Fan-out Genesys Cloud EventBridge Presence Events to Kafka with Go

What You Will Build

• You will build a Go HTTP server that receives Genesys Cloud EventBridge presence events, verifies the payload signature, parses the event type, and routes the data to specific Kafka topics.
• This implementation uses the Genesys Cloud REST API for initial EventBridge configuration and the Confluent Kafka Go client for message dispatch.
• The tutorial covers Go 1.21 standard library, encoding/json, crypto/hmac, and github.com/confluentinc/confluent-kafka-go/kafka.

Prerequisites

• Genesys Cloud organization with EventBridge enabled and a public or NAT-routable endpoint for your Go server
• OAuth application configured with oauth:client_credentials and eventbridge:write scopes
• Go 1.21 or later installed
• Apache Kafka cluster accessible from the Go host
• Dependencies: go get github.com/confluentinc/confluent-kafka-go/kafka

Authentication Setup

Genesys Cloud EventBridge pushes events to HTTP endpoints. The push mechanism does not require OAuth for incoming requests, but you must authenticate to the Genesys Cloud API to register the endpoint. The following code demonstrates the client credentials OAuth flow to retrieve a bearer token.

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"time"
)

type OAuthTokenResponse struct {
	AccessToken string `json:"access_token"`
	TokenType   string `json:"token_type"`
	ExpiresIn   int    `json:"expires_in"`
	Scope       string `json:"scope"`
}

func GetGenesysOAuthToken(clientID, clientSecret, baseURL string) (string, error) {
	payload := map[string]string{
		"grant_type":    "client_credentials",
		"client_id":     clientID,
		"client_secret": clientSecret,
	}

	jsonPayload, err := json.Marshal(payload)
	if err != nil {
		return "", fmt.Errorf("failed to marshal OAuth payload: %w", err)
	}

	req, err := http.NewRequest("POST", fmt.Sprintf("%s/api/v2/oauth/token", baseURL), bytes.NewBuffer(jsonPayload))
	if err != nil {
		return "", fmt.Errorf("failed to create OAuth request: %w", err)
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Accept", "application/json")

	client := &http.Client{Timeout: 10 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return "", fmt.Errorf("OAuth request failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return "", fmt.Errorf("OAuth failed with status %d: %s", resp.StatusCode, string(body))
	}

	var tokenResp OAuthTokenResponse
	if err := json.NewDecoder(resp.Body).Decode(&tokenResp); err != nil {
		return "", fmt.Errorf("failed to decode OAuth response: %w", err)
	}

	return tokenResp.AccessToken, nil
}

This function returns a bearer token valid for 3600 seconds. Cache the token in memory and refresh it before expiration to avoid 401 Unauthorized errors on subsequent API calls.

Implementation

Step 1: Configure the EventBridge Endpoint via Genesys Cloud API

You must register your Go server URL with Genesys Cloud EventBridge before it will receive presence events. The following code creates an EventBridge endpoint that filters for presence events and assigns a shared secret for signature verification.

func RegisterEventBridgeEndpoint(token, baseURL, endpointURL, secret string) error {
	eventBridgePayload := map[string]interface{}{
		"name":        "Go Presence Router",
		"type":        "WEBHOOK",
		"enabled":     true,
		"url":         endpointURL,
		"secret":      secret,
		"eventTypes":  []string{"presence:state:changed", "presence:status:changed"},
		"retryPolicy": map[string]interface{}{"maxRetries": 3, "backoffMultiplier": 2},
	}

	jsonPayload, err := json.Marshal(eventBridgePayload)
	if err != nil {
		return fmt.Errorf("failed to marshal EventBridge payload: %w", err)
	}

	req, err := http.NewRequest("POST", fmt.Sprintf("%s/api/v2/analytics/events/eventbridges", baseURL), bytes.NewBuffer(jsonPayload))
	if err != nil {
		return fmt.Errorf("failed to create EventBridge request: %w", err)
	}

	req.Header.Set("Authorization", "Bearer "+token)
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Accept", "application/json")

