Pre-flight Interface cannot see Datanode

Graylog Central (peer support)
1

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1. Describe your incident:
New Install for two Nodes on Ubuntu. Bring up Preflight Interface and cannot see the Datanode

2. Describe your environment:

  • OS Information: Ubuntu 22.04 LTS and Ubuntu 24.04 LTS (this being an act of futility). Mongo/Graylog on one. Datanode on the other. Running on VMware 7.0.3

  • Package Version: 6.1.10

  • Service logs, configurations, and environment variables:
    Can’t attach logs because I am a new user.

3. What steps have you already taken to try and solve the problem?

A. Looked at the logs and can see both Server and Datanode at connecting to Mongo.
B. Used netstat to confirm connections.
C. Datanode has port 8999 open, but port 9200 stays close. I assume because there is no certificate
D. Server has port 9000 open and connecting. I can log in on Preflight interface, but no data nodes

4. How can the community help?
I don’t understand how the preflight interface knows a datanode has registered. Looking at the datanode log, it appears that the datanode registers in the mongodb and the preflight interface finds it. Is this correct?

If this is true, and I have no knowledge of mongo, is there something wrong with mongo or at least the database? How do I troubleshoot this?

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2

The way graylog “finds” the datanode is that datanode writes its publish uri into the mongoDB. Its a pretty good bet that the problem lies in the connection to mongo somehow. Are they both pointed to the same mongo service with the same database name, and do they both havr the exact same password secret set in datanode.conf and server.conf?

3

Joel, thanks. That is what I had deduced.

Like I said I know a lot, bit mongo is not one of those things. Networks and Linux: yes.

I have attached a PDF with screen shots of netstat from both nodes showing connections. So I really don’t think it is a network problem.

In the mongod.log, I can see both nodes connect to the mongod. However, I do see with record about conn5 (127.0.0.1) that something hiccupped. Here is a snippet of what the mongod.log shows:

{“t”:{“$date”:“2025-04-16T18:36:10.220-04:00”},“s”:“I”, “c”:“NETWORK”, “id”:51800, “ctx”:“conn5”,“msg”:“client metadata”,“attr”:{“remote”:“127.0.0.1:34038”,“client”:“conn5”,“negotiatedCompressors”:,“doc”:{“driver”:{“name”:“mongo-java-driver|legacy”,“version”:“5.2.0”},“os”:{“type”:“Linux”,“name”:“Linux”,“architecture”:“amd64”,“version”:“6.8.0-57-generic”},“platform”:“Java/Eclipse Adoptium/17.0.14+7”}}}
{“t”:{“$date”:“2025-04-16T18:36:10.236-04:00”},“s”:“I”, “c”:“NETWORK”, “id”:22943, “ctx”:“listener”,“msg”:“Connection accepted”,“attr”:{“remote”:“127.0.0.1:34048”,“uuid”:{“uuid”:{“$uuid”:“63fb8940-a2d1-49b5-8053-39a5ce59ea56”}},“connectionId”:6,“connectionCount”:6}}
{“t”:{“$date”:“2025-04-16T18:36:10.237-04:00”},“s”:“I”, “c”:“NETWORK”, “id”:51800, “ctx”:“conn6”,“msg”:“client metadata”,“attr”:{“remote”:“127.0.0.1:34048”,“client”:“conn6”,“negotiatedCompressors”:,“doc”:{“driver”:{“name”:“mongo-java-driver|legacy”,“version”:“5.2.0”},“os”:{“type”:“Linux”,“name”:“Linux”,“architecture”:“amd64”,“version”:“6.8.0-57-generic”},“platform”:“Java/Eclipse Adoptium/17.0.14+7”}}}
{“t”:{“$date”:“2025-04-16T18:36:10.244-04:00”},“s”:“I”, “c”:“NETWORK”, “id”:22943, “ctx”:“listener”,“msg”:“Connection accepted”,“attr”:{“remote”:“127.0.0.1:34056”,“uuid”:{“uuid”:{“$uuid”:“49a667a2-f87b-4276-815d-444ac3e734c4”}},“connectionId”:7,“connectionCount”:7}}
{“t”:{“$date”:“2025-04-16T18:36:10.244-04:00”},“s”:“I”, “c”:“NETWORK”, “id”:51800, “ctx”:“conn7”,“msg”:“client metadata”,“attr”:{“remote”:“127.0.0.1:34056”,“client”:“conn7”,“negotiatedCompressors”:,“doc”:{“driver”:{“name”:“mongo-java-driver|legacy”,“version”:“5.2.0”},“os”:{“type”:“Linux”,“name”:“Linux”,“architecture”:“amd64”,“version”:“6.8.0-57-generic”},“platform”:“Java/Eclipse Adoptium/17.0.14+7”}}}
{“t”:{“$date”:“2025-04-16T18:36:10.262-04:00”},“s”:“I”, “c”:“NETWORK”, “id”:6788700, “ctx”:“conn7”,“msg”:“Received first command on ingress connection since session start or auth handshake”,“attr”:{“elapsedMillis”:18}}
{“t”:{“$date”:“2025-04-16T18:36:10.290-04:00”},“s”:“I”, “c”:“-”, “id”:20883, “ctx”:“conn5”,“msg”:“Interrupted operation as its client disconnected”,“attr”:{“opId”:101}}
{“t”:{“$date”:“2025-04-16T18:36:10.301-04:00”},“s”:“I”, “c”:“NETWORK”, “id”:22944, “ctx”:“conn6”,“msg”:“Connection ended”,“attr”:{“remote”:“127.0.0.1:34048”,“uuid”:{“uuid”:{“$uuid”:“63fb8940-a2d1-49b5-8053-39a5ce59ea56”}},“connectionId”:6,“connectionCount”:6}}
{“t”:{“$date”:“2025-04-16T18:36:10.302-04:00”},“s”:“I”, “c”:“NETWORK”, “id”:22944, “ctx”:“conn7”,“msg”:“Connection ended”,“attr”:{“remote”:“127.0.0.1:34056”,“uuid”:{“uuid”:{“$uuid”:“49a667a2-f87b-4276-815d-444ac3e734c4”}},“connectionId”:7,“connectionCount”:5}}
{“t”:{“$date”:“2025-04-16T18:36:10.317-04:00”},“s”:“I”, “c”:“NETWORK”, “id”:22944, “ctx”:“conn5”,“msg”:“Connection ended”,“attr”:{“remote”:“127.0.0.1:34038”,“uuid”:{“uuid”:{“$uuid”:“d463154e-73b1-40fa-973d-ae96c1cd42ed”}},“connectionId”:5,“connectionCount”:4}}

I am pretty sure the password and like are all ok, since there is communications. However I really don’t know how to read the log.

Thanks for your help.

Bob

4

What does the datanode.log say? I can’t see the PDF you attached, but the connections in this log are all from localhost, not your remote datanode.

Have you ensured that your MongoDB instance is configured to listen on an external interface and that the connection string on your datanode is correctly configured?