inlet/kafka: use exporter as a key for Kafka

Otherwise, messages are reaching the outlet unordered and missing IPFIX
templates may make more flows lost. Moreover, when using several
outlets, some of them may not get the templates.

console/data/docs/99-changelog.md

@@ -15,6 +15,7 @@ identified with a specific icon:
 - 💥 *config*: `skip-verify` is false by default in TLS configurations for
   ClickHouse, Kafka and remote data sources (previously, `verify` was set to
   false by default)
+- 🩹 *inlet*: keep flows from one exporter into a single partition
 - 🩹 *outlet*: provide additional gracetime for a worker to send to ClickHouse
 - 🩹 *outlet*: prevent discarding flows on shutdown
 - 🩹 *outlet*: enhance scaling up and down workers to avoid hysteresis

inlet/kafka/root.go

@@ -6,9 +6,7 @@ package kafka
 
 import (
 	"context"
-	"encoding/binary"
 	"fmt"
-	"math/rand/v2"
 	"strings"
 	"time"
 
@@ -109,11 +107,9 @@ func (c *Component) Stop() error {
 
 // Send a message to Kafka.
 func (c *Component) Send(exporter string, payload []byte, finalizer func()) {
-	key := make([]byte, 4)
-	binary.BigEndian.PutUint32(key, rand.Uint32())
 	record := &kgo.Record{
 		Topic: c.kafkaTopic,
-		Key:   key,
+		Key:   []byte(exporter),
 		Value: payload,
 	}
 	c.kafkaClient.Produce(context.Background(), record, func(r *kgo.Record, err error) {