	client := &http.Client{Timeout: 15 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return fmt.Errorf("EventBridge registration failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode == http.StatusTooManyRequests {
		retryAfter := resp.Header.Get("Retry-After")
		fmt.Printf("Rate limited by Genesys Cloud. Retry after %s seconds.\n", retryAfter)
		return fmt.Errorf("429 rate limit exceeded")
	}

	if resp.StatusCode != http.StatusCreated && resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("EventBridge registration failed with status %d: %s", resp.StatusCode, string(body))
	}

	return nil
}

The eventTypes array restricts the push to presence changes only. The secret field enables HMAC-SHA256 signature verification. Store this secret securely. It will be used to validate incoming webhook requests.

Step 2: Build the Go HTTP Router and Verify Event Signatures

Genesys Cloud attaches an X-Genesys-Event-Signature header to every push request. Your router must verify this signature before processing the payload. The following handler implements verification and returns appropriate HTTP status codes.

func HandleEventBridge(secret string, kafkaProducer *kafka.Producer) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost {
			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
			return
		}

		signature := r.Header.Get("X-Genesys-Event-Signature")
		if signature == "" {
			http.Error(w, "Missing signature header", http.StatusBadRequest)
			return
		}

		body, err := io.ReadAll(r.Body)
		if err != nil {
			http.Error(w, "Failed to read request body", http.StatusInternalServerError)
			return
		}
		defer r.Body.Close()

		mac := hmac.New(sha256.New, []byte(secret))
		mac.Write(body)
		expectedSignature := fmt.Sprintf("%x", mac.Sum(nil))

		if !hmac.Equal([]byte(signature), []byte(expectedSignature)) {
			http.Error(w, "Invalid signature", http.StatusForbidden)
			return
		}

		var event GenesysPresenceEvent
		if err := json.Unmarshal(body, &event); err != nil {
			http.Error(w, "Invalid JSON payload", http.StatusBadRequest)
			return
		}

		topic, err := getRoutingTopic(event)
		if err != nil {
			http.Error(w, fmt.Sprintf("Routing error: %v", err), http.StatusNotFound)
			return
		}

		if err := publishToKafka(kafkaProducer, topic, &event); err != nil {
			http.Error(w, fmt.Sprintf("Kafka publish failed: %v", err), http.StatusServiceUnavailable)
			return
		}

		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusOK)
		json.NewEncoder(w).Encode(map[string]string{"status": "processed"})
	}
}

The handler reads the raw body, computes the HMAC-SHA256 hash, and compares it against the header using constant-time comparison. If verification fails, the router returns 403 Forbidden. This prevents replay attacks and unauthorized payload injection.

Step 3: Parse Presence Payloads and Apply Dynamic Routing Rules

Genesys Cloud presence events follow a consistent structure. You must extract the event type and apply dynamic routing rules to determine the target Kafka topic. The following code defines the event structure and routing logic.

type GenesysPresenceEvent struct {
	ID          string                 `json:"id"`
	EventType   string                 `json:"eventType"`
	Timestamp   int64                  `json:"timestamp"`
	Source      string                 `json:"source"`
	Attributes  map[string]interface{} `json:"attributes"`
}

var routingRules = map[string]string{
	"presence:state:changed":    "gen-presence-state",
	"presence:status:changed":   "gen-presence-status",
	"presence:location:changed": "gen-presence-location",
}

func getRoutingTopic(event GenesysPresenceEvent) (string, error) {
	topic, exists := routingRules[event.EventType]
	if !exists {
		return "", fmt.Errorf("unsupported event type: %s", event.EventType)
	}
	return topic, nil
}

The routingRules map acts as a configuration layer. You can load this map from environment variables, a YAML file, or a configuration service to make the router dynamic without restarting the Go binary. The function returns an error for unrecognized event types, which triggers a 404 response to Genesys Cloud, causing EventBridge to drop the message and log a delivery failure.

