service Bus is the physical separation of management functions from service implementations. This separation allows implementations to evolve independently and dynamically as driven by the needs of the business without requiring costly infrastructure development efforts. As part of an enterprise's messaging fabric, AquaLogic Service Bus can be used horizontally across many applications and systems, spanning service implementations in different departments built by different teams.

 

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AquaLogic Service Bus Core Feature Set

By fusing the concepts of ESB, message brokering, and Web Services Management (WSM) into a single product, AquaLogic Service Bus provides the foundation for management and integration of messages and services.

The following table describes the core features of AquaLogic Service Bus.

Table 1-1 AquaLogic Service Bus Core Features

For this feature . . .	AquaLogic Service Bus . . .
Routing	Supports the following: Routes messages according to XQuery-based policies or callouts to external Web services. Routing policies apply to both point-to-point and one-to-many routing scenarios (publish). For publish, routing policies serve as subscription filters.
Routing Transport Protocols	Supports the following: File FTP HTTP(S) JMS (including MQ using JMS, and JMS/XA) E-mail (POP/SMTP/IMAP)
Messaging	Supports the following models: Synchronous Asynchronous Publish Subscribe
Message Types	Supports the following message formats: E-mail with attachments JMS with headers MFL (Message Format Language) Raw Data. Raw data is opaque data—that is, non-XML data for which there is no MFL file and therefore no known schema Text SOAP SOAP with attachments XML (XML that is or is not valid against a schema)
Transformations	Supports the following functionality for the transformation or processing of messages: Validates incoming messages against schemas Selects a target service or services, based on the message content or message headers Transforms messages based on the target service Transforms messages based on XQuery or XSLT Supports transformations on both XML and MFL messages Message enrichment Supports call outs to Web services to gather additional data for transformation (for example, country code, full customer records, and so on.)
Logging and Monitoring	Provides a rich set of functionality to audit and monitor services: You can gather statistics about message invocations, errors, performance characteristics, messages passed, SLA violations, and so on. The system also supports logging messages for both systems operations and business auditing purposes, search capabilities, and so on. Incoming messages may be logged to a reporting store. You can extract key information from a message and use as it as a search index. The AquaLogic Service Bus Console provides a cluster-wide view of service status and statistics. Both business services and AquaLogic Service Bus proxy services are monitored, as are response times, message counts, and error counts. Statistics are gathered locally, then aggregated centrally. SLA rules run against aggregated data. The system raises alerts, and you can enable or disable services.
Versioning	Provides the ability to deploy new versions of services and allow you to have multiple versions of message resources such as WSDLs and schemas. Versions can include changes to the WSDL, the message schema, the headers, and the security parameters.
Service Level Agreements	Administrators can set service level agreements (SLAs) on the following attributes of proxy services: Average processing time of a service Processing volume Number of errors, security violations, and schema validation errors Administrators can configure alerts for SLA rule violations
Security	Includes the following: Supports authentication, encryption and decryption, and digital signatures as defined in the Web Services Security (WS-Security) specification. Uses SSL to support traditional transport-level security for HTTP and JMS transport protocols. Supports one-way and two-way certificate based authentication. Supports HTTP basic authentication.
Service Registry	Supports the following: Stores information about services, schemas, transformations, WSDLs (Web Service Definition Language), and WS Policies. Provides centralized management and distributed access Allows you to browse the service registry and import resources into the registry from WebLogic Workshop or other applications. Allows the propagation of configuration data from environment to environment (for example, from a development domain to a test domain to a production domain). The system allows environment specific settings to be overridden during import.
Error Handling	Supports the following: Allows you to configure your system to format and send error messages, and return messages for consumers of services who expect a synchronous response. Allows you to configure error handling for stages in the pipeline, for pipelines, and for proxy services

 

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AquaLogic Service Bus Architecture

AquaLogic Service Bus is an intermediary that takes in messages, processes them to determine where to route them, and transforms them as specified. It receives messages through a transport protocol such as JMS and sends out messages again through the same or another specified transport protocol. Message response follows the inverse path. The message processing by AquaLogic Service Bus is driven by metadata specified as the message flow definition for a proxy service in the AquaLogic Service Bus Console.

