Running Snowplow on AWS MSK (Amazon Managed Streaming for Apache Kafka) is a powerful way to handle event data pipelines at scale. However, setting up a secure connection between Snowplow's collector and Kafka brokers can sometimes lead to authentication issues.

A Snowplow user recently reported encountering an error during authentication while using AWS MSK with Snowplow’s Scala Stream Collector. Below, we’ll walk through the issue, diagnosis, and solution — to help you get your Snowplow collector reliably streaming to Kafka.

Q: What is the authentication error encountered when running Snowplow with AWS MSK?

When starting the Snowplow Scala Stream Collector, the following warning appeared:

[kafka-producer-network-thread | producer-1] WARN org.apache.kafka.clients.NetworkClient - [Producer clientId=producer-1] Connection to node -1 (MYCLUSTERHOST.kafka.us-east-1.amazonaws.com/10.44.1.27:9096) terminated during authentication. This may happen due to any of the following reasons: 

(1) Authentication failed due to invalid credentials with brokers older than 1.0.0, 

(2) Firewall blocking Kafka TLS traffic (e.g., it may only allow HTTPS traffic), 

(3) Transient network issue.

Despite network connectivity tests succeeding (e.g., via nc -zv), the connection terminated during authentication.

Q: What Snowplow configuration was used?

Here’s the relevant Kafka sink configuration from the collector:

sink {

  enabled = kafka

  brokers = "MYCLUSTERHOST.kafka.us-east-1.amazonaws.com:9096"

  retries = 0

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  producerConf {

    "sasl.jaas.config" = "org.apache.kafka.common.security.plain.PlainLoginModule required username='myuser' password='mypassword';"

    "security.protocol" = "SASL_SSL"

    "sasl.mechanism" = "SCRAM-SHA-512"

  }

}

• Security protocol: SASL_SSL
  
  
• SASL mechanism: SCRAM-SHA-512
  
  

The brokers property points to the AWS MSK bootstrap broker.

Q: What are the most common causes of this authentication error?

This specific Kafka authentication error typically results from:

• Mismatched SASL mechanism between client and server.
  
  
• Incorrect or missing credentials.
  
  
• Firewall or VPC networking issues, particularly when dealing with TLS traffic.
  
  
• Brokers misconfigured for expected authentication mechanisms (e.g., the broker is expecting IAM authentication or a different SASL mechanism).
  
  

Important: While basic connectivity (nc, telnet) shows the port is open, it does not verify protocol-level compatibility.

Q: How can I resolve the Kafka authentication error with Snowplow and AWS MSK?

Here’s a proven checklist to debug and solve the issue:

1. Confirm Broker Authentication Type

AWS MSK supports several authentication methods:

• TLS (default)
  
  
• SASL/SCRAM (SASL_SSL)
  
  
• IAM Authentication
  
  

✅ Solution: Ensure your MSK cluster is configured to use SASL/SCRAM authentication (not just TLS or IAM).
You can verify this in the AWS Console → MSK Cluster → Client Authentication settings.

Tip: If your MSK cluster was provisioned with only TLS authentication, you must update the cluster or create a new one with SASL/SCRAM enabled.

2. Check Snowplow's SASL Mechanism

The Snowplow collector is configured for "sasl.mechanism" = "SCRAM-SHA-512".
✅ Solution: Make sure your AWS MSK cluster also uses SCRAM-SHA-512, not SCRAM-SHA-256.

Note: SCRAM-SHA-512 provides stronger security than SCRAM-SHA-256 but must match exactly between client and server.

3. Validate the Credentials

If the credentials (username and password) are wrong or expired, authentication will fail.

✅ Solution:

• Verify the Kafka username and password.
  
  
• Confirm the secret values if using AWS Secrets Manager.
  
  
• Double-check the spelling and case sensitivity.
  
  

4. Verify MSK Broker Listeners

AWS MSK provides different broker endpoints based on the authentication method:

• b-1.cluster-name.kafka.us-east-1.amazonaws.com:9094 (for TLS)
  
  
• b-1.cluster-name.kafka.us-east-1.amazonaws.com:9096 (for SASL/SCRAM)
  
  

✅ Solution: Use the correct port :9096 for SASL/SCRAM with Snowplow, as shown in the user’s config.

5. Update Collector and Kafka Client Versions

Older versions of Kafka clients may not handle SASL/SCRAM consistently.

✅ Solution:

• Use the latest stable release of the Snowplow Scala Stream Collector.
  
  
• Ensure the Kafka client library bundled supports your authentication method.
  
  

Q: Is there an updated recommended way to configure Snowplow for AWS MSK?

Yes. As of 2024-2025, Snowplow recommends:

• Running collectors in a VPC with PrivateLink if using AWS MSK (for added security).
  
  
• Managing Kafka credentials securely using AWS Secrets Manager or environment variables, not hardcoding.
  
  
• Setting "acks" = "all" in the Kafka producer config for better delivery guarantees.
  
  
• Monitoring producer metrics via Snowplow Iglu Central metrics schemas.
  
  

Example updated producerConf block:

producerConf {

  "sasl.jaas.config" = ${?KAFKA_SASL_JAAS_CONFIG}

  "security.protocol" = "SASL_SSL"

  "sasl.mechanism" = "SCRAM-SHA-512"

  "acks" = "all"

}

Where KAFKA_SASL_JAAS_CONFIG is an environment variable containing:

org.apache.kafka.common.security.plain.PlainLoginModule required username='myuser' password='mypassword';

This improves security and aligns with AWS best practices.

Final Thoughts

Running Snowplow on AWS MSK offers a powerful, scalable, secure pipeline for event data collection. However, careful alignment of authentication settings between Snowplow and Kafka brokers is critical for a successful deployment.

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