Step 4: Dispatch to Kafka Topics with Retry Logic

Kafka producers can fail due to broker unavailability, network partitions, or topic authorization errors. The following implementation uses the Confluent Kafka Go client with asynchronous delivery and exponential backoff retry logic for transient failures.

func publishToKafka(producer *kafka.Producer, topic string, event *GenesysPresenceEvent) error {
	payload, err := json.Marshal(event)
	if err != nil {
		return fmt.Errorf("failed to marshal event for Kafka: %w", err)
	}

	message := &kafka.Message{
		TopicPartition: kafka.TopicPartition{Topic: &topic, Partition: kafka.PartitionAny},
		Value:          payload,
		Key:            []byte(event.ID),
	}

	deliveryChan := make(chan kafka.Event, 1)
	err = producer.Produce(message, deliveryChan)
	if err != nil {
		return fmt.Errorf("Kafka produce failed: %w", err)
	}

	ev := <-deliveryChan
	msg := ev.(*kafka.Message)
	if msg.TopicPartition.Error != nil {
		if err := msg.TopicPartition.Error; err != nil {
			if isTransientKafkaError(err) {
				return retryKafkaPublish(producer, topic, event, 3)
			}
			return fmt.Errorf("Kafka delivery failed: %w", err)
		}
	}

	return nil
}

func isTransientKafkaError(err error) bool {
	if err == nil {
		return false
	}
	errStr := err.Error()
	return strings.Contains(errStr, "Local: Broker transport failure") ||
		strings.Contains(errStr, "Local: Timed out") ||
		strings.Contains(errStr, "Local: Leader not available")
}

func retryKafkaPublish(producer *kafka.Producer, topic string, event *GenesysPresenceEvent, maxRetries int) error {
	for i := 0; i < maxRetries; i++ {
		backoff := time.Duration(1<<uint(i)) * 500 * time.Millisecond
		time.Sleep(backoff)

		payload, _ := json.Marshal(event)
		message := &kafka.Message{
			TopicPartition: kafka.TopicPartition{Topic: &topic, Partition: kafka.PartitionAny},
			Value:          payload,
			Key:            []byte(event.ID),
		}

		deliveryChan := make(chan kafka.Event, 1)
		if err := producer.Produce(message, deliveryChan); err == nil {
			ev := <-deliveryChan
			if msg, ok := ev.(*kafka.Message); ok && msg.TopicPartition.Error == nil {
				return nil
			}
		}
	}
	return fmt.Errorf("Kafka publish failed after %d retries", maxRetries)
}

The retryKafkaPublish function implements exponential backoff starting at 500 milliseconds. It only retries on transient broker errors. Permanent errors such as UnknownTopicOrPartition or AuthorizationFailed fail immediately to prevent infinite loops.

Complete Working Example

The following file combines all components into a single executable Go application. Replace the placeholder configuration values with your environment credentials before running.

package main

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"strings"
	"time"

	"github.com/confluentinc/confluent-kafka-go/kafka"
)

type GenesysPresenceEvent struct {
	ID         string                 `json:"id"`
	EventType  string                 `json:"eventType"`
	Timestamp  int64                  `json:"timestamp"`
	Source     string                 `json:"source"`
	Attributes map[string]interface{} `json:"attributes"`
}

var routingRules = map[string]string{
	"presence:state:changed":    "gen-presence-state",
	"presence:status:changed":   "gen-presence-status",
	"presence:location:changed": "gen-presence-location",
}

func getRoutingTopic(event GenesysPresenceEvent) (string, error) {
	topic, exists := routingRules[event.EventType]
	if !exists {
		return "", fmt.Errorf("unsupported event type: %s", event.EventType)
	}
	return topic, nil
}

func HandleEventBridge(secret string, kafkaProducer *kafka.Producer) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost {
			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
			return
		}

		signature := r.Header.Get("X-Genesys-Event-Signature")
		if signature == "" {
			http.Error(w, "Missing signature header", http.StatusBadRequest)
			return
		}

		body, err := io.ReadAll(r.Body)
		if err != nil {
			http.Error(w, "Failed to read request body", http.StatusInternalServerError)
			return
		}
		defer r.Body.Close()

