Apache Kafka

Detailed documentation on the Apache Kafka pubsub component

Component format

To set up Apache Kafka pub/sub, create a component of type pubsub.kafka. See the pub/sub broker component file to learn how ConsumerID is automatically generated. Read the How-to: Publish and Subscribe guide on how to create and apply a pub/sub configuration.

All component metadata field values can carry templated metadata values, which are resolved on Dapr sidecar startup. For example, you can choose to use {namespace} as the consumerGroup to enable using the same appId in different namespaces using the same topics as described in this article.

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: kafka-pubsub
spec:
  type: pubsub.kafka
  version: v1
  metadata:
  - name: brokers # Required. Kafka broker connection setting
    value: "dapr-kafka.myapp.svc.cluster.local:9092"
  - name: consumerGroup # Optional. Used for input bindings.
    value: "{namespace}"
  - name: consumerID # Optional. If not supplied, runtime will create one.
    value: "channel1"
  - name: clientID # Optional. Used as client tracing ID by Kafka brokers.
    value: "my-dapr-app-id"
  - name: authType # Required.
    value: "password"
  - name: saslUsername # Required if authType is `password`.
    value: "adminuser"
  - name: saslPassword # Required if authType is `password`.
    secretKeyRef:
      name: kafka-secrets
      key: saslPasswordSecret
  - name: saslMechanism
    value: "SHA-512"
  - name: maxMessageBytes # Optional.
    value: 1024
  - name: consumeRetryInterval # Optional.
    value: 200ms
  - name: version # Optional.
    value: 0.10.2.0
  - name: disableTls # Optional. Disable TLS. This is not safe for production!! You should read the `Mutual TLS` section for how to use TLS.
    value: "true"

For details on using secretKeyRef, see the guide on how to reference secrets in components.

Spec metadata fields

The secretKeyRef above is referencing a kubernetes secrets store to access the tls information. Visit here to learn more about how to configure a secret store component.

Note

The metadata version must be set to 1.0.0 when using Azure EventHubs with Kafka.

Authentication

Kafka supports a variety of authentication schemes and Dapr supports several: SASL password, mTLS, OIDC/OAuth2. With the added authentication methods, the authRequired field has been deprecated from the v1.6 release and instead the authType field should be used. If authRequired is set to true, Dapr will attempt to configure authType correctly based on the value of saslPassword. There are four valid values for authType: none, password, certificate, mtls, and oidc. Note this is authentication only; authorization is still configured within Kafka.

None

Setting authType to none will disable any authentication. This is NOT recommended in production.

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: kafka-pubsub-noauth
spec:
  type: pubsub.kafka
  version: v1
  metadata:
  - name: brokers # Required. Kafka broker connection setting
    value: "dapr-kafka.myapp.svc.cluster.local:9092"
  - name: consumerGroup # Optional. Used for input bindings.
    value: "group1"
  - name: clientID # Optional. Used as client tracing ID by Kafka brokers.
    value: "my-dapr-app-id"
  - name: authType # Required.
    value: "none"
  - name: maxMessageBytes # Optional.
    value: 1024
  - name: consumeRetryInterval # Optional.
    value: 200ms
  - name: version # Optional.
    value: 0.10.2.0
  - name: disableTls
    value: "true"

SASL Password

Setting authType to password enables SASL authentication. This requires setting the saslUsername and saslPassword fields.

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: kafka-pubsub-sasl
spec:
  type: pubsub.kafka
  version: v1
  metadata:
  - name: brokers # Required. Kafka broker connection setting
    value: "dapr-kafka.myapp.svc.cluster.local:9092"
  - name: consumerGroup # Optional. Used for input bindings.
    value: "group1"
  - name: clientID # Optional. Used as client tracing ID by Kafka brokers.
    value: "my-dapr-app-id"
  - name: authType # Required.
    value: "password"
  - name: saslUsername # Required if authType is `password`.
    value: "adminuser"
  - name: saslPassword # Required if authType is `password`.
    secretKeyRef:
      name: kafka-secrets
      key: saslPasswordSecret
  - name: saslMechanism
    value: "SHA-512"
  - name: maxMessageBytes # Optional.
    value: 1024
  - name: consumeRetryInterval # Optional.
    value: 200ms
  - name: version # Optional.
    value: 0.10.2.0
  - name: caCert
    secretKeyRef:
      name: kafka-tls
      key: caCert

Mutual TLS

Setting authType to mtls uses a x509 client certificate (the clientCert field) and key (the clientKey field) to authenticate. Note that mTLS as an authentication mechanism is distinct from using TLS to secure the transport layer via encryption. mTLS requires TLS transport (meaning disableTls must be false), but securing the transport layer does not require using mTLS. See Communication using TLS for configuring underlying TLS transport.

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: kafka-pubsub-mtls
spec:
  type: pubsub.kafka
  version: v1
  metadata:
  - name: brokers # Required. Kafka broker connection setting
    value: "dapr-kafka.myapp.svc.cluster.local:9092"
  - name: consumerGroup # Optional. Used for input bindings.
    value: "group1"
  - name: clientID # Optional. Used as client tracing ID by Kafka brokers.
    value: "my-dapr-app-id"
  - name: authType # Required.
    value: "mtls"
  - name: caCert
    secretKeyRef:
      name: kafka-tls
      key: caCert
  - name: clientCert
    secretKeyRef:
      name: kafka-tls
      key: clientCert
  - name: clientKey
    secretKeyRef:
      name: kafka-tls
      key: clientKey
  - name: maxMessageBytes # Optional.
    value: 1024
  - name: consumeRetryInterval # Optional.
    value: 200ms
  - name: version # Optional.
    value: 0.10.2.0

OAuth2 or OpenID Connect

Setting authType to oidc enables SASL authentication via the OAUTHBEARER mechanism. This supports specifying a bearer token from an external OAuth2 or OIDC identity provider. Currently, only the client_credentials grant is supported.

