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Code Block
languagetext
titleKafkaConnect
apiVersion: kafka.strimzi.io/v1beta1
kind: KafkaUser
metadata:
  name: connect
  namespace: kafka
  labels:
    strimzi.io/cluster: my-cluster
spec:
  authentication:
    type: tls
---
apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaConnect
metadata:
  name: my-connect-cluster
  namespace: kafka
  annotations:
  # use-connector-resources configures this KafkaConnect
  # to use KafkaConnector resources to avoid
  # needing to call the Connect REST API directly
    strimzi.io/use-connector-resources: "true"
spec:   
  image: ktimoney/strimzi-influxdb-connect
  replicas: 1
  bootstrapServers: my-cluster-kafka-bootstrap:9093
  tls:
    trustedCertificates:
      - secretName: my-cluster-cluster-ca-cert
        certificate: ca.crt
      - secretName: my-cluster-clients-ca-cert
        certificate: ca.crt
  authentication:
    type: tls
    certificateAndKey:
      secretName: connect
      certificate: user.crt
      key: user.key
  config:
    group.id: connect-cluster
    offset.storage.topic: connect-cluster-offsets
    config.storage.topic: connect-cluster-configs
    status.storage.topic: connect-cluster-status
    offset.storage.topic: my-connect-cluster-offsets
    config.storage.topic: my-connect-cluster-configs
    status.storage.topic: my-connect-cluster-status
    config.storage.replication.factor: 1
    offset.storage.replication.factor: 1
    status.storage.replication.factor: 1

...

The KafkaConnector is configured to use the "org.apache.camel.kafkaconnector.influxdb.CamelInfluxdbSinkConnector" class.

The value converter are is set to "org.apache.kafka.connect.json.JsonConverter".

...

Code Block
languagetext
titleInfluxDB query
{'pretty': 'true', 'db': 'ts_host_metrics', 'q': 'SELECT "region", "host", "free", "used" FROM "disk_space" WHERE "host"=\'localhost\''}
{
    "results": [
        {
            "statement_id": 0,
            "series": [
                {
                    "name": "disk_space",
                    "columns": [
                        "time",
                        "region",
                        "host",
                        "free",
                        "used"
                    ],
                    "values": [
                        [
                            "2023-01-23T13:03:32.1246436Z",
                            "IE-region",
                            "localhost",
                            "81%",
                            "19%"
                        ]
                    ]
                }
            ]
        }
    ]
}

Links

Kafka Connect And Schemas


Minio Sink Connector (Apache Camel)

Prepare the connector image

Download the minio sink connector: wget https://repo.maven.apache.org/maven2/org/apache/camel/kafkaconnector/camel-file-kafka-connector/3.20.0/camel-file-kafka-connector-3.20.0-package.tar.gz


We need to create some custom classes:

CamelMinioConverters.java - this will allow us to deserialize to json and convert the hashmap to an inputstream

Code Block
languagejava
titleCamelMinioConverters
package com.custom.convert.minio;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.util.Map;
import org.apache.camel.Converter;

@Converter(generateLoader = true)
public final class CamelMinioConverters {

    private CamelMinioConverters() {
    }

    @SuppressWarnings("deprecation")
    @Converter
    public static InputStream fromMapToInputStream(Map<String, Object> map) {

      String json = "{}";
      try {
        json = new ObjectMapper().writeValueAsString(map);
      } catch (JsonProcessingException e) {
        e.printStackTrace();
      }
     return new ByteArrayInputStream(json.getBytes());
    }

}


StringAggregator.java - this will allow us to aggregate the messages and set the file name

Code Block
languagejava
titleStringAggregator
package com.custom.aggregate.minio;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import org.apache.camel.AggregationStrategy;
import org.apache.camel.Exchange;
import org.apache.camel.Message;

public class CustomStringAggregator implements AggregationStrategy {

    //@Override
    public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
      Message newIn = newExchange.getIn();
      Map<String, String> keyMap = (HashMap) newIn.getHeaders().get("camel.kafka.connector.record.key");
      String key = keyMap.get("id");
      SimpleDateFormat sdf = new SimpleDateFormat("ddMMyy-hhmmss-SSS");              
      String fileName = "ExchangeKafka-" + key + "-" + sdf.format( new Date() ) + ".json";
      newIn.setHeader("file", fileName);               

     // lets append the old body to the new body
        if (oldExchange == null) {
            return newExchange;
        }

        String body = oldExchange.getIn().getBody(String.class);
        if (body != null) {
            String newBody = newIn.getBody(String.class);
            if (newBody != null) {
                body += System.lineSeparator() + newBody;
            }

            newIn.setBody(body);
        }
        return newExchange;
    }
}

We can then create a custom jar for our code and copy it into the docker container.

