Appendix B Message Queue Features

The Message Queue service fully implements the JMS 1.1 specification for reliable, asynchronous, flexible message delivery For information about JMS compliance-related issues, see Appendix A, "Message Queue Implementation of Optional JMS Functionality." However, Message Queue has capabilities and features that exceed JMS requirements. You can use these features to integrate and monitor systems consisting of large numbers of distributed components exchanging many thousands of messages in round-the-clock, mission-critical operations.

This book has introduced these features in the process of describing the Message Queue service. For your convenience, this appendix provides a summary of Message Queue features: each feature is briefly described, the work required to use the feature is summarized, and references are provided to sections in this book that introduce these features and to the specific documents in the Message Queue documentation set that describe these features in detail.

Message Queue’s features, listed alphabetically in Table B-1, can be roughly divided into the categories shown below.

Integration Support

J2EE resource adapters

Security

Authentication

Authorization

Encryption (see Secure connections)

Scalability

Thread managementt

Thread management

Availability

Memory resource management

Message flow control to clients

Automatic reconnect

Reliable data persistence

Connection ping

Manageability

Administration tools

Message-based monitoring API

Tunable performance

Configurable physical destinations

Broker configuration

Dead message queue

Flexible Server Configuration

Configurable persistence

LDAP Server support

JNDI service provider support

Performance

Message compression

Tunable performance

Configurable physical destinations

Table B-1 Message Queue Features
Feature	Description and Reference
Administration tools	The Message Queue service includes GUI and command line tools for managing destinations, transactions, durable subscriptions, administered object stores, user repositories, JDBC-compliant data stores, and server certificates. Reference Administration Tools. “Administration Tasks and Tools” in Message Queue Administration Guide.
Authentication	Authenticate users seeking a connection to the broker. The Message Queue service allows users to connect to the broker by validating their name and password against values stored in a user repository. The repository can be a flat-file repository shipped with Message Queue or an LDAP repository (LDAP v2 or v3 protocol). To Use Create a user repository or use the default instance. Use the imqusermgr tool to populate the repository Reference Authentication and Authorization. “Managing Security,” Message Queue Administration Guide.
Authorization	Authorize users to perform specific operations. The Message Queue service allows you to create an access control properties file that specifies the operations users and groups of users can perform. The broker checks this file when a client seeks to create a connection, create a producer, create a consumer, or browse a queue. To Use Edit the access control properties file that is automatically created for the broker instance. Reference Authentication and Authorization “Managing Security,” Message Queue Administration Guide.
Automatic reconnect	The administrator sets connection attributes on the connection factory administered object to enable automatic reconnection in the event of connection failure. Reconnection can be to the same broker or to another broker in a cluster if a cluster is used. You can specify how many times to try reconnection and the interval between attempts. For clustered brokers, you can also specify how often to iterate through a list of brokers and whether to iterate through the list in a specific order. Reference Connection Services. “Managing Administered Objects,” “Administered Object Attribute Reference” in Message Queue Administration Guide.
Broker clusters	The administrator can balance client connections and message delivery across a number of broker instances by grouping those instances into a broker cluster. To Use Specify cluster configuration properties for each broker in the cluster. You can do this using a configuration file or by setting properties for each broker. If there is a master broker, start the master broker Start the other brokers in the cluster. Reference Chapter 4, "Broker Clusters." “Working With Clusters,” Message Queue Administration Guide.
Broker configuration	The administrator can set broker properties to tune Message Queue service performance. This includes routing services, persistence services, security, monitoring, and administered object management. Reference Chapter 3, "Message Queue Service." “Configuring the Broker,” “Broker Properties Reference” in Message Queue Administration Guide
C client support	C clients can use Message Queue messaging services to send and receive messages. The C API enables legacy C applications and C++ applications to participate in JMS-based messaging. Message Queue’s C API is supported by a C client runtime that supports most of the standard JMS functionality, with the exception of the following: the use of administered objects; map, stream, or object message body types; distributed transactions; and queue browsers. The C client runtime also does not support most of Message Queue’s enterprise features. Reference Java and C Clients. Message Queue Developer’s Guide for C Clients
