Enabling idempotency still allows producing same message

Description

Hi,

Maybe I am getting the meaning/aim of idempotency in this library or Kafka in general. However, what I understand from the docs, code comments and other blog posts is that, enabling it (like show below) is meant to produce same message exactly once. Correct me if I am wrong please.

Technically, I am trying to produce same message exactly once.

Thanks

Note: I have seen this and this examples but they seem very complicated rather than keeping the producer and consumer in different files. To be honest, I am not even sure if they are applicable to me.

Versions

Sarama	Kafka	Go
v1.43.2	v3.3.2	1.22

Configuration

package main

import (
    "log"
    "time"

    "github.com/IBM/sarama"
)

func main() {
    cfg := sarama.NewConfig()
    cfg.ClientID = "test"
    cfg.Version = sarama.V3_3_2_0
    cfg.Producer.Return.Successes = true
    cfg.Producer.Retry.Max = 30
    cfg.Producer.Retry.Backoff = time.Millisecond * 10

    // Enable EOS (Exactly Once Semantic)
    cfg.Producer.Idempotent = true
    cfg.Producer.RequiredAcks = sarama.WaitForAll
    cfg.Net.MaxOpenRequests = 1
    //

    pro, err := sarama.NewSyncProducer([]string{":9093"}, cfg)
    if err != nil {
        log.Fatalln(err)
    }

    msg := sarama.ProducerMessage{
        Topic:     "warnings-topic", // This topic has only one partition
        Value:     sarama.StringEncoder("body"),
        Timestamp: time.Now(),
    }

    // Purposely simulating duplicate messages
    for i := 1; i <= 2; i++ {
        prt, off, err := pro.SendMessage(&msg)
        if err != nil {
            log.Fatalln(err)
        }

        log.Printf("I: %d PARTITION: %d OFFSET: %d\n", i, prt, off)
    }
}

$ go run -race main.go
2024/05/19 19:22:21 I: 1PARTITION: 0 OFFSET: 39841
2024/05/19 19:22:21 I: 2PARTITION: 0 OFFSET: 39842

Additional Context

IBM / sarama