EMQX Cluster Nodes Not Connecting

In this tutorial, you'll learn about EMQX Cluster Nodes Not Connecting. We cover key concepts, practical examples, and best practices.

The Problem

EMQX nodes cannot form a cluster across multiple servers.

Quick Fix

Wrong

emqx_ctl cluster join emqx2@192.168.1.2  # Node not reachable

Join fails — node not reachable or cookie mismatch.

Right

# 1. Check node cookie (must match on all nodes)
sudo cat /etc/emqx/emqx.conf | grep cookie
# 2. Set cookie explicitly
# node.cookie = 'mysecrectcookie'

# 3. Ensure ports are open
sudo ufw allow 4370  # EPMD
sudo ufw allow 5370  # Cluster communication

# 4. Join cluster (on one node)
emqx_ctl cluster join emqx@node2.example.com

# 5. Verify
emqx_ctl cluster status

Cluster status: 2 nodes running.

Prevention

All nodes must use the same cookie. Open firewall ports 4370 (EPMD) and 5370 (cluster). Nodes should have synchronized clocks (NTP). Use static cluster or DNS-based discovery for auto-clustering. EMQX Enterprise supports multi-datacenter replication.

DodaTech engineers apply these same patterns across Doda Browser, DodaZIP, and Durga Antivirus Pro for production IoT reliability.

FAQ