Compressed messages	Java clients can set a message property to have the client runtime compress a message being sent. The runtime on the consumer side decompresses the message before it delivers it to the consumer. Additional properties are provided that you can use to determine whether compressing messages would actually improve performance. Reference Message Body. “Message Queue Clients: Design and Features” in Message Queue Developer’s Guide for Java Clients.
Configurable persistence	The administrator can configure the broker to use the file-based persistent store provided with Message Queue or a JDBC-compliant database, such as Oracle 8i. To Use Set broker properties that relate to file-system persistent storage or JDBC-compliant storage. Reference Persistence Services. “Configuring the Broker” in Message Queue Administration Guide.
Configurable physical destinations	The administrator can define some messaging behavior by setting physical destination properties when creating destinations. The following behavior can be configured for any destination: the maximum number of unconsumed messages or the maximum amount of memory allowed for such messages, which messages the broker should reject when memory limits are reached, the maximum number of producers and consumers, the maximum message size, the maximum number of messages delivered in a single batch, whether the destination can deliver only to local consumers, and whether dead messages on the destination can be moved to the dead message queue. Reference Destinations and Routing Services. “Managing Physical Destinations,” “Physical Destination Properties Reference” in Message Queue Administration Guide.
Connection ping	The administrator can set a connection factory attribute to specify the frequency of a ping operation from the client runtime to the broker. This allows the client to preemptively detect a filed connection. Reference Connection Services. “Connection Factory Attributes” in Message Queue Administration Guide.
Dead message queue	The Message Queue message service creates the dead message queue to hold messages that have expired or that the broker could not process. You can examine the contents of the queue to monitor, tune, or troubleshoot system performance. Reference Destinations and Routing Services. “Managing Physical Destinations” Message Queue Administration Guide.
HTTP connections	Java clients can create HTTP connections to the broker. HTTP transport allows messages to be delivered through firewalls. Message Queue implements HTTP support using an HTTP tunnel servlet that runs in a web server environment. Messages produced by a client are wrapped by the client runtime as HTTP requests and delivered over HTTP through a firewall to the tunnel servlet. The tunnel servlet extracts the JMS message from the HTTP request and delivers the message over TCP/IP to the broker. To Use Deploy HTTP tunnel servlet on a web server. Configure broker’s httpjms connection service and start the broker. Configure HTTP connection Obtain an HTTP connection to the broker. (Java clients only.) Reference Connecting to the Broker. Appendix C “Enabling HTTP Support,” Message Queue Administration Guide
Interactive monitoring	The administrator can use the imqcmd metrics command to monitor a broker remotely. Monitored data includes JVM metrics, broker message flow, connections, connection resources, messages, destination message flow, destination consumers, destination resource use. Reference Monitoring Services. “Monitoring a Message Server” in Message Queue Administration Guide
J2EE resource adapters	Message Queue provides a resource adapter that can be plugged into a J2EE-compliant application server. By using Message Queue as a JMS provider, an application server meets the J2EE requirement that distributed components running in the application server be able to interact using reliable, asynchronous message. To Use Configure the adapter by setting adapter attributes. Reference J2EE Application Server Support. “JMS Resource Adapter Attribute Reference,” Message Queue Administration Guide.
JNDI service provider support	Clients can look up administered objects using the JNDI API. Administrators can use the imqobjmgr utility to add, list, update, and delete administered objects in an object store accessible using JNDI. Reference .Administration Tools “Command Reference” in Message Queue Administration Guide
LDAP Server support	The administrator can use LDAP servers for administered object store and for storing user information needed for authentication and authorization. By default Message Queue provides file-based storage for this data. To Use for Administered Objects Use the tools provided by the vendor to populate and manage the user repository. Set the LDAP-related broker properties. Set up access control for administrative users. Reference “Managing Security” Message Queue Administration Guide To Use for User Repository Use the tools provided by the vendor to set up the LDAP server. Set the LDAP-related broker properties to define the initial context and the location of the store. Set the LDAP-related broker properties that relate to securing the LDAP server operations. Reference Security Services. “Managing Administered Objects” Message Queue Administration Guide
Memory resource management	The administrator can configure the following behavior: Set properties on a destination to specify the maximum number of producers, the maximum number of size of messages, and the maximum size of any one message. Set properties on a destination to control message flow Set properties on a destination to manage message flow for each destination Set properties on the broker to specify message limits on all destinations for that broker. Set properties on the broker to specify thresholds of available system memory at which the broker takes increasingly serious action to prevent memory overload. The action taken depends on the state of memory resources. Reference Destinations and Routing Services. “Configuring the Broker,” “Broker Properties Reference,” “Physical Destination Property Reference” in Message Queue Administration Guide
