Delivering data from an Apache Kafka® queue to ClickHouse®

A Managed Service for ClickHouse® cluster can get data from Apache Kafka® topics in real time. This data will be automatically inserted into ClickHouse® Kafka tables.

To set up data delivery from Managed Service for Apache Kafka® to Managed Service for ClickHouse®:

1. Send test data to Managed Service for Apache Kafka® topic.
2. Set up and activate the transfer.
3. Test your transfer.

If you no longer need the resources you created, delete them.

Getting startedGetting started

Required paid resourcesRequired paid resources

The support cost includes:

• Managed Service for Apache Kafka® cluster fee: Using computing resources allocated to hosts (including ZooKeeper hosts) and disk space (see Apache Kafka® pricing).
• Managed Service for ClickHouse® cluster fee: Using computing resources allocated to hosts (including ZooKeeper hosts) and disk space (see Managed Service for ClickHouse® pricing).
• Fee for using public IP addresses if public access is enabled for cluster hosts (see Virtual Private Cloud pricing).

Set up the infrastructureSet up the infrastructure

Configure additional settingsConfigure additional settings

1. Install these tools:

   • kafkacat: To read and write data to the Apache Kafka® topic.

     sudo apt update && sudo apt install --yes kafkacat
     

     Check that you can use it to connect to Managed Service for Apache Kafka® clusters over SSL.

   • clickhouse-client: To connect to the database in the Managed Service for ClickHouse® cluster.

     1. Add the ClickHouse® DEB repository to your system:

        sudo apt update && sudo apt install --yes apt-transport-https ca-certificates dirmngr && \
        sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv E0C56BD4 && \
        echo "deb https://packages.clickhouse.com/deb stable main" | sudo tee \
        /etc/apt/sources.list.d/clickhouse.list
        

     2. Install the dependencies:

        sudo apt update && sudo apt install --yes clickhouse-client
        

     3. Download the clickhouse-client configuration file:

        mkdir -p ~/.clickhouse-client && \
        wget "https://storage.yandexcloud.net/doc-files/clickhouse-client.conf.example" \
          --output-document ~/.clickhouse-client/config.xml
        

     Check that you can use it to connect to the Managed Service for ClickHouse® cluster over SSL.

   • jq for stream processing of JSON files.

     sudo apt update && sudo apt-get install --yes jq
     

Send test data to the Managed Service for Apache Kafka® topicSend test data to the Managed Service for Apache Kafka® topic

Suppose that your Apache Kafka® topic receives data from car sensors. This data will be transmitted as Apache Kafka® messages in JSON format:

{
    "device_id":"iv9a94th6rzt********",
    "datetime":"2020-06-05 17:27:00",
    "latitude":"55.70329032",
    "longitude":"37.65472196",
    "altitude":"427.5",
    "speed":"0",
    "battery_voltage":"23.5",
    "cabin_temperature":"17",
    "fuel_level":null
}

The Managed Service for ClickHouse® cluster will use JSONEachRow data format to insert data into Kafka tables. This format converts strings from Apache Kafka® messages to relevant column values.

1. Create a sample.json file with test data:

   sample.json

   {
       "device_id": "iv9a94th6rzt********",
       "datetime": "2020-06-05 17:27:00",
       "latitude": 55.70329032,
       "longitude": 37.65472196,
       "altitude": 427.5,
       "speed": 0,
       "battery_voltage": 23.5,
       "cabin_temperature": 17,
       "fuel_level": null
   }
   
   {
       "device_id": "rhibbh3y08qm********",
       "datetime": "2020-06-06 09:49:54",
       "latitude": 55.71294467,
       "longitude": 37.66542005,
       "altitude": 429.13,
       "speed": 55.5,
       "battery_voltage": null,
       "cabin_temperature": 18,
       "fuel_level": 32
   }
   
   {
       "device_id": "iv9a94th6rzt********",
       "datetime": "2020-06-07 15:00:10",
       "latitude": 55.70985913,
       "longitude": 37.62141918,
       "altitude": 417.0,
       "speed": 15.7,
       "battery_voltage": 10.3,
       "cabin_temperature": 17,
       "fuel_level": null
   }
   

2. Send data from the sample.json file to the Managed Service for Apache Kafka® topic using jq and kafkacat:

   jq -rc . sample.json | kafkacat -P \
      -b <broker_host_FQDN>:9091 \
      -t <topic_name> \
      -k key \
      -X security.protocol=SASL_SSL \
      -X sasl.mechanisms=SCRAM-SHA-512 \
      -X sasl.username="<username_for_producer>" \
      -X sasl.password="<user_password_for_producer>" \
      -X ssl.ca.location=/usr/local/share/ca-certificates/Yandex/RootCA.crt -Z
   

Set up and activate the transferSet up and activate the transfer

1. Create a source endpoint:

   • Database type: Kafka

   • Endpoint parameters → Connection settings:

     • Connection type: Managed Service for Apache Kafka cluster

       • Managed Service for Apache Kafka cluster: Select the source cluster from the list.

