Patterns. Broker Interactions for Intra- and Inter-Enterprise

9.2 IBM WebSphere Business Integration Message Broker

WebSphere Business Integration Message Broker enables information, packaged as messages, to flow between different business applications. With this new product, the functions of WebSphere MQ Integrator and WebSphere MQ Event Broker have merged into one product consisting of:

• WebSphere Business Integration Message Broker providing broker functionality for point-to-point messaging.

• WebSphere Business Integration Event Broker providing pub/sub functionality.

During installation, you can elect to install just Event Broker, or Event Broker and Message Broker (Event Broker is a prerequisite for Message Broker).

9.2.1 Architectural overview

WebSphere Business Integration Message Broker (Figure 9-1) consists of the following components:

• Message Brokers Toolkit for WebSphere Studio, which is a new feature replacing the Control Center of WebSphere MQ Integrator V2.1, as well as adding extended functionality in many new areas. For brevity, we refer to it as the Message Brokers Toolkit.

• Configuration Manager, which contains a repository for configurations and messages

• User Name Server, which is used for publish/subscribe security functionality

• Publish / subscribe functionality.

• WebSphere MQ queue manager(s), which provide the underlying transport infrastructure for the WebSphere Business Integration Message Broker

• User application programs, which generate messages and request them to be transformed and routed to other destinations in a messaging infrastructure, according to specific business rules

• Message broker(s), the runtime component consisting of execution groups, containing deployed message flows.

Figure 9-1: WebSphere Business Integration Message Broker architecture

Message Brokers Toolkit

The Message Brokers Toolkit integrated development environment provides an environment to perform application development and broker administration tasks for message brokers. The Message Brokers Toolkit is an Eclipse-based workbench tool, available on the Windows 2000 and XP platform. It is also available as a plugin for WebSphere Studio Application Developer - Integrated Edition.

The Message Brokers Toolkit consists of a workbench window which displays one or more perspectives. A perspective is a group of views and editors required to perform tasks associated with a role. The two primary perspectives used for the development and deployment of message flows are as follows:

• The Broker Application Development perspective is used for application development tasks and is the default perspective shown when the Message Brokers Toolkit is first started. It is used to:

  • Develop message flows and message sets

  • Deploy message flows and message sets to the broker

  • Put and get messages from queues for debugging purposes

• The Broker Administration perspective is used to perform tasks to manage one or more brokers. It is used to:

  • Create and manage broker domains and topology

  • Create and manage execution groups

  • Create and deploy broker archive (bar) files to execution groups

  • Manage publish/subscribe topics and subscriptions

  • Manage event logs and alerts

A single Message Brokers Toolkit can connect to multiple Configuration Managers allowing it to manage multiple broker domains.

The broker administration functions are also available as command line utilities. This allows for scripting of commands to enable automated operation for such tasks as deployment and configuration.

Configuration Manager

The Configuration Manager is the central runtime component that manages the components and resources that constitute the broker domain.

The Configuration Manager has four main functions:

• Maintains configuration details in the configuration repository. This is a set of database tables that provide a central record of the broker domain components.

• Deploys the broker topology and message processing operations in response to actions initiated through the workbench. Broker archive (bar) files are deployed through the Configuration Manager to the execution groups within a broker.

• Reports on the results of deployment and the status of the broker.

• Communicates with other components in the broker domain using WebSphere MQ transport services.

You need to install, create and start a Configuration Manager for each broker domain.

Broker

A broker is the named resource that executes the business logic defined in the message flows. Applications send and receive messages to and from a broker. The broker routes each message using the rules defined in message flows and message sets, and transforms the data into the structure required by the receiving application.

Brokers are grouped into broker domains. Each domain is coordinated by a Configuration Manager. There can be many brokers, and each can be running on a different system. This provides protection against failure, and can separate work across different divisions in a business.

More than one broker can be defined per WebSphere Business Integration Message Broker V5 domain, either on the same or on a different physical system. If you plan to use the publish/subscribe service, you can connect a number of brokers together into a collective, which allows optimization of the subscriber connections.

The broker uses MQ sender and receiver channels to communicate with the Configuration Manager and other brokers in the broker domain.

Execution groups

Brokers contain execution groups that run as a separate operating system process, providing an isolated runtime environment for a set of deployed message flows. A single default execution group is set up ready for use when you create a broker in the workbench. By setting up additional execution groups, you can isolate message flows that handle sensitive data such as payroll records, or security information, or unannounced product information, from other non-sensitive message flows.