Deployment Topology

AquaLogic Service Bus runs on WebLogic Server 9.0 and can be deployed in the following configurations:

• On a single server that also serves as the administration server.
• On a cluster of servers. A cluster consists of a clustered set of managed servers that perform the message processing. A domain has only one cluster and that cluster has AquaLogic Service Bus deployed to it. This cluster can host other applications in addition to AquaLogic Service Bus. There is one administration server in a clustered domain.

AquaLogic Service Bus can manage and control many distributed service endpoints, thereby providing centralization in the enterprise. For example, you can deploy AquaLogic Service Bus as a single hub that manages all the Web service traffic in an enterprise.

You can horizontally scale an AquaLogic Service Bus hub by clustering the underlying WebLogic Server. This allows the messaging load to be homogeneously spread over the servers in the cluster, thereby preventing bottlenecks in the system. In addition, heterogeneous AquaLogic Service Bus hubs can be connected to create a distributed AquaLogic Service Bus network.

AquaLogic Service Bus supports clustering of the WebLogic managed servers. It propagates configuration and metadata automatically to the managed servers for fast local retrieval, and it automatically collects monitoring metrics from all the managed servers for aggregation and display on the AquaLogic Service Bus Console.

The following figure shows the flow of message data in a basic AquaLogic Service Bus cluster topology.

Figure 1-2 Clustering and High Availability

 

Development, Staging, and Production Domains

AquaLogic Service Bus supports best practices for change management in your enterprise systems by enabling you to configure resources and services in a controlled environment. You can then export the configurations for import into separate staging domains for testing and final preparation for promotion into a production domain. AquaLogic Service Bus provides you with the ability to reconfigure environment-specific elements as necessary to meet the requirements of the importing domain.

 

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AquaLogic Service Bus Message Brokering

AquaLogic Service Bus provides intelligent message brokering functionality for your SOA. The following sections describe the key concepts associated with AquaLogic Service Bus message structures and message processing.

Business Services and Proxy Services

AquaLogic Service Bus provides intelligent message brokering between business services (such as enterprise services and databases) and service clients (such as presentation applications or other business services) through proxy services that you configure using the AquaLogic Service Bus Console.

Business Services

Business services are AquaLogic Service Bus definitions of the enterprise services with which you want to exchange messages. Using the AquaLogic Service Bus Console, you configure a business service by defining its interface in terms of WSDLs and the type of transport it uses, its security requirements, and other characteristics.

For information on how to configure a business service using the AquaLogic Service Bus Console, see "Adding a Business Service" in Business Services in the AquaLogic Service Bus Console Online Help.

Proxy Services

Proxy services are AquaLogic Service Bus definitions of intermediary Web services that are hosted locally on AquaLogic Service Bus. Using the AquaLogic Service Bus Console, you configure a proxy service by defining its interface in terms of WSDLs and the type of transport it uses, the logic of message processing in message flow definitions, and by configuring policies.

With AquaLogic Service Bus message brokering, service clients exchange messages with an intermediary proxy service instead of directly with a business service. A proxy service can have an interface that is identical (same WSDL and transport) to a business service with which the proxy service communicates, or the proxy service can have an interface that differs from that of the business service in terms of WSDL, transport type, or both.

Since a proxy service can route messages to multiple business services, you can choose to configure a proxy service with an interface that is independent of the business services with which the proxy service communicates. In such cases, you would configure a message flow definition to route a message to the appropriate business service and map the message data into the format required by the business service's interface.

For more information about the structure of proxy services, see Message Flow Definition.

Message Processing

A message is a formula used by WebLogic Server to share information among applications. Messages can contain data or status information about application processes, or instructions for the recipient, or both. AquaLogic Service Bus enables you to route messages based on their contents and to perform transformations on that content.

The processing of messages occurs in the following sequence of events:

Processing of the inbound transport
Message flow execution
Processing of the outbound transport

After a message is sent to an endpoint (either a business service or another proxy service),AquaLogic Service Bus processes the response message in a similar model as that described in the preceding sequence of events.

