OpsCenter agent can't connect to node, returns "TransportException: [/127.0.0.1:9042] Cannot connect"

Question

Can't connect to Cassandra (All host(s) tried for query failed (tried: /127.0.0.1:9042 (com.datastax.driver.core.exceptions.TransportException: [/127.0.0.1:9042] Cannot connect))), retrying soon.

on Opscenter log

ERROR: Alert for agents with issues on node 192.168.211.2 is currently Fired (MainThread)

on node agent.log

 INFO [async-dispatch-6] 2023-03-27 09:43:38,279 Starting 
 monitored database connection.
 ERROR [async-dispatch-6] 2023-03-27 09:43:40,490 Can't connect 
 to Cassandra (All host(s) tried for query failed (tried: 
 /127.0.0.1:9042 
 (com.datastax.driver.core.exceptions.TransportException: 
 [/127.0.0.1:9042] Cannot connect))), retrying soon.

 

Answer 1

what's the version of DataStax Enterprise (DSE) & OpsCenter being used here in this setup? I assume you're using compatible product versions here.

Also, you may want to ensure you're setting up opscenterd.conf (on the OpsCenter machine), address.yaml (on the DSE node itself) correctly with the correct IPs to use. If you've already followed all the set up instructions from here and if you've a valid DSE subscription license, you may create a support ticket DataStax Support portal by uploading opscenterd.conf, opscenterd.log, address.yaml, agent.log, cassandra.yaml, and dse.yaml to get started with the triage.

Answer 2

It appears as though you have misconfigured the agent on the node so it cannot connect to the local Cassandra instance.

This error indicates that you've configured the agent to connect to localhost:

ERROR [async-dispatch-6] 2023-03-27 09:43:40,490 Can't connect 
 to Cassandra (All host(s) tried for query failed (tried: 
 /127.0.0.1:9042 
 (com.datastax.driver.core.exceptions.TransportException: 
 [/127.0.0.1:9042] Cannot connect))), retrying soon.

Connecting to 127.0.0.1 is a mistake because it doesn't make sense for a DSE node to be listening for client connections on localhost. It needs to be set to the same IP as the native_transport_address in cassandra.yaml.

If you've manually configured the address.yaml for the agent, review it particularly for the hosts property which should NOT be set to 127.0.0.1. We recommend that you let OpsCenter automatically configure the agents. Cheers!