Configure oidcTokenEndpoint to the full URL for the identity provider access token endpoint.

Set oidcClientID and oidcClientSecret to the client credentials provisioned in the identity provider.

If caCert is specified in the component configuration, the certificate is appended to the system CA trust for verifying the identity provider certificate. Similarly, if skipVerify is specified in the component configuration, verification will also be skipped when accessing the identity provider.

By default, the only scope requested for the token is openid; it is highly recommended that additional scopes be specified via oidcScopes in a comma-separated list and validated by the Kafka broker. If additional scopes are not used to narrow the validity of the access token, a compromised Kafka broker could replay the token to access other services as the Dapr clientID.

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: kafka-pubsub
spec:
  type: pubsub.kafka
  version: v1
  metadata:
  - name: brokers # Required. Kafka broker connection setting
    value: "dapr-kafka.myapp.svc.cluster.local:9092"
  - name: consumerGroup # Optional. Used for input bindings.
    value: "group1"
  - name: clientID # Optional. Used as client tracing ID by Kafka brokers.
    value: "my-dapr-app-id"
  - name: authType # Required.
    value: "oidc"
  - name: oidcTokenEndpoint # Required if authType is `oidc`.
    value: "https://identity.example.com/v1/token"
  - name: oidcClientID      # Required if authType is `oidc`.
    value: "dapr-myapp"
  - name: oidcClientSecret  # Required if authType is `oidc`.
    secretKeyRef:
      name: kafka-secrets
      key: oidcClientSecret
  - name: oidcScopes        # Recommended if authType is `oidc`.
    value: "openid,kafka-dev"
  - name: caCert            # Also applied to verifying OIDC provider certificate
    secretKeyRef:
      name: kafka-tls
      key: caCert
  - name: maxMessageBytes # Optional.
    value: 1024
  - name: consumeRetryInterval # Optional.
    value: 200ms
  - name: version # Optional.
    value: 0.10.2.0

Communication using TLS

By default TLS is enabled to secure the transport layer to Kafka. To disable TLS, set disableTls to true. When TLS is enabled, you can control server certificate verification using skipVerify to disable verification (NOT recommended in production environments) and caCert to specify a trusted TLS certificate authority (CA). If no caCert is specified, the system CA trust will be used. To also configure mTLS authentication, see the section under Authentication. Below is an example of a Kafka pubsub component configured to use transport layer TLS:

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: kafka-pubsub
spec:
  type: pubsub.kafka
  version: v1
  metadata:
  - name: brokers # Required. Kafka broker connection setting
    value: "dapr-kafka.myapp.svc.cluster.local:9092"
  - name: consumerGroup # Optional. Used for input bindings.
    value: "group1"
  - name: clientID # Optional. Used as client tracing ID by Kafka brokers.
    value: "my-dapr-app-id"
  - name: authType # Required.
    value: "certificate"
  - name: consumeRetryInterval # Optional.
    value: 200ms
  - name: version # Optional.
    value: 0.10.2.0
  - name: maxMessageBytes # Optional.
    value: 1024
  - name: caCert # Certificate authority certificate.
    secretKeyRef:
      name: kafka-tls
      key: caCert
auth:
  secretStore: <SECRET_STORE_NAME>

Sending and receiving multiple messages

Apache Kafka component supports sending and receiving multiple messages in a single operation using the bulk Pub/sub API.

Configuring bulk subscribe

When subscribing to a topic, you can configure bulkSubscribe options. Refer to Subscribing messages in bulk for more details. Learn more about the bulk subscribe API.

Apache Kafka supports the following bulk metadata options:

Per-call metadata fields

Partition Key

When invoking the Kafka pub/sub, its possible to provide an optional partition key by using the metadata query param in the request url.

The param name is partitionKey.

Example:

curl -X POST http://localhost:3500/v1.0/publish/myKafka/myTopic?metadata.partitionKey=key1 \
  -H "Content-Type: application/json" \
  -d '{
        "data": {
          "message": "Hi"
        }
      }'

Message headers

All other metadata key/value pairs (that are not partitionKey) are set as headers in the Kafka message. Here is an example setting a correlationId for the message.

curl -X POST http://localhost:3500/v1.0/publish/myKafka/myTopic?metadata.correlationId=myCorrelationID&metadata.partitionKey=key1 \
  -H "Content-Type: application/json" \
  -d '{
        "data": {
          "message": "Hi"
        }
      }'

Create a Kafka instance

• Self-Hosted
• Kubernetes

You can run Kafka locally using this Docker image. To run without Docker, see the getting started guide here.

To run Kafka on Kubernetes, you can use any Kafka operator, such as Strimzi.

Related links

• Basic schema for a Dapr component
• Read this guide for instructions on configuring pub/sub components
• Pub/Sub building block

Last modified October 12, 2023: Update config.toml (#3826) (0ffc2e7)