Sun Java System Message Queue 4.2 Technical Overview

Cluster Models Compared

Conventional and high-availability cluster models share the same basic infrastructure. They both use the cluster communication service to enable message delivery between producers and consumers across the cluster. However, as shown in the following figure and described in previous sections, these models differ in how destination and consumer information is synchronized across the cluster, in the mechanisms for detecting failure, in how client reconnect takes place.

Figure 4–4 Cluster Infrastructure

Diagram comparing conventional and high-availability
broker cluster infrastructures. Figure explained in the text.

In addition, while both models rely on the broker's persistence interfaces (both flat-file and JDBC), in the case of high-availability clusters the shared data store must be a highly-available JDBC database (a highly-available file-based data store has not yet been implemented).

The following table summarizes the functional differences between the two cluster models. This information might help in deciding which model to use or whether to switch from one to another.

Table 4–1 Clustering Model Differences


Functionality	Conventional	High-Availability
Performance	Faster than high-availability cluster model.	Slower than conventional cluster model
Service availability	Yes, but some operations are not possible if master broker is down.	Yes.
Data availability	No. State information in failed broker is not available.	Yes at all times.
Transparent recovery from failure	No. Message delivery is interrupted. Also, client reconnects might not be possible if failure occurs during a transaction commit (rare).	Yes. No interruption in message delivery. If failure occurs during a transaction commit, an exception might be thrown indicating that the transaction could not be committed (extremely rare).
Configuration	Set appropriate cluster configuration properties for each broker.	Set appropriate cluster configuration properties for each broker.
Additional requirements	None.	Highly-available database.
Restricted to subnet	No.	Yes.