The following figure shows a high-level view of how messages flow through AquaLogic Service Bus, from inbound endpoint (a proxy service) to outbound endpoint (the transport URL for a service—typically a business service).

Figure 1-3 AquaLogic Service Bus Message Processing

 

The following sections describe each layer involved in this message processing.

Transport Layer (Inbound)

The first step for the message is the inbound transport layer, which is responsible for handling communication with the service client endpoint and acts as the entry point for messages into AquaLogic Service Bus. It supports a variety of communication protocols, such as HTTP and JMS. With regard to the message data itself, the inbound transport layer primarily deals with raw bytes in the form of input/output streams.

The inbound transport layer is simply for getting messages into the AquaLogic Service Bus system and sending the response back. It does not perform any data processing.

Message Flow Definition

Pipelines, branches, and route nodes define the implementation of AquaLogic Service Bus proxy services. Using the AquaLogic Service Bus Console, you configure the logic for the manipulation of messages in proxy service message flow definitions. This logic includes such activities as transformation, publishing, and reporting which are implemented as individual actions within the stages of a pipeline.

Pipeline Pairs

Pipeline logic occurs in pairs of definitions consisting of a request pipeline definition and a response pipeline definition. The request pipeline definition specifies the actions that AquaLogic Service Bus performs on request messages to the proxy service before invoking a business service or another proxy service. The response pipeline definition specifies the processing that AquaLogic Service Bus performs on responses from the service invoked by the proxy service before the proxy service returns a response. Routing is performed by a route node at the end of the message flow.

Note: WS-Security processing and authorization are transparently performed before pipeline execution.

Pipeline Execution Stages and Actions

Each pipeline is a sequence of stages. A stage is a user-configured processing step such as transformation or publishing. Messages fed into the pipelines are accompanied by a set of message context variables that contain the message contents and can be accessed or modified by actions in the pipeline stages.

The following table describes all of the actions possible in a AquaLogic Service Bus pipeline stage.

Table 1-2 Actions in a Pipeline Stage

Actions	What Happens
Transformation	Transformation actions affect the message context. A Web services callout can be an alternative to an XQuery or XSLT transformation to set the output context variable. Inplace updates to transform a single context variable are also supported.
Branching	Branching actions allow the use of nested if structures to select a transformation.
Publish	A publish action enables you to define the set of endpoints to which the message is published. You use a publish action to send a copy of the message to a set of listeners during the message flow. You can define a set of XQuery or XSLT transformations that affects context variables before the message is published to each endpoint. Alternatively, you can specify that a Web services callout be used to set the context variable. The changes to the predefined context variables in the publish request actions are isolated to that publish endpoint and do not affect subsequent processing by the message flow.
Reporting	A reporting action enables writing of a reporting record with user-defined information from the context so that you can use the AquaLogic Service Bus Console to search and display this information.
Jump	Jump actions terminates processing in a stage. Typical use of these actions would be for error handling or to skip to the next stage in the pipeline.
Logging	A logging action enables logging of selected context to the WebLogic Server system log for debugging purposes.
Validation	A validation action validates a document against an XML or WSDL schema.

 

Operational Pipelines

Each pipeline consists of a sequence of stages containing actions. However a single service level request pipeline might optionally branch out into operational pipelines (at most one per operation and optionally a default operational pipeline). The determination of the operation is done through user-selected criteria. The response processing starts with the relevant operation pipeline which then joins into a single service-level response pipeline.

The following figure shows an example of operation pipelines in a proxy service:

Figure 1-4 Example Message Flow

 

In the case of one-way operations, the response pipeline is executed with an empty message. This permits a response to be constructed for the proxy service, thus enabling bridging between request/response and one-way operations. The bridging mechanism means that proxy service input can be one-way while its output is request/response or vice versa. The proxy service either absorbs the response from the invoked service or generates one for the client.

Transport Layer (Outbound)

The outbound transport layer is responsible for handling communication with the destination endpoint. It supports a variety of communication protocols, such as HTTP and JMS. With regard to the message data itself, the transport layer primarily deals with raw bytes in the form of input/output streams.

The outbound transport layer is simply for getting messages out of the AquaLogic Service Bus system. It does not perform any data processing.