High-Availability Cluster Properties

High-availability 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 a high-availability cluster:

• High-Availability Clusters: General Configuration Properties

• High-Availability Clusters: JDBC Configuration Properties

• High-Availability Clusters: Failure Detection Properties

High-Availability Clusters: General Configuration Properties

• imq.cluster.ha is a boolean value that specifies if the cluster is high-availability cluster (true) or a conventional broker (false). The default value is false.

  If set to true, the high-availability mechanisms for failure detection and takeover of a failed broker are enabled. High-availability clusters are self-configuring: any broker configured to use the cluster’s shared data store is automatically registered as part of the cluster, without further action on your part. If the conventional cluster property, imq.cluster.brokerlist, is specified for a high–availability broker, the property is ignored and a warning message is logged at broker startup.

• imq.persist.store specifies the model for a broker's persistent data store. This property must be set to the value jdbc for every broker in a high-availability cluster.

• imq.cluster.clusterid specifies the cluster identifier, which will be appended to the names of all database tables in the cluster’s shared persistent store. The value of this property must be the same for all brokers in a given cluster, but must be unique for each cluster: no two running clusters may have the same cluster identifier.

• imq.brokerid is a broker identifier that must be unique for each broker in the cluster. Hence, this property must be set in each broker's instance configuration file rather than in a cluster configuration file.

High-Availability Clusters: JDBC Configuration Properties

The persistent data store for a high-availability 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.

In setting JDBC-related properties for a high-availability cluster, note the following vendor-specific issues:

• MySQL Cluster Edition

  When using MySQL Cluster Edition as a highly-available database, you must specify the NDB Storage Engine rather than the InnoDB Storage Engine set by Message Queue by default. To specify the NDB Storage Engine, set the following broker property for all brokers in the cluster:

  imq.persist.jdbc.mysql.tableoption=ENGINE=NDBCLUSTER

• HADB

  When using HADB in a Sun Java Application Server environment, if the integration between Message Queue and Application Server is local (that is, there is a one-to-one relationship between Application Server instances and Message Queue brokers), the Application Server will automatically propagate HADB-related properties to each broker in the cluster. However, if the integration is remote (a single Application Server instance using an externally configured broker cluster), then it is your responsibility to configure the needed HADB properties explicitly.

High-Availability 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 a high-availability cluster:

• imq.cluster.heartbeat.hostname specifies the host name (or IP address) for the heartbeat connection service.

• imq.cluster.heartbeat.port specifies the port number for the heartbeat connection service.

• imq.cluster.heartbeat.interval specifies the interval, in seconds, at which heartbeat packets are transmitted.

• imq.cluster.heartbeat.threshold specifies the number of missed heartbeat intervals after which a broker is considered suspect of failure.

• imq.cluster.monitor.interval specifies the interval, in seconds, at which to monitor a suspect broker’s state information to determine whether it has failed.

• imq.cluster.monitor.threshold specifies the number of elapsed monitor intervals after which a suspect broker is considered to have failed.

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.