Kafka (Writing)

Customers on a paid plan can enable direct access via Proxy.

This guide shows you how to write messages to your Streamkap Kafka topics using Python or command-line tools.

Creating Kafka Users

You can create and manage Kafka users through the Streamkap web interface at Kafka Access. To create a new Kafka user, click the “Create User” button. This will open the user creation dialog where you can configure the user’s permissions and access settings.

For detailed step-by-step instructions on creating and managing Kafka users through the UI, see the Kafka Access documentation.

User Configuration

When creating a Kafka user, you’ll need to configure:

Username: Enter a lowercase username for the Kafka user
Password: Set a secure password for authentication
Whitelisted IPs: Specify IP addresses or CIDR ranges that are allowed to connect
Kafka ACLs: Configure access control lists to define what the user can do

Access Control Lists (ACLs)

Kafka ACLs control what operations users can perform on specific resources. When creating a user, you can configure:

Resource Type:
- TOPIC - Controls access to Kafka topics
- GROUP - Controls access to consumer groups
Operation: The type of operation allowed (varies by resource type)
For TOPIC resources:
- ALL - All operations
- WRITE - Write/produce messages
- READ - Read/consume messages
- ALTER - Modify resource configurations
- ALTER_CONFIGS - Modify resource configurations
- CREATE - Create new resources
- DELETE - Delete resources
- DESCRIBE - View resource metadata
- DESCRIBE_CONFIGS - View resource configurations For GROUP resources (consumers only):
- READ - Join and consume from consumer group
- DELETE - Delete consumer group
- DESCRIBE - View consumer group metadata
Pattern Type: How the resource name is matched
- LITERAL - Exact match of the resource name
- PREFIXED - Match resources with the specified prefix
Name: The specific resource name or prefix to apply the ACL to

Connection Details

Once a user is created, your endpoints are shown under “Proxy Endpoints”. These endpoints follow the naming pattern: <service-name>-<kafka-username>.streamkap.net:PORT Where:

<service-name> - Your Streamkap service/tenant name
<kafka-username> - The Kafka user’s username
PORT - One of the available ports: 32400, 32401, or 32402

Example proxy endpoints:

my-service-kafka-user.streamkap.net:32400
my-service-kafka-user.streamkap.net:32401
my-service-kafka-user.streamkap.net:32402

Connection settings:

Security protocol: SASL_SSL (recommended for secure connections)
SASL mechanism: PLAIN
Username/password: As configured for the user

Required Permissions

To write to Kafka topics, your user needs these ACL permissions: Essential permissions (always required):

Resource Type: TOPIC | Operation: WRITE | Pattern Type: LITERAL or PREFIXED | Name: Your topic name/prefix
Resource Type: TOPIC | Operation: DESCRIBE | Pattern Type: LITERAL or PREFIXED | Name: Your topic name/prefix

Additional permission (if topic doesn’t exist):

Resource Type: TOPIC | Operation: CREATE | Pattern Type: LITERAL or PREFIXED | Name: Your topic name/prefix

Both WRITE and DESCRIBE are required for successful message production. Add CREATE only if you need to create new topics.

Code Examples

Prerequisites

Python
CLI

Install the required packages:

pip install confluent-kafka certifi

from confluent_kafka import Producer
import socket
import certifi
import os

def delivery_report(err, msg):
    """Called once for each message produced to indicate delivery result."""
    if err is not None:
        print(f'Message delivery failed: {err}')
    else:
        print(f'Message delivered to {msg.topic()} [{msg.partition()}] at offset {msg.offset()}')

conf = {
    'bootstrap.servers': '<service-name>-<kafka-username>.streamkap.net:32400,<service-name>-<kafka-username>.streamkap.net:32401,<service-name>-<kafka-username>.streamkap.net:32402',
    'security.protocol': 'SASL_SSL',
    'sasl.mechanism': 'PLAIN',
    'sasl.username': '<your-username>',
    'sasl.password': '<your-password>',
    'client.id': socket.gethostname(),
    # Required to trust AWS root certificates
    'ssl.ca.location': certifi.where(),
}

producer = Producer(conf)

# Produce a message
producer.produce('<topic-name>', key='key1', value='Hello Streamkap!', callback=delivery_report)
producer.flush()

# Note: If the topic doesn't exist, you may need to create it first
# This requires CREATE permissions in addition to WRITE and DESCRIBE

Replace the following values in the examples above:

Your proxy endpoints are listed in the Streamkap web interface at Kafka Access under “Proxy Endpoints”. The format is <service-name>-<kafka-username>.streamkap.net:PORT.

