What's New in HiveMQ 4.40?

The HiveMQ team is excited to announce the release of HiveMQ Enterprise MQTT Platform 4.40. This release introduces a new mandatory start option for HiveMQ extensions, access to additional troubleshooting features for the HiveMQ Starter and Professional license lines, and numerous observability improvements and fixes.

Highlights

• New Mandatory Extension Start Designation
• More Features Added to HiveMQ Licence Suites

Specify an Extension as Mandatory for Startup

HiveMQ 4.40 introduces an optional start-mandatory flag in the hivemq-extension.xml file for extensions. When set to true for an enabled extension, this flag ensures that the HiveMQ broker can only start if the specified extension starts successfully. This is an effective mechanism to prevent your HiveMQ broker from starting until extensions that provide essential functionality for your use case have successfully started.

Starting with HiveMQ 4.40, the default setting of the start-mandatory flag of the HiveMQ Enterprise Security Extension is set to true. This default prevents your HiveMQ broker from starting when a faulty HiveMQ Enterprise Security Extension configuration is detected. For all other extensions, the default is false.

How it works

You can add a start-mandatory flag to the hivemq-extension.xml file of an extension to require the successful startup of the extension before the HiveMQ broker can start. When the flag is set to true, failure of the selected extension to start prevents the startup of your HiveMQ broker. If the flag is set to false or no start-mandatory configuration is present, the HiveMQ broker behavior remains the same as in previous versions (the faulty extension is disabled, and the broker startup continues).

TIP: This setting has no effect if an extension is disabled or if the extension is enabled/added at runtime.

<?xml version="1.0" encoding="UTF-8" ?>
<hivemq-extension>
    <id>hivemq-enterprise-security-extension</id>
    <version>4.40.0</version>
    <name>HiveMQ Enterprise Security Extension</name>
    <author>HiveMQ</author>
    <priority>1000</priority>
    <start-priority>1000</start-priority>
    <start-mandatory>true</start-mandatory>
</hivemq-extension>

For detailed configuration information, see our documentation.

How it helps

You can now specify whether the successful start of an extension is a mandatory part of your HiveMQ node startup process, based on your individual use case. If an enabled extension marked as mandatory does not start, the HiveMQ broker will not start. This feature allows you to protect your deployment from issues caused by faulty extension configuration changes. During a rolling upgrade, the process will halt at the surge node until the extension startup problem is resolved. This additional safeguard helps you maintain stability and consistency across your cluster.

More Features Available in Existing HiveMQ Licenses

Starting with HiveMQ 4.40, all HiveMQ suite licenses include more features designed to boost maintainability and troubleshooting: Dropped Messages View and Client Trace Recordings. These tools are now available with your existing suite license. If you are interested in load testing, contact our sales team to request access to HiveMQ Swarm. Additionally, all licenses in the HiveMQ Professional line now include cluster TLS to enable secure intracluster communication.

How it works

With the current release, HiveMQ Starter and Professional line license holders gain access to useful troubleshooting tools in the HiveMQ Control Center:

• Dropped Messages View to help identify why the HiveMQ Broker did not publish messages to the intended recipients.
• Trace Recordings to capture the MQTT packets passing through the broker to understand the behavior of specific clients or groups of clients.

Customers with Starter and Professional line licenses can now request a HiveMQ Swarm license to evaluate the scalability of their deployments.

Professional line license users also benefit from enhanced security with Cluster TLS, which enables secure communication between cluster nodes.

How it helps

The unlocked troubleshooting features help you pinpoint issues with clients connected to HiveMQ Broker. For example, analysis using the Dropped Messages page in the HiveMQ Control Center can reveal that the subscribers with persistent sessions are offline for prolonged periods, causing the queue of unconsumed messages to overflow, resulting in messages being dropped. Trace recordings provide deeper insights into the broker usage patterns of connected clients, such as finding attempts to subscribe to incorrect topic filters or publishing to topics for which there are no subscribers.

More Noteworthy Features and Improvements

HiveMQ Enterprise MQTT Broker

• Added metric to track open connections count per each TCP and Websocket listener with and without TLS.
• Removed a superfluous ERROR log statement during node shutdown to reduce unnecessary output.
• Fixed an issue that could log an unnecessary error when multiple nodes leave a cluster simultaneously.
• Fixed an issue that could cause a node to throw a NullPointerException (NPE) prematurely.
• Fixed a rare issue that could cause topology changes to stall when user-initiated Data Hub policy updates occur concurrently.

HiveMQ Enterprise Security Extension

• Set the start-mandatory flag for the extension to true to prevent broker startup when an invalid extension configuration is detected.
• Adjusted the extension startup procedure to remove the validation of connections to external sources such as SQL or LDAP servers from which the extension can potentially recover without a restart.
• Improved the connection parameters for the SQL realm.

HiveMQ Control Center v2

• Added the ability to configure a keystore for signing and validating JSON Web Tokens (JWT).

HiveMQ Health API

• Improved the Health API cluster component to signal a degraded state while nodes merge after a network partition.

IMPORTANT: Starting with the upcoming HiveMQ 4.40, the HiveMQ Platform will require glibc 2.17 or higher on Linux-based operating systems (except operating systems that use alternative implementations such as musl, e.g., Alpine Linux).

Most modern Linux distributions already meet this requirement. Only end-of-life (EOL) versions of Linux-based operating systems rely on older glibc versions. If you run an EOL OS, we strongly recommend updating to a supported distribution to reduce the risk of security vulnerabilities.

To check your system’s glibc version: Run the ldd --version command on your machine. Or, check your distribution details on distrowatch (for example, RedHat, Ubuntu, and OpenSUSE).

If you are on HiveMQ 4.28 LTS, no action is required. The LTS version meets the minimum required version of glibc 2.12.

Get Started Today

To upgrade to HiveMQ 4.40 from a previous HiveMQ version, follow our HiveMQ Upgrade Guide. To learn more about all the features the HiveMQ Platform offers, explore the HiveMQ User Guide.