Note: You can also set the filename in the Kafka header using either CamelHeader.file or CamelHeader.ce-file


Create a docker file for this connector


Code Block
languagetext
titleDocker
FROM quay.io/strimzi/kafka:0.32.0-kafka-3.3.1
USER root:root
RUN mkdir -p /opt/kafka/plugins/camel
COPY ./camel-minio-sink-kafka-connector-3.20.0-package.tar.gz /opt/kafka/plugins/camel/
RUN tar -xvzf /opt/kafka/plugins/camel/camel-minio-sink-kafka-connector-3.20.0-package.tar.gz --directory /opt/kafka/plugins/camel
COPY ./custom-converter-1.0.0.jar /opt/kafka/plugins/camel/camel-minio-sink-kafka-connector/
RUN rm /opt/kafka/plugins/camel/camel-minio-sink-kafka-connector-3.20.0-package.tar.gzRUN rm -rf /opt/kafka/plugins/camel/docs
USER 1001

Build the image and copy it to your docker repository

docker build -f Dockerfile . t ktimoney/strimzi_minio_connector



Prepare the message producer

In this example we are going to deserialize the value to a string. (Same producer as the influxdb example)

They will take the following format:

Code Block
languagejs
titleSchema & Payload
{
"camelInfluxDB.MeasurementName":"disk_space"
"time":"2023-01-23T13:03:31Z"
"host":"localhost"
"region":"IE-region"
"used":"19%"
"free":"81%"
}

With the type converter n place we can also deserialize as a json object.

They key will be a json that loos like this: {"id":"119"} 


Create the KafkaConnect object

Code Block
languagetext
titleKafkaConnect
apiVersion: kafka.strimzi.io/v1beta1
kind: KafkaUser
metadata:
  name: connect
  namespace: kafka
  labels:
    strimzi.io/cluster: my-cluster
spec:
  authentication:
    type: tls
---
apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaConnect
metadata:
  name: my-connect-cluster
  namespace: kafka
  annotations:
  # use-connector-resources configures this KafkaConnect
  # to use KafkaConnector resources to avoid
  # needing to call the Connect REST API directly
    strimzi.io/use-connector-resources: "true"
spec:   
  image: ktimoney/strimzi-minio-connect
  replicas: 1
  bootstrapServers: my-cluster-kafka-bootstrap:9093
  tls:
    trustedCertificates:
      - secretName: my-cluster-cluster-ca-cert
        certificate: ca.crt
      - secretName: my-cluster-clients-ca-cert
        certificate: ca.crt
  authentication:
    type: tls
    certificateAndKey:
      secretName: connect
      certificate: user.crt
      key: user.key
  config:
    group.id: connect-cluster      
    offset.storage.topic: connect-cluster-offsets
    config.storage.topic: connect-cluster-configs
    status.storage.topic: connect-cluster-status
    # -1 means it will use the default replication factor configured in the broker
    config.storage.replication.factor: -1
    offset.storage.replication.factor: -1
    status.storage.replication.factor: -1


We are connecting to the 9093 tls port so we include required certificates in our configuration.

The image tag references the image we built earlier : ktimoney/strimzi-minio-connect


Create the Sink connector

Code Block
languagetext
titleKafkaConnector
apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaConnector
metadata:
  name: my-sink-connector
  namespace: kafka
  labels:
    strimzi.io/cluster: my-connect-cluster
spec:   
  class: org.apache.camel.kafkaconnector.miniosink.CamelMiniosinkSinkConnector   
  tasksMax: 1   
  config:
    topics: my-topic
    key.converter: org.apache.kafka.connect.json.JsonConverter
    value.converter: org.apache.kafka.connect.storage.StringConverter
    key.converter.schemas.enable: false
    value.converter.schemas.enable: false         
    camel.beans.aggregate: "#class:com.custom.aggregate.minio.CustomStringAggregator"
    camel.aggregation.size: 1
    camel.aggregation.timeout: 20000
    camel.aggregation.disable: false     
    camel.kamelet.minio-sink.bucketName: camel
    camel.kamelet.minio-sink.accessKey: ybK7RleFUkdDeYBf
    camel.kamelet.minio-sink.secretKey: X0Y4zK84bwdefRTljrnPzOb1l0A6OQj2
    camel.kamelet.minio-sink.endpoint: http://minio.default:9000
    camel.kamelet.minio-sink.autoCreateBucket: true


The KafkaConnector is configured to use the "org.apache.camel.kafkaconnector.miniosink.CamelMiniosinkSinkConnector class.

