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Debugging KAFKA connectivity integration with Remote Application including Spring Boot, Spark, Console Consumer, Open SSL

By Dinesh

 

Our downstream partners wanted to consume data from Kafka Topic. They did open network & firewall ports with respective zookeeper & broker servers.

But, Spring Boot application or Console Consumer failed to consume messages from Kafka topic. Refer log stack trace below - 

[2024-01-10 13:33:34,759] DEBUG [Consumer clientId=consumer-o2_prism_group-1, groupId=o2_prism_group] Node -1 disconnected. (org.apache.kafka.clients.NetworkClient)

[2024-01-10 13:33:34,762] WARN [Consumer clientId=consumer-o2_prism_group-1, groupId=o2_prism_group] Bootstrap broker ncxxx001.h.c.com:9093 (id: -1 rack: null) disconnected (org.apache.kafka.clients.NetworkClient)

[2024-01-10 13:33:34,860] DEBUG [Consumer clientId=consumer-o2_prism_group-1, groupId=o2_prism_group] Initialize connection to node ncxxx001.h.c.com:9093 (id: -1 rack: null) for sending metadata request (org.apache.kafka.clients.NetworkClient)

[2024-01-10 13:33:34,861] DEBUG [Consumer clientId=consumer-o2_prism_group-1, groupId=o2_prism_group] Initiating connection to node ncxxx001.h.c.com:9093 (id: -1 rack: null) using address ncxxx001.h.c.com/192.168.32.1 (org.apache.kafka.clients.NetworkClient)

Using SSLEngineImpl.


We have security.protocol=sasl_ssl . There are 2 parts to debugging process - 

First SASL ( Kerberos )

- Set following property to enable Kerberos debugging logs 

  • -Dsun.security.krb5.debug=true
- This property should help us debug - If KDC Server  is accessible & it is generating valid KRB5 ticket for the application.


Second SSL

- Set following property to enable SSL debugging logs 
  • -Djavax.net.debug=ssl
- SSL-Handshake (One Way) mainly consists of the following steps –
  1. *** ClientHello, TLSv1.2
  2. *** ServerHello, TLSv1.2
  3. *** Certificate chain
  4. *** ECDH ServerKeyExchange
  5. *** ServerHelloDone
  6. *** ECDHClientKeyExchange
  7. *** Finished  [Notifying client-side handshake finished]
  8. *** Finished  [Notifying server-side handshake finished]


We figured out that, We are not able to read Acknowledgment of Client Hello that came from server for step #1 above.

To further debug this, 
  • One can use tcpdump to listen to network. For example, below command will listen to tun0 ethernet connection and save data to file ti-dump.pcap - 
    •  sudo tcpdump -i tun0 -w ti-dump.pcap
  • Now, one can install Wireshark to analyze tcpdump file.


This can help debug where packets are being lost. Reference - https://youtu.be/QTHCNeyhPYM?si=V2eaWgcOS5ib1faa

Many a times packets may drop because of content filtering, which might not show up here exactly. 

Other reason for failure can be Server terminated TLS handshake because matching Cipher was not found. But, one should see that in tcpdump.

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