Applications

Applications in WebSphere Business Integration Message Broker consist of message flows running on a broker that control the flow and manipulation of messages as they pass through the broker.

WebSphere Business Integration Message Broker supports two models for application communication:

• Point-to-Point, which can include one-to-many and many-to-one (where the number of message producers and the number of message receivers are different).

• Publish/Subscribe, which includes and extends the existing MQSeries publish/subscribe model.

Message flows

Message flows consist of a number of nodes (or primitives) which are wired together to form a broker application. Each node represents a processing step, and the connections in the flow determine which processing steps are carried out, and in which order. Each node has terminals for input or output, or both (most nodes have several output terminals).

There are many other IBM primitive nodes available. Each node will have properties which can be set to certain values for the parameters of the node. In addition, WebSphere Business Integration Message Broker allows you to create custom nodes.

Message flows allow you to:

• Route messages based on the content of the message.

• Transform messages from one format to another. For example, a message flow can receive an incoming message using an IP adapter and send it out using an MQ adapter.

• Manipulate messages by modifying, combining, adding or removing data fields. More complex manipulation of message data can be achieved by using Extended SQL (ESQL).

• Access information stored in databases.

Message sets

The broker can handle both self-defining messages which contain a definition of their structure and format, and those that don't. Message definitions stored in message sets can be used by the broker to understand the format of those messages that don't contain the information needed.

Publish / subscribe

With the publish / subscribe (pub/sub for short), a publishing application sends a message about a named topic to a broker. The broker passes the published message to those applications that have registered an interest in that topic. The publisher and the subscriber are unaware of the other's existence.

The broker handles the distribution of messages between publishing applications and subscribing applications. Applications can publish on, or subscribe to, many topics as well as apply more sophisticated filtering mechanisms.

An optional User Name Server in the broker domain controls who is authorized to publish or subscribe to topics. Topic-based security is set up and administered from the Message Brokers Toolkit. User permissions are set at individual or group level using Access control lists.

The WebSphere Business Integration Event Broker supports two transport mechanisms for publish/subscribe:

• MQ-based pub/sub

• IP-based pub/sub

An important feature of the WBI Event Broker pub/sub is its cross-stream support. This means that IP-connected subscribers can receive messages from both IP- and MQ-connected publishers, the same being true for MQ-connected subscribers.

With MQ-based pub/sub, clients (publishers and subscribers) can connect to the broker queues just as any MQSeries application can - that is, either via a client connection over TCP/IP, or directly to a local queue manager using a "bindings" connection.

IP-based pub/sub support is new to the WebSphere MQ family. Instead of using MQSeries queues as the application-broker interface, TCP/IP sockets are used. The broker listens on a particular port for incoming requests from publishers and subscribers, and once these are accepted, a TCP/IP socket is set up between the broker and each client.

Since interaction with the broker totally bypasses MQSeries queues, there is the potential for substantial performance gains. The trade-off is the reduced Quality of Service: all messages published over IP are non-persistent, transactionality is unsupported, and subscriptions are non-durable. However, for certain applications-for example, real-time stock quotes-this is not an issue.

Transport support for applications

WebSphere Business Integration Message Broker provides the following transports mechanisms to allow clients to communicate with applications through message flows:

• WebSphere MQ Web Services Transport allows Web services clients using XML messages and the HTTP protocol running over TCP/IP to communicate with applications through message flows in a broker.

• WebSphere MQ Real-time Transport is a lightweight protocol optimized for use with non-persistent messaging. JMS applications communicate with the broker using TCP/IP ports.

• WebSphere MQ Telemetry Transport is a lightweight publish/subscribe protocol flowing over TCP/IP. This protocol is used by specialized applications on small footprint devices that require a low bandwidth communication, typically for remote data acquisition and process control.

• WebSphere MQ Multicast Transport is used by dedicated multicast-enabled JMS application clients to connect to brokers. Applications communicate with the broker by writing data directly to TCP/IP ports. This protocol is optimized for high volume, one-to-many publish/subscribe topologies.

• WebSphere MQ Enterprise Transport supports WebSphere MQ applications that connect to WebSphere Business Integration Message Broker by writing data to and reading data from message queues.

• WebSphere MQ Mobile Transport is used exclusively by WebSphere MQ Everyplace clients. WebSphere MQ Everyplace is an application designed primarily for messaging to, from, and between pervasive devices. These are typically small, handheld devices, such as mobile phones and PDAs. A bridge queue on the broker's queue manager provides an interface for the WebSphere MQ Everyplace clients to the broker services.