The value converter is set to "org.apache.kafka.connect.storage.StringConverter".

The minio connection details are specified in camel.kamelet.minio-sink parameters.

The aggregation size is set to 1 so it won't aggregate any of the files

This timeout is also specified so it will only aggregate records arriving within this time out value (20 seconds).

These values can be adjusted depending on your requirements.

The main purpose of the aggregator in this example is for setting the file name, this is done by setting a header with a key of "file".

The yaml for the minio pod is available here: minio.yaml


When the connector is running it copies the kafka records into minio as files:

Image Added


Here's a screen shot where we use the aggregator to set the file name:

Image Added



File Sink Connector (Apache Camel)

Prepare the connector image

Download the file connector: wget https://repo.maven.apache.org/maven2/org/apache/camel/kafkaconnector/camel-file-kafka-connector/3.20.0/camel-file-kafka-connector-3.20.0-package.tar.gz

Create a docker file for this connector


Code Block
languagetext
titleDocker
FROM quay.io/strimzi/kafka:0.32.0-kafka-3.3.1
USER root:root
RUN mkdir -p /opt/kafka/plugins/camel
COPY ./camel-file-kafka-connector-3.20.0-package.tar.gz /opt/kafka/plugins/camel/
RUN tar -xvzf /opt/kafka/plugins/camel/camel-file-kafka-connector-3.20.0-package.tar.gz --directory /opt/kafka/plugins/camel
RUN rm /opt/kafka/plugins/camel/camel-file-kafka-connector-3.20.0-package.tar.gz
RUN rm -rf /opt/kafka/plugins/camel/docs
USER 1001

Build the image and copy it to your docker repository

docker build -f Dockerfile . t ktimoney/strimzi_file_connector



Prepare the message producer

In this example we are going to deserialize the value to a string.

The value will take the following format:

Code Block
languagejs
titleSchema & Payload
{
"camelInfluxDB.MeasurementName":"disk_space"
"time":"2023-01-23T13:03:31Z"
"host":"localhost"
"region":"IE-region"
"used":"19%"
"free":"81%"
}



Due to some limitation with Strimzi KafkaConnect we will need to use a mutating webhook to attach a persistent volume to our connector pod.

The go code for this is available here:  kafka-webhook.go

We need to create a docker image for this program

Code Block
languagetext
titleWebhook docker
FROM golang:latest
RUN mkdir /app
COPY ./kafka-webhook /app
RUN chmod +x /app/kafka-webhook
WORKDIR /app
ENTRYPOINT ["/app/kafka-webhook"]

docker build -f Dockerfile . -t ktimoney/kafka-webhook

Mutating webhooks require https so we also need to create some certificates.

Make sure cfssl is installed on you system, then run the following commands.

cfssl gencert -initca ./ca-csr.json | cfssljson -bare ca

cfssl gencert \
  -ca=ca.pem \
  -ca-key=ca-key.pem \
  -config=ca-config.json \
  -hostname="kafka-webhook,kafka-webhook.kafka.svc.cluster.local,kafka-webhook.kafka.svc,localhost,127.0.0.1" \
  -profile=default \
  ca-csr.json | cfssljson -bare webhook-cert


Run the following commands to create the values you need to use in the yaml file:

TLS_CRT=$(cat webhook-cert.pem | base64 | tr -d '\n')

TLS_KEY=$(cat webhook-cert-key.pem | base64 | tr -d '\n')

CA_BUNDLE="$(openssl base64 -A <"ca.pem")"

Replace the values in : kafka-webhook.yaml

Note: You can also configure the hostPath and the containerPath as part of the deployment:

Code Block
languageyml
titleContainer command args
      containers:
      - name: kafka-webhook
        image: ktimoney/kafka-webhook
        imagePullPolicy: IfNotPresent
        command: ["/app/kafka-webhook"]
        args: [
                "-port", "8443",
                "-tlsCertFile", "/certs/tls.crt",
                "-tlsKeyFile", "/certs/tls.key",
                "-hostPath", "/var/strimzi/files",
                "-containerPath", "/opt/kafka/data"
              ]



Run: kubectl create -f kafka webhook.yaml to start the pod.

