Etcd Cluster Discovery Extension

Extension Type: Integration

Version: 0.1

License: Apache License 2.0

Purpose

This HiveMQ extension allows your HiveMQ cluster nodes to discover each other dynamically by regularly exchanging their information via etcd.

HiveMQ instances are added at runtime as soon as they become available by placing their information, on how to connect to them, to the configured key. The extension will regularly check the configured etcd key for files from other HiveMQ nodes. Additionally every broker updates its own entry on a regular basis to prevent the entry from expiring.

Installation

• Download the extension from GitHub’s release page.

• Copy the content of the zip file to the extensions folder of your HiveMQ nodes.

• Modify the etcdDiscovery.properties file for your needs or set environment variables

• Change the discovery mechanism of HiveMQ to extension.

Configuration

The information each node writes into etcd consists of an ip-address and a port. The ip-address and port are taken from the external-address and external-port which is configured in the cluster transport (config.xml). If they are not set, the bind-address and bind-port will be used.

The etcdDiscovery.properties can be reloaded during runtime.

Configuration from etcdDiscovery.properties will always take precedent over environment variables.

General Configuration

Config name	Environment	Required	Description
key	HIVEMQ_ETCD_KEY		Key to store discovery entries at
etcd-endpoint	HIVEMQ_ETCD_ENDPOINT	x	The region in which this S3 bucket resides. (List of regions: {s3_regions}[AWS documentation^])
etcd-port	HIVEMQ_ETCD_PORT		etcd port to connect at
expiration	HIVEMQ_ETCD_EXPIRATION		Time in seconds after which an entry in etcd is considered expired
update-interval	HIVEMQ_ETCD_UPDATE_INTERVAL		Time in seconds after which an entry in etcd is refreshed (Must be smaller than file-expiration)
use-tls	HIVEMQ_ETCD_USE_TLS		Use TLS for connection to etcd
ca-path	HIVEMQ_ETCD_CA_PATH		Certificate authority to use for validating tls connection to etcd - if not set, system certificates will be used

Default Configuration

key=/hivemq/discovery
etcd-endpoint=
etcd-port=2379
expiration=360
update-interval=180
use-tls=false
ca-path=