HornetQ Persistence Concepts

Internal

• WildFly HornetQ-Based Messaging Subsystem Concepts

Overview

This article provides a high level overview of the HornetQ persistence concepts. It will describe what kind of data is persisted, as well as where and when. It will also discuss paging, which is a protection mechanism against running out of memory; persistence is relevant in this context because messages that do not fit in memory go to the filesystem, even if the messages themselves are marked as non-persistent.

There is No Database

Unlike other messaging systems, which do offer the option of storing message data in a relational database, HornetQ does not. For reasons that led to this decision see https://developer.jboss.org/thread/153581. More details in "Messaging persistence in EAP 6.x" https://access.redhat.com/solutions/226743.

What Does HornetQ Persist?

Naturally, HornetQ persists persistent messages.

Persistent Messages

All persistent messages must be stored on persistent storage, as mandated by the JMS specification. This is necessary to protect against messaging system failure: a persistent message can be presumably recovered from the persistent storage and re-sent.

Journal

When a node is started for the first time it persists a unique identifier into its journal directory. This ID is needed for proper formation of clusters.