How was the Outbox Pattern implemented? What tool was used to send from the outbox table to Kafka?

Outbox Pattern is a way to guarantee the atomicity of writing business data and messages for integration with other systems. A table called outbox is created in the database, where events to be sent to Kafka are recorded within a single transaction.

Implementation usually includes:

• Recording the event in the outbox table along with the main business operation within one transaction.
• A separate process or service that periodically reads new entries from the outbox, sends them to Kafka, and marks them as sent.

In Go, specialized libraries are often used or a custom service is written using the Kafka Producer API. To read and send messages from the outbox table, you can use:

• A cron job or daemon that polls the table.
• CDC (Change Data Capture) tools, such as Debezium, which track changes in the database and publish them to Kafka.

An example of simplified code for sending from outbox to Kafka in Go:

rows, _ := db.Query("SELECT id, payload FROM outbox WHERE sent = false")
for rows.Next() {
    var id int
    var payload string
    rows.Scan(&id, &payload)
    // Send to Kafka
    producer.Produce(&kafka.Message{TopicPartition: kafka.TopicPartition{Topic: &topic, Partition: kafka.PartitionAny}, Value: []byte(payload)}, nil)
    // Update status
    db.Exec("UPDATE outbox SET sent = true WHERE id = $1", id)
}