Sun Java System Message Queue 4.3 Administration Guide

Configuring Broker Clusters

You create a broker cluster by specifying cluster configuration properties for each of its member brokers. Except where noted in this chapter, cluster configuration properties must be set to the same value for each broker in a cluster. This section introduces these properties and the use of a cluster configuration file to specify them:

The Cluster Configuration File

Like all broker properties, cluster configuration properties can be set individually for each broker in a cluster, either in its instance configuration file ( or by using the -D option on the command line when you start the broker. However, except where noted in this chapter, each cluster configuration property must be set to the same value for each broker in a cluster.

For example, to specify the transport protocol for the cluster connection service, you can include the following property in the instance configuration file for each broker in the cluster: imq.cluster.transport=ssl. If you need to change the value of this property, you must change its value in the instance configuration file for every broker in the cluster.

For consistency and ease of maintenance, it is generally more convenient to collect all of the common cluster configuration properties into a central cluster configuration file that all of the individual brokers in a cluster reference. Using a cluster configuration file prevents the settings from getting out of synch and ensures that all brokers in a cluster use the same, consistent cluster configuration information.

When using a cluster configuration file, each broker’s instance configuration file must point to the location of the cluster configuration file by setting the imq.cluster.url property. For example,


Note –

A cluster configuration file can also include broker properties that are not used specifically for cluster configuration. For example, you can place any broker property in the cluster configuration file that has the same value for all brokers in a cluster. For more information, see Connecting Brokers into a Conventional Cluster

Cluster Configuration Properties

This section reviews the most important cluster configuration properties, grouped into the following categories:

A complete list of cluster configuration properties can be found in Table 16–11

Cluster Connection Service Properties

The following properties are used to configure the cluster connection service used for internal communication between brokers in the cluster. These properties are used by both conventional and enhanced clusters.

Conventional Broker Cluster Properties

The following properties, in addition to those listed in Cluster Connection Service Properties, are used to configure conventional clusters:

Enhanced Broker Cluster Properties

Enhanced broker clusters, which share a JDBC-based data store, require more configuration than do conventional broker clusters. In addition to the properties listed in Cluster Connection Service Properties, the following categories of properties are used to configure an enhanced cluster:

Enhanced Clusters: General Configuration Properties

Enhanced Clusters: JDBC Configuration Properties

The persistent data store for an enhanced cluster is maintained on a highly-available JDBC database.

The highly-availabile database may be Sun’s MySQL Cluster Edition or High Availability Session Store (HADB), or it may be an open-source or third-party product such as Oracle Corporation’s Real Application Clusters (RAC). As described in JDBC-Based Persistence Properties, the imq.persist.jdbc.dbVendor broker property specifies the name of the database vendor, and all of the remaining JDBC-related properties are qualified with this vendor name.

The JDBC-related properties are discussed under JDBC-Based Persistence Properties and summarized in Table 16–6. See the example configurations for MySQL and HADB in Example 8–1 and Example 8–2, respectively.

Note –

In setting JDBC-related properties for an enhanced cluster, note the following vendor-specific issues:

Enhanced Clusters: Failure Detection Properties

The following configuration properties (listed in Table 16–11) specify the parameters for the exchange of heartbeat and status information within an enhanced cluster:

Smaller values for these heartbeat and monitoring intervals will result in quicker reaction to broker failure, but at the cost of reduced performance and increased likelihood of false suspicions and erroneous failure detection.

Displaying a Cluster Configuration

To display information about a cluster’s configuration, use the Command utility’s list bkr subcommand:

   imqcmd list bkr

This lists the current state of all brokers included in the cluster to which a given broker belongs. The broker states are described in the following table:

Table 10–1 Broker States

Broker State 



Broker is operating 


For enhanced clusters, broker has begun taking over persistent data store from another broker


For enhanced clusters, broker has finished taking over persistent data store from another broker 


For enhanced clusters, attempted takeover has failed 


Broker has begun quiescing 


Broker has finished quiescing 


Broker has begun shutting down 


Broker is down 


Broker state unknown 

The results of the imqcmd list bkr command are shown in Example 10–1 (for a conventional cluster) and Example 10–2 (for an enhanced cluster).

Example 10–1 Configuration Listing for a Conventional Cluster

Listing all the brokers in the cluster that the following broker is a member of:

Host         Primary Port
localHost    7676

Cluster Is Highly Available             False

Address         State
whippet:7676    OPERATING
greyhound:7676  OPERATING

Example 10–2 Configuration Listing for an Enhanced Cluster

Listing all the brokers in the cluster that the following broker is a member of:

Host         Primary Port    Cluster Broker ID
localHost    7676            brokerA

Cluster ID                              myClusterID
Cluster Is Highly Available             True

                                                                           ID of broker       Time since last
Broker ID       Address         State                   Msgs in store   performing takeover   status timestamp
brokerA         localhost:7676  OPERATING               121                                   30 sec
brokerB         greyhound:7676  TAKEOVER_STARTED        52              brokerA               3 hrs
brokerC         jpgserv:7676    SHUTDOWN_STARTED        12346                                 10 sec
brokerD         icdev:7676      TAKEOVER_COMPLETE       0               brokerA               2 min
brokerE         mrperf:7676     *unknown                12                                    0 sec
brokerG         iclab1:7676     QUIESCING               4                                     2 sec
brokerH         iclab2:7676     QUIESCE_COMPLETE        8                                     5 sec