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Chapter 3. Kafka Bridge configuration

Configure a deployment of the Kafka Bridge using configuration properties. Configure Kafka and specify the HTTP connection details needed to be able to interact with Kafka. You can also use configuration properties to enable and use distributed tracing with the Kafka Bridge. Distributed tracing allows you to track the progress of transactions between applications in a distributed system.

Note

Use the KafkaBridge resource to configure properties when you are running the Kafka Bridge on OpenShift.

3.1. Configuring Kafka Bridge properties
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This procedure describes how to configure the Kafka and HTTP connection properties used by the Kafka Bridge.

You configure the Kafka Bridge, as any other Kafka client, using appropriate prefixes for Kafka-related properties.

  • kafka. for general configuration that applies to producers and consumers, such as server connection and security.
  • kafka.consumer. for consumer-specific configuration passed only to the consumer.
  • kafka.producer. for producer-specific configuration passed only to the producer.

As well as enabling HTTP access to a Kafka cluster, HTTP properties provide the capability to enable and define access control for the Kafka Bridge through Cross-Origin Resource Sharing (CORS). CORS is a HTTP mechanism that allows browser access to selected resources from more than one origin. To configure CORS, you define a list of allowed resource origins and HTTP methods to access them. Additional HTTP headers in requests describe the CORS origins that are permitted access to the Kafka cluster.

Prerequisites

Procedure

  1. Edit the application.properties file provided with the Kafka Bridge installation archive.

    Use the properties file to specify Kafka and HTTP-related properties.

    1. Configure standard Kafka-related properties, including properties specific to the Kafka consumers and producers.

      Use:

      • kafka.bootstrap.servers to define the host/port connections to the Kafka cluster
      • kafka.producer.acks to provide acknowledgments to the HTTP client

      • kafka.consumer.auto.offset.reset to determine how to manage reset of the offset in Kafka

        For more information on configuration of Kafka properties, see the Apache Kafka website

    2. Configure HTTP-related properties to enable HTTP access to the Kafka cluster.

      For example: 

      bridge.id=my-bridge
http.host=0.0.0.0
http.port=8080
      1 
      
http.cors.enabled=true
      2 
      
http.cors.allowedOrigins=https://strimzi.io
      3 
      
http.cors.allowedMethods=GET,POST,PUT,DELETE,OPTIONS,PATCH
      4
      Copy to Clipboard Toggle word wrap
      1
      The default HTTP configuration for the Kafka Bridge to listen on port 8080.
      2
      Set to true to enable CORS.
      3
      Comma-separated list of allowed CORS origins. You can use a URL or a Java regular expression.
      4
      Comma-separated list of allowed HTTP methods for CORS.
  2. Save the configuration file.

3.2. Configuring distributed tracing
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Enable distributed tracing to trace messages consumed and produced by the Kafka Bridge, and HTTP requests from client applications.

Properties to enable tracing are present in the application.properties file. To enable distributed tracing, do the following:

  • Set the bridge.tracing property value to enable the tracing you want to use. Possible values are jaeger and opentelemetry.
  • Set environment variables for tracing.

With the default configuration, OpenTelemetry tracing uses OTLP as the exporter protocol. By configuring the OTLP endpoint, you can still use a Jaeger backend instance to get traces.

Note

Jaeger has supported the OTLP protocol since version 1.35. Older Jaeger versions cannot get traces using the OTLP protocol.

OpenTelemetry and OpenTracing are API specifications for collecting tracing data as spans of metrics data. Spans represent a specific operation. A trace is a collection of one or more spans.

Traces are generated when the Kafka Bridge does the following:

  • Sends messages from Kafka to consumer HTTP clients
  • Receives messages from producer HTTP clients to send to Kafka

Jaeger implements the required APIs and presents visualizations of the trace data in its user interface for analysis.

To have end-to-end tracing, you must configure tracing in your HTTP clients.

Important

The OpenTracing project is now archived, so AMQ Streams has deprecated support for OpenTracing. If possible, we will maintain the support for bridge.tracing=jaeger tracing until June 2023 and remove it afterwards. Please migrate to OpenTelemetry as soon as possible.

Prerequisites

Procedure

  1. Edit the application.properties file provided with the Kafka Bridge installation archive.

    Use the bridge.tracing property to enable the tracing you want to use.

    Example configuration to enable OpenTelemetry

    #bridge.tracing=jaeger
    1 
    
bridge.tracing=opentelemetry
    2
    Copy to Clipboard Toggle word wrap

    1
    The property for enabling OpenTracing (deprecated). Here left commented.
    2
    The property for enabling OpenTelemetry is uncommented.

    With tracing enabled, you initialize tracing when you run the Kafka Bridge script.

  2. Save the configuration file.

  3. Set the environment variables for tracing.

    Environment variables for OpenTelemetry

    OTEL_SERVICE_NAME=my-tracing-service
    1 
    
OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4317
    2
    Copy to Clipboard Toggle word wrap

    1
    The name of the OpenTelemetry tracer service.
    2
    The gRPC-based OTLP endpoint that listens for spans on port 4317.

    Environment variables for OpenTracing

    JAEGER_SERVICE_NAME=my-jaeger-service
    1 
    
JAEGER_AGENT_HOST=localhost
    2 
    
JAEGER_AGENT_PORT=6831
    3
    Copy to Clipboard Toggle word wrap

    1
    The name of the OpenTracing Jaeger tracer service.
    2
    The hostname for communicating with the Jaeger agent that listens for spans.
    3
    The port for communicating with the Jaeger agent. Port 6831 is exposed by the Jaeger agent.

  4. Run the Kafka Bridge script with the property enabled for tracing:

    Running the Kafka Bridge with OpenTelemetry enabled

    ./bin/kafka_bridge_run.sh --config-file=<path>/application.properties
    Copy to Clipboard Toggle word wrap

    The internal consumers and producers of the Kafka Bridge are now enabled for tracing.

Instead of the default OTLP tracing system, you can specify other tracing systems that are supported by OpenTelemetry.

If you want to use another tracing system with OpenTelemetry, do the following:

  1. Add the library of the tracing system to the Kafka classpath.

  2. Add the name of the tracing system as an additional exporter environment variable.

    Additional environment variable when not using OTLP

    OTEL_SERVICE_NAME=my-tracing-service
OTEL_TRACES_EXPORTER=zipkin
    1 
    
OTEL_EXPORTER_ZIPKIN_ENDPOINT=http://localhost:9411/api/v2/spans
    2
    Copy to Clipboard Toggle word wrap

    1
    The name of the tracing system. In this example, Zipkin is specified.
    2
    The endpoint of the specific selected exporter that listens for spans. In this example, a Zipkin endpoint is specified.
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