       • Authentication:

         • Username: Enter the consumer username.
         • Password: Enter the consumer password.

     • Topic full name: Enter the name of the topic in the Managed Service for Apache Kafka® cluster.

     • Advanced settings → Conversion rules:

       • Data format: JSON

       • Data scheme: JSON specification:

         Copy and paste the data schema in JSON format:

         Data schema

         [
             {
                 "name": "device_id",
                 "type": "string"
             },
             {
                 "name": "datetime",
                 "type": "datetime"
             },
             {
                 "name": "latitude",
                 "type": "double"
             },
             {
                 "name": "longitude",
                 "type": "double"
             },
             {
                 "name": "altitude",
                 "type": "double"
             },
             {
                 "name": "speed",
                 "type": "double"
             },
             {
                 "name": "battery_voltage",
                 "type": "any"
             },
             {
                 "name": "cabin_temperature",
                 "type": "double"
             },
             {
                 "name": "fuel_level",
                 "type": "any"
             }
         ]
         

2. Create an endpoint for the target and transfer:

   Manually

   Terraform

   1. Create a target endpoint:

      • Database type: ClickHouse.

      • Endpoint parameters:

        • Connection settings:

          • Connection type: Managed cluster.

            • Managed cluster: Select the source cluster from the list.

          • Database: Enter the database name.

          • User and Password: Enter the name and password of the user having access to the database, e.g., the database owner.

        • Advanced settings → Upload data in JSON format: Enable this option if you enabled Conversion rules in the advanced settings of the source endpoint.

   2. Create a transfer of the Replication type that will use the created endpoints.

   3. Activate your transfer.

   1. In the data-transfer-mkf-mch.tf file, uncomment the following:

      • The source_endpoint_id variable and set it to the value of the endpoint ID for the source created in the previous step.
      • yandex_datatransfer_endpoint and yandex_datatransfer_transfer resources.

   2. Validate your Terraform configuration files using this command:

      terraform validate
      

      Terraform will display any configuration errors detected in your files.

   3. Create the required infrastructure:

      1. Run this command to view the planned changes:

         terraform plan
         

         If you described the configuration correctly, the terminal will display a list of the resources to update and their parameters. This is a verification step that does not apply changes to your resources.

      2. If everything looks correct, apply the changes:

         1. Run this command:

            terraform apply
            

         2. Confirm updating the resources.

         3. Wait for the operation to complete.

      Once created, your transfer is activated automatically.

Test your transferTest your transfer

1. Wait for the transfer status to change to Replicating.

2. Make sure the data from the source Managed Service for Apache Kafka® cluster has been moved to the Managed Service for ClickHouse® database:

   1. Connect to the cluster using clickhouse-client.

   2. Run this query:

      SELECT * FROM <ClickHouse®_database_name>.<Apache_Kafka_topic_name>
      

3. Change values in the sample.json file and send data from it to the Managed Service for Apache Kafka® topic:

   jq -rc . sample.json | kafkacat -P \
      -b <broker_host_FQDN>:9091 \
      -t <topic_name> \
      -k key \
      -X security.protocol=SASL_SSL \
      -X sasl.mechanisms=SCRAM-SHA-512 \
      -X sasl.username="<username_for_producer>" \
      -X sasl.password="<user_password_for_producer>" \
      -X ssl.ca.location=/usr/local/share/ca-certificates/Yandex/RootCA.crt -Z
   

4. Make sure that the new values are now in the Managed Service for ClickHouse® database:

   1. Connect to the cluster using clickhouse-client.

   2. Run this query:

      SELECT * FROM <ClickHouse®_database_name>.<Apache_Kafka_topic_name>
      

Delete the resources you createdDelete the resources you created

Some resources are not free of charge. To avoid unnecessary charges, delete the resources you no longer need:

1. Delete the transfer.
2. Delete the source endpoint.

Delete other resources using the method matching their creation method:

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