Delivering data from an Apache Kafka® queue to PostgreSQL

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Updated at November 7, 2024

Getting started
Prepare the test data
Prepare and activate the transfer
Test the transfer
Delete the resources you created

You can set up data transfer from a Managed Service for Apache Kafka® topic to Managed Service for PostgreSQL using Yandex Data Transfer. To do this:

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

Getting started

Prepare the infrastructure:
Manually

Terraform
1. Create a Managed Service for Apache Kafka® source cluster in any availability zone with any suitable configuration and public access.
2. In the source cluster, create a topic named sensors.
3. In the source cluster, create a user named mkf-user with the ACCESS_ROLE_PRODUCER and ACCESS_ROLE_CONSUMER access permissions for the topic.
4. In the same availability zone, create a Managed Service for PostgreSQL target cluster in any appropriate configuration with pg-user as the admin user and publicly available hosts.
5. Make sure that the cluster security groups are set up correctly and allow connecting to them:
  - Managed Service for Apache Kafka®.
  - Managed Service for PostgreSQL.
1. If you do not have Terraform yet, install it.
2. Get the authentication credentials. You can add them to environment variables or specify them later in the provider configuration file.
3. Configure and initialize a provider. There is no need to create a provider configuration file manually, you can download it.
4. Place the configuration file in a separate working directory and specify the parameter values. If you did not add the authentication credentials to environment variables, specify them in the configuration file.
5. Download the kafka-postgresql.tf configuration file to the same working directory.
  
  This file describes:
  - Networks and subnets for hosting the clusters.
  - Security groups for making cluster connections.
  - Managed Service for Apache Kafka® source cluster.
  - Managed Service for PostgreSQL target cluster.
  - Target endpoint.
  - Transfer.
6. Specify the following in the kafka-postgresql.tf file:
  - Apache Kafka® and PostgreSQL versions
  - Apache Kafka® and PostgreSQL user passwords
7. Make sure the Terraform configuration files are correct using this command:
  terraform validate
  If there are any errors in the configuration files, Terraform will point them out.
8. Create the required infrastructure:
  1. Run the command to view planned changes:
    
    terraform plan
    
    If the resource configuration descriptions are correct, the terminal will display a list of the resources to modify and their parameters. This is a test step. No resources are updated.
  2. If you are happy with the planned changes, apply them:
    
    Run the command:
    
    terraform apply
    
    Confirm the update of resources.
    
    Wait for the operation to complete.
  All the required resources will be created in the specified folder. You can check resource availability and their settings in the management console.
Install the utilities:
- kafkacat to read and write data to Apache Kafka® topics.
```
sudo apt update && sudo apt install --yes kafkacat
```
  Check that you can use it to connect to the Managed Service for Apache Kafka® source cluster over SSL.
- jq for JSON file stream processing.
```
sudo apt update && sudo apt-get install --yes jq
```

Prepare the test data

Let's assume the Apache Kafka® sensors topic in the source cluster receives data from car sensors in JSON format.

Create a local sample.json file with the following 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
}

Prepare and activate the transfer

Create a source endpoint with the Apache Kafka® type and specify the following items for it:

Topic full name: sensors.
json conversion rules. In the Data scheme field, select JSON specification and copy and paste the following field specification into the form that opens:

sensors-specification

[
    {
        "name": "device_id",
        "type": "utf8",
        "key": true
    },
    {
        "name": "datetime",
        "type": "utf8"
    },
    {
        "name": "latitude",
        "type": "double"
    },
    {
        "name": "longitude",
        "type": "double"
    },
    {
        "name": "altitude",
        "type": "double"
    },
    {
        "name": "speed",
        "type": "double"
    },
    {
        "name": "battery_voltage",
        "type": "double"
    },
    {
        "name": "cabin_temperature",
        "type": "uint16"
    },
    {
        "name": "fuel_level",
        "type": "uint16"
    }
]

Create a target endpoint and a transfer:
Manually

Terraform
1. Create a target endpoint of the PostgreSQL type and specify the cluster connection parameters in it:
  - Installation type: Managed Service for PostgreSQL cluster.
  - Managed Service for PostgreSQL cluster: <target_PostgreSQL_cluster_name> from the drop-down list.
  - Database: db1.
  - User: pg-user.
  - Password: <user_password>.
2. Create a transfer of the Replication type that will use the created endpoints.
3. Activate the transfer and wait for its status to change to Replicating.
1. In the kafka-postgresql.tf file, specify these variables:
  - kf_source_endpoint_id: ID of the source endpoint.
  - transfer_enabled: 1 to create a target endpoint and transfer.
2. Make sure the Terraform configuration files are correct using this command:
  terraform validate
  If there are any errors in the configuration files, Terraform will point them out.
3. Create the required infrastructure:
  1. Run the command to view planned changes:
    
    terraform plan
    
    If the resource configuration descriptions are correct, the terminal will display a list of the resources to modify and their parameters. This is a test step. No resources are updated.
  2. If you are happy with the planned changes, apply them:
    
    Run the command:
    
    terraform apply
    
    Confirm the update of resources.
    
    Wait for the operation to complete.
4. The transfer will be activated automatically. Wait for its status to change to Replicating.

Test the transfer

Make sure the data from the topic in the source Managed Service for Apache Kafka® cluster is being moved to the Managed Service for PostgreSQL database:

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

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

To learn more about setting up an SSL certificate and working with kafkacat, see Connecting to a Apache Kafka® cluster from applications.

Make sure the data from the source Managed Service for Apache Kafka® cluster has been moved to the Managed Service for PostgreSQL database:
1. Connect to the Managed Service for PostgreSQL database.
2. Check that the sensors table contains the sent data:
```
SELECT * FROM sensors;
```

Delete the resources you created

Note

Before deleting the created resources, deactivate the transfer.

Some resources are not free of charge. To avoid paying for them, delete the resources you no longer need:

Delete the transfer.
Delete the source endpoint.
Delete the other resources depending on how they were created:
Manually

Terraform
1. In the terminal window, go to the directory containing the infrastructure plan.
2. Delete the kafka-postgresql.tf configuration file.
3. Make sure the Terraform configuration files are correct using this command:
  terraform validate
  If there are any errors in the configuration files, Terraform will point them out.
4. Confirm updating the resources.
  1. Run the command to view planned changes:
    
    terraform plan
    
    If the resource configuration descriptions are correct, the terminal will display a list of the resources to modify and their parameters. This is a test step. No resources are updated.
  2. If you are happy with the planned changes, apply them:
    
    Run the command:
    
    terraform apply
    
    Confirm the update of resources.
    
    Wait for the operation to complete.
  All the resources described in the kafka-postgresql.tf configuration file will be deleted.

Delivering data from an Apache Kafka® queue to PostgreSQL

Getting startedGetting started

Prepare the test dataPrepare the test data

Prepare and activate the transferPrepare and activate the transfer

Test the transferTest the transfer

Delete the resources you createdDelete the resources you created

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Getting started

Prepare the test data

Prepare and activate the transfer

Test the transfer

Delete the resources you created