Message compression	The developer can set a message header property to have the client runtime compress a message before sending it. The client runtime decompresses the message before delivering it to the consumer. Reference Message Properties. “Message Compression” in Message Queue Developer’s Guide for Java Clients.
Message flow control to clients	The administrator or the developer can configure a connection to specify various flow limits and metering schemes to minimize the collision of payload and control messages, and thereby to maximize message throughput. To Use Set the flow-control attributes for the connection factory administered object (administrator), or set the flow-control properties for the connection factory (developer). Reference Connection Factories and Connections. “Managing Administered Objects,” “Administered Object Attribute Reference” in Message Queue Administration Guide.
Message-based monitoring API	Java clients can use a monitoring API to create custom monitoring applications. A monitoring application is a consumer that retrieves metrics messages from special metrics topic destinations. To Use Write a metrics monitoring client. Set broker properties to configure the broker’s metrics message producer. Set access controls on metrics topic destinations. Start the monitoring client. Reference Monitoring Services. “Using the Metrics Monitoring API” in Message Queue Developer’s Guide for Java Clients. “Monitoring a Message Server” in Message Queue Administration Guide.
Queue delivery to multiple consumers	Clients can register more than one consumer for a given queue. The administrator can specify the maximum number of active consumers and the maximum number of backup consumers for the queue. The broker distributes messages to the registered consumers, balancing the load among them in order to allow the system to scale. To Use Set physical destination properties maxNumActiveConsumers and maxNumBackupConsumers. Reference Point-To-Point Messaging. “Physical Destination Properties” and “Multiple Consumer Queue Performance,” Message Queue Administration Guide.
Reliable data persistence	To obtain absolute reliability you can require that the operating system write the data synchronously to the persistent store by setting the imq.persist.file.sync.enabled property to true. This eliminates possible data loss due to system crashes, but at the expense of performance. Note that although the data is not lost, it is not available to any other broker (in a cluster) because data is not currently shared by clustered brokers. When the system comes back up, the broker can reliably resume operations. Reference Persistence Services. “Broker Properties Reference” in Message Queue Administration Guide.
Secure connections	Clients can secure transmission of messages using the Secure Socket Layer (SSL) standard over TCP/IP and HTTP transports. These SSL-based connection services allow for the encryption of messages sent between clients and broker. SSL support is based on self-signed server certificates. Message Queue provides a utility that generates a private/public key pair and embeds the public key in a self-signed certificate. This certificate is passed to any client requesting a connection to the broker, and the client uses the certificate to set up an encrypted connection. To Use Generate a self-signed or signed certificate. Enable the secure service. Start the broker Configure client security connection properties and run the client. Reference Connecting to the Broker. Security Services. “Managing Security” Message Queue Administration Guide. Message Queue Developer’s Guide for Java Clients Message Queue Developer’s Guide for C Clients
SOAP support	Clients can receive SOAP (XML) messages and they can wrap them as JMS messages and use Message Queue to exchange them as they would a JMS message. Clients can use a special servlet to receive SOAP messages; they can use a utility class to wrap a SOAP message as a JMS message; they can use another utility class to extract the SOAP message from the JMS message. Clients can use standard SAAJ libraries to assemble and disassemble a SOAP message. Reference Working with SOAP Messages. “Working With SOAP Message,” Message Queue Developer’s Guide for Java Clients.
Thread management	The administrator can specify the maximum and minimum number of threads assigned to any specific connection service. The administrator can also determine whether a connection service could increase throughput by using a shared thread model, which allows threads dedicated to idle connections to be used by other connections. To Use Set connection service thread-related properties. Reference Thread Pool Management. “Configuring a Broker,” Message Queue Administration Guide.
Tunable performance	The administrator can set broker properties to adjust memory usage, threading resources, message flow, connection services, reliability parameters, and other elements that affect message throughput and system performance. Reference Monitoring Services. “Monitoring a Message Server” and “Analyzing and Tuning a Message Service” in Message Queue Administration Guide

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