MQTT 5 broker (EMQX) - AWS IoT Greengrass

MQTT 5 broker (EMQX)

The EMQX MQTT broker component (aws.greengrass.clientdevices.mqtt.EMQX) handles MQTT messages between client devices and a Greengrass core device. This component provides a modified version of the EMQX MQTT 5.0 broker. Deploy this MQTT broker to use MQTT 5 features in communication between client devices and a core device. For more information about how to choose an MQTT broker, see Choose an MQTT broker.

This broker implements the MQTT 5.0 protocol. It includes support for session and message expiration intervals, user properties, shared subscriptions, topic aliases, and more. MQTT 5 is backwards compatible with MQTT 3.1.1, so if you run the Moquette MQTT 3.1.1 broker, you can replace it with the EMQX MQTT 5 broker, and client devices can continue to connect and operate as usual.

MQTT 5 features are limited to communication between core devices and client devices, because the AWS IoT Core MQTT broker implements the MQTT 3.1.1 protocol. As a result, when you use the MQTT bridge component to relay MQTT messages between AWS IoT Core and this MQTT 5 broker, messages use MQTT 3.1.1 instead of MQTT 5.

Note

Client devices are local IoT devices that connect to a Greengrass core device to send MQTT messages and data to process. For more information, see Interact with local IoT devices.

Versions

This component has the following versions:

  • 1.0.x

Type

This component is a generic component (aws.greengrass.generic). The Greengrass nucleus runs the component's lifecycle scripts.

For more information, see Component types.

Operating system

This component can be installed on core devices that run the following operating systems:

  • Linux

  • Windows

Requirements

This component has the following requirements:

  • The core device must be able to accept connections on the port where the MQTT broker operates. This component runs the MQTT broker on port 8883 by default. You can specify a different port when you configure this component.

    If you specify a different port, and you use the MQTT bridge component to relay MQTT messages to other brokers, you must use MQTT bridge v2.1.0 or later. Configure it to use the port where the MQTT broker operates.

    If you specify a different port, and you use the IP detector component to manage MQTT broker endpoints, you must use IP detector v2.1.0 or later. Configure it to report the port where the MQTT broker operates.

  • On Linux core devices, Docker installed and configured on the core device:

    • Docker Engine 1.9.1 or later installed on the Greengrass core device. Version 20.10 is the latest version that is verified to work with the AWS IoT Greengrass Core software. You must install Docker directly on the core device before you deploy components that run Docker containers.

    • The Docker daemon started and running on the core device before you deploy this component.

    • The system user that runs this component must have root or administrator permissions. Alternatively, you can run this component as a system user in the docker group and configure this component's requiresPrivileges option to false to run the EQMX MQTT broker without privileges.

Dependencies

When you deploy a component, AWS IoT Greengrass also deploys compatible versions of its dependencies. This means that you must meet the requirements for the component and all of its dependencies to successfully deploy the component. This section lists the dependencies for the released versions of this component and the semantic version constraints that define the component versions for each dependency. You can also view the dependencies for each version of the component in the AWS IoT Greengrass console. On the component details page, look for the Dependencies list.

The following table lists the dependencies for version 2.0.0 of this component.

Dependency Compatible versions Dependency type
Client device auth >=2.2.0 <2.3.0 Hard

For more information about component dependencies, see the component recipe reference.

Configuration

This component provides the following configuration parameters that you can customize when you deploy the component.

emqx

(Optional) The EMQX MQTT broker configuration to use. You can configure a subset of EMQX configuration options in this component.

This object contains the following information:

listener.ssl.external

(Optional) The port where the MQTT broker operates.

Note

If you specify a different port, and you use the MQTT bridge component to relay MQTT messages to other brokers, you must use MQTT bridge v2.1.0 or later. Configure it to use the port where the MQTT broker operates.

If you specify a different port, and you use the IP detector component to manage MQTT broker endpoints, you must use IP detector v2.1.0 or later. Configure it to report the port where the MQTT broker operates.

Default: 8883

listener.ssl.external.max_connections

(Optional) The maximum number of concurrent connections that the MQTT broker supports.

Default: 1024000

listener.ssl.external.max_conn_rate

(Optional) The maximum number of new connections per second the MQTT broker can receive.

Default: 500

listener.ssl.external.rate_limit

(Optional) The bandwidth limit for all connections to the MQTT broker. Specify the bandwidth and duration for that bandwidth separated by a comma (,) in the following format: bandwidth,duration. For example, you can specify 50KB,5s to limit the MQTT broker to 50 kilobytes (KB) of data every 5 seconds.

listener.ssl.external.handshake_timeout

(Optional) The amount of time that the MQTT broker waits to finish authenticating a new connection.

Default: 15s

mqtt.max_packet_size

(Optional) The maximum size of an MQTT message.

Default: 268435455 (256 MB minus 1)

log.level

(Optional) The log level for the MQTT broker. Choose from the following options:

  • debug

  • info

  • notice

  • warning

  • error

  • critical

  • alert

  • emergency

The default log level is warning.

requiresPrivilege

(Optional) On Linux core devices, you can specify to run the EMQX MQTT broker without root or administrator privileges. If you set this option to false, the system user that runs this component must be a member of the docker group.

Default: true

startupTimeoutSeconds

(Optional) The maximum of time in seconds for the EMQX MQTT broker to start. The component's state changes to BROKEN if it exceeds this timeout.

Default: 90

ipcTimeoutSeconds

(Optional) The maximum of time in seconds for the component to wait for the Greengrass nucleus to respond to interprocess communication (IPC) requests. Increase this number if this component reports timeout errors when it checks if a client device is authorized.

Default: 5

crtLogLevel

(Optional) The log level for the AWS Common Runtime (CRT) library.

Defaults to the EMQX MQTT broker log level (log.level in emqx).

restartIdentifier

(Optional) Configure this option to restart the EMQX MQTT broker. When this configuration value changes, this component restarts the MQTT broker. You can use this option to force client devices to disconnect.

Example: Configuration merge update

The following example configuration specifies to operate the MQTT broker on port 443.

{ "emqx": { "listener.ssl.external": "8883", "listener.ssl.external.max_connections": "1024000", "listener.ssl.external.max_conn_rate": "500", "listener.ssl.external.rate_limit": "50KB,5s", "listener.ssl.external.handshake_timeout": "15s", "log.level": "warning" }, "requiresPrivilege": "true", "startupTimeoutSeconds": "90", "ipcTimeoutSeconds": "5" }

Local log file

This component uses the following log file.

Linux
/greengrass/v2/logs/aws.greengrass.clientdevices.mqtt.EMQX.log
Windows
C:\greengrass\v2\logs\aws.greengrass.clientdevices.mqtt.EMQX.log

To view this component's logs

  • Run the following command on the core device to view this component's log file in real time. Replace /greengrass/v2 or C:\greengrass\v2 with the path to the AWS IoT Greengrass root folder.

    Linux
    sudo tail -f /greengrass/v2/logs/aws.greengrass.clientdevices.mqtt.EMQX.log
    Windows (PowerShell)
    Get-Content C:\greengrass\v2\logs\aws.greengrass.clientdevices.mqtt.EMQX.log -Tail 10 -Wait

Licenses

On Windows operating systems, this software includes code distributed under the Microsoft Software License Terms - Microsoft Visual Studio Community 2022. By downloading this software, you agree to that code's license terms.

This component is released under the Greengrass Core Software License Agreement.

Changelog

The following table describes the changes in each version of the component.

Version

Changes

1.0.0

Initial version.