<service-name>-<kafka-username> - Your proxy endpoints
<your-username> - Your Kafka user username
<your-password> - Your Kafka user password
<topic-name> - The topic you want to write to

Troubleshooting

Connectivity Issues

Before diving into complex debugging, verify basic network connectivity to your Streamkap Kafka cluster.Test DNS Resolution:

# Check if hostname resolves
nslookup <service-name>-<kafka-username>.streamkap.net

Test Port Connectivity:

# Test with netcat (preferred - quick and clean)
nc -zv <service-name>-<kafka-username>.streamkap.net 32400

# Test all three ports
nc -zv <service-name>-<kafka-username>.streamkap.net 32400
nc -zv <service-name>-<kafka-username>.streamkap.net 32401
nc -zv <service-name>-<kafka-username>.streamkap.net 32402

# Alternative with telnet (press Ctrl+C to exit after connection success)
telnet <service-name>-<kafka-username>.streamkap.net 32400

Test SSL/TLS Handshake:

# Test SSL handshake and certificate chain
openssl s_client -connect <service-name>-<kafka-username>.streamkap.net:32400 -servername <service-name>-<kafka-username>.streamkap.net

# Alternative with timeout (press Ctrl+C to exit)
echo "Q" | openssl s_client -connect <service-name>-<kafka-username>.streamkap.net:32400 -servername <service-name>-<kafka-username>.streamkap.net

Common Network Issues & Solutions:

VPN interference: Disconnect VPN and try again
Firewall blocking ports: Ensure ports 32400-32402 are accessible
Whitelisted IPs: Verify your public IP address is in the user’s whitelist

If basic connectivity fails, check your network configuration before proceeding with Kafka-specific troubleshooting.

SSL & Authentication Issues

Common Errors:

SSL connection closed by peer during message production
SSL certificate verification failures
SASL authentication failed or authentication errors
SSL handshake failures

Authentication Solutions:

Verify username and password are correct
Ensure sasl.mechanism is set to PLAIN and security.protocol is set to SASL_SSL
Check that the user account is active and not disabled
Confirm the user has basic connection permissions

SSL Solutions:

For Python
Ensure certificates are properly configured:

pip install --upgrade certifi

import certifi
'ssl.ca.location': certifi.where()

For CLI tools
Try different certificate paths:

-X ssl.ca.location=/etc/ssl/cert.pem
# or
-X ssl.ca.location=/etc/ssl/certs/ca-certificates.crt

Disable hostname verification (temporary):
```
'ssl.endpoint.identification.algorithm': 'none'
```
Contact support if issues persist - may require infrastructure team resolution

Note: Metadata operations (listing topics) may work while data operations fail

Topic authorization failed

Error: Topic authorization failed or TOPIC_AUTHORIZATION_FAILEDCause: Missing TOPIC READ or TOPIC WRITE permissionsSolution: Add the appropriate ACL permissions:

Resource Type: TOPIC
Operation: READ (for consumers) or WRITE (for producers)
Pattern Type: LITERAL or PREFIXED
Name: Your topic name or prefix

Group authorization failed (consumers only)

Error: GROUP_AUTHORIZATION_FAILED or Group authorization failedCause: Missing GROUP READ permissions for your consumer groupSolution: Add the following ACL permission:

Resource Type: GROUP
Operation: READ
Pattern Type: LITERAL or PREFIXED
Name: Your consumer group ID (e.g., my-consumer-group)

Note: This only affects Python consumers and CLI tools using consumer groups

No messages received (consumers only)

Issue: Consumer polls but receives no messagesPossible Causes:

No messages in topic: Topic is empty or messages are at different offsets
Consumer group offset: Group has already consumed available messages
Partition assignment: Messages might be in different partitions
Offset reset: Check auto.offset.reset setting

Solutions:

Check topic contents: Use CLI to verify messages exist
Use fresh consumer group: Try with a new group.id
Reset offsets: Set auto.offset.reset to earliest
Check all partitions: For CLI, try without specifying partition

Getting Started

App

Deployment

Sources

Destinations

Transformation

Billing

Security

Rest API

Creating Kafka Users

User Configuration

Access Control Lists (ACLs)

Connection Details

Required Permissions

Code Examples

Prerequisites

Troubleshooting

Getting Started

App

Deployment

Sources

Destinations

Transformation

Billing

Security

Rest API

​Creating Kafka Users

​User Configuration

​Access Control Lists (ACLs)

​Connection Details

​Required Permissions

​Code Examples

​Prerequisites

​Troubleshooting

Creating Kafka Users

User Configuration

Access Control Lists (ACLs)

Connection Details

Required Permissions

Code Examples

Prerequisites

Troubleshooting