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diff --git a/health/guides/vernemq/vernemq_mqtt_subscribe_error.md b/health/guides/vernemq/vernemq_mqtt_subscribe_error.md new file mode 100644 index 00000000..f14d18d5 --- /dev/null +++ b/health/guides/vernemq/vernemq_mqtt_subscribe_error.md @@ -0,0 +1,58 @@ +### Understand the alert + +This alert is related to `VerneMQ`, the open-source, distributed MQTT message broker. If you receive this alert, it means that the number of failed v3/v5 `SUBSCRIBE` operations has increased in the last minute. + +### What do v3 and v5 SUBSCRIBE operations mean? + +MQTT v3 and v5 are different versions of the MQTT protocol, used for the Internet of Things (IoT) devices and their communication. The `SUBSCRIBE` operation allows a client (device) to subscribe to a specific topic and receive messages published under that topic. + +### Troubleshoot the alert + +- Check the VerneMQ logs + +1. Identify the location of the VerneMQ logs. The default location is `/var/log/vernemq`. If you have changed the default location, you can find it in the `vernemq.conf` file by looking for `log.console.file` and `log.error.file`. + + ``` + grep log.console.file /etc/vernemq/vernemq.conf + grep log.error.file /etc/vernemq/vernemq.conf + ``` + +2. Analyze the logs for any errors or issues related to the `SUBSCRIBE` operation: + + ``` + tail -f /path/to/vernemq/logs + ``` + +- Check the system resources + +1. Check the available resources (RAM and CPU) on your system: + + ``` + top + ``` + +2. If you find that the system resources are low, consider adding more resources or stopping unnecessary processes/applications. + +- Check the client-side logs + +1. Most MQTT clients (e.g., Mosquitto, Paho, MQTT.js) provide their logs to help you identify any issues related to the `SUBSCRIBE` operation. + +2. Analyze the client logs for errors in connecting, subscribing, or receiving messages from the MQTT broker. + +- Analyze the topics and subscriptions + +1. Verify if there are any invalid, restricted, or forbidden topics in your MQTT broker. + +2. Check the ACLs (Access Control Lists) and client authentication settings in your VerneMQ `vernemq.conf` file. + + ``` + grep -E '^(allow_anonymous|vmq_acl.acl_file|vmq_passwd.password_file)' /etc/vernemq/vernemq.conf + ``` + +3. Ensure the `ACLs` and authentication configuration are correct and allow the clients to subscribe to the required topics. + +### Useful resources + +1. [VerneMQ Administration](https://vernemq.com/docs/administration/) +2. [VerneMQ Configuration](https://vernemq.com/docs/configuration/) +3. [VerneMQ Logging](https://vernemq.com/docs/guide/internals.html#logging)
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