Note: You can delete the webhook once the connector pod starts.


Create the KafkaConnect object

Code Block
languagetext
titleKafkaConnect
apiVersion: kafka.strimzi.io/v1beta1
kind: KafkaUser
metadata:
  name: connect
  namespace: kafka
  labels:
    strimzi.io/cluster: my-cluster
spec:
  authentication:
    type: tls
---
apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaConnect
metadata:
  name: my-connect-cluster
  namespace: kafka  
  labels:
    webhook: "true"
  annotations:
  # use-connector-resources configures this KafkaConnect
  # to use KafkaConnector resources to avoid
  # needing to call the Connect REST API directly
    strimzi.io/use-connector-resources: "true"
spec:   
  image: ktimoney/strimzi-file-connect
  replicas: 1
  bootstrapServers: my-cluster-kafka-bootstrap:9093
  tls:
    trustedCertificates:
      - secretName: my-cluster-cluster-ca-cert
        certificate: ca.crt
      - secretName: my-cluster-clients-ca-cert
        certificate: ca.crt
  authentication:
    type: tls
    certificateAndKey:
      secretName: connect
      certificate: user.crt
      key: user.key
  config:
    group.id: connect-cluster
    offset.storage.topic: connect-cluster-offsets
    config.storage.topic: connect-cluster-configs
    status.storage.topic: connect-cluster-status
    config.storage.replication.factor: 1
    offset.storage.replication.factor: 1
    status.storage.replication.factor: 1


We are connecting to the 9093 tls port so we include required certificates in our configuration.

The image tag references the image we built earlier : ktimoney/strimzi-file-connect

In the metadata section of KafkaConnect I have added a new label webhook: "true", this will be picked up by the MutatingWebhookConfiguration:


Code Block
languageyml
titleMutatingWebhookConfiguration
apiVersion: admissionregistration.k8s.io/v1
kind: MutatingWebhookConfiguration
metadata:
  name: kafka-webhook-config
  namespace: kafka
  annotations:
    cert-manager.io/inject-ca-from-secret: kafka/kafka-webhook-cert
webhooks:
  - name: kafka-webhook.kafka.svc.cluster.local
    admissionReviewVersions:
      - "v1"
    sideEffects: "None"
    timeoutSeconds: 30
    objectSelector:
      matchLabels:
        webhook: "true"

matchLabels: webhook: "true"


Create the Sink connector

Code Block
languagetext
titleKafkaConnector
apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaConnector
metadata:
  name: my-sink-connector
  namespace: kafka
  labels:
    strimzi.io/cluster: my-connect-cluster
spec:   
  class: org.apache.camel.kafkaconnector.file.CamelFileSinkConnector
  tasksMax: 1
  config:
    topics: my-topic 
    value.converter: org.apache.kafka.connect.storage.StringConverter
    key.converter: org.apache.kafka.connect.json.JsonConverter
    key.converter.schemas.enable: false
    value.converter.schemas.enable: false
    camel.sink.endpoint.fileName: mydata-${date:now:ddMMyy-hhmmss-SSS}.txt
    camel.sink.path.directoryName: /opt/kafka/data
    camel.sink.endpoint.fileExist: Append
    camel.sink.endpoint.autoCreate: true
    camel.aggregation.disable: true


The KafkaConnector is configured to use the "org.apache.camel.kafkaconnector.file.CamelFileSinkConnector" class.

The value converter is set to "org.apache.kafka.connect.storage.StringConverter".

The connector filename is set using the expression:  mydata-${date:now:ddMMyy-hhmmss-SSS}.txt

When the connector starts your kafka records will be copied to the persistent volume as files:

Image Added


Links

Kafka Connect And Schemas

Building your own Kafka Connect Building your own Kafka Connect image with a custom resource

...

How to Write a Connector for Kafka Connect – Deep Dive into Configuration Handling

Apache Camel

Camel Kafka Connector Examples

Camel Kafka Connect Maven Repository

Camel Basic Configuration

Camel Components Source Code

Camel Kafka Connector Source Code

Using secrets in Kafka Connect configuration

Kafka Connect Transformations