		mac := hmac.New(sha256.New, []byte(secret))
		mac.Write(body)
		expectedSignature := fmt.Sprintf("%x", mac.Sum(nil))

		if !hmac.Equal([]byte(signature), []byte(expectedSignature)) {
			http.Error(w, "Invalid signature", http.StatusForbidden)
			return
		}

		var event GenesysPresenceEvent
		if err := json.Unmarshal(body, &event); err != nil {
			http.Error(w, "Invalid JSON payload", http.StatusBadRequest)
			return
		}

		topic, err := getRoutingTopic(event)
		if err != nil {
			http.Error(w, fmt.Sprintf("Routing error: %v", err), http.StatusNotFound)
			return
		}

		if err := publishToKafka(kafkaProducer, topic, &event); err != nil {
			http.Error(w, fmt.Sprintf("Kafka publish failed: %v", err), http.StatusServiceUnavailable)
			return
		}

		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusOK)
		json.NewEncoder(w).Encode(map[string]string{"status": "processed"})
	}
}

func publishToKafka(producer *kafka.Producer, topic string, event *GenesysPresenceEvent) error {
	payload, err := json.Marshal(event)
	if err != nil {
		return fmt.Errorf("failed to marshal event for Kafka: %w", err)
	}

	message := &kafka.Message{
		TopicPartition: kafka.TopicPartition{Topic: &topic, Partition: kafka.PartitionAny},
		Value:          payload,
		Key:            []byte(event.ID),
	}

	deliveryChan := make(chan kafka.Event, 1)
	err = producer.Produce(message, deliveryChan)
	if err != nil {
		return fmt.Errorf("Kafka produce failed: %w", err)
	}

	ev := <-deliveryChan
	msg := ev.(*kafka.Message)
	if msg.TopicPartition.Error != nil {
		if isTransientKafkaError(msg.TopicPartition.Error) {
			return retryKafkaPublish(producer, topic, event, 3)
		}
		return fmt.Errorf("Kafka delivery failed: %w", msg.TopicPartition.Error)
	}

	return nil
}

func isTransientKafkaError(err error) bool {
	if err == nil {
		return false
	}
	errStr := err.Error()
	return strings.Contains(errStr, "Local: Broker transport failure") ||
		strings.Contains(errStr, "Local: Timed out") ||
		strings.Contains(errStr, "Local: Leader not available")
}

func retryKafkaPublish(producer *kafka.Producer, topic string, event *GenesysPresenceEvent, maxRetries int) error {
	for i := 0; i < maxRetries; i++ {
		backoff := time.Duration(1<<uint(i)) * 500 * time.Millisecond
		time.Sleep(backoff)

		payload, _ := json.Marshal(event)
		message := &kafka.Message{
			TopicPartition: kafka.TopicPartition{Topic: &topic, Partition: kafka.PartitionAny},
			Value:          payload,
			Key:            []byte(event.ID),
		}

		deliveryChan := make(chan kafka.Event, 1)
		if err := producer.Produce(message, deliveryChan); err == nil {
			ev := <-deliveryChan
			if msg, ok := ev.(*kafka.Message); ok && msg.TopicPartition.Error == nil {
				return nil
			}
		}
	}
	return fmt.Errorf("Kafka publish failed after %d retries", maxRetries)
}

func main() {
	secret := os.Getenv("GENESYS_WEBHOOK_SECRET")
	if secret == "" {
		log.Fatal("GENESYS_WEBHOOK_SECRET environment variable is required")
	}

	kafkaBrokers := os.Getenv("KAFKA_BROKERS")
	if kafkaBrokers == "" {
		log.Fatal("KAFKA_BROKERS environment variable is required")
	}

	producer, err := kafka.NewProducer(&kafka.ConfigMap{
		"bootstrap.servers": kafkaBrokers,
		"acks":              "all",
		"retries":           3,
		"retry.backoff.ms":  200,
	})
	if err != nil {
		log.Fatalf("Failed to create Kafka producer: %v", err)
	}
	defer producer.Close()

	http.HandleFunc("/eventbridge/presence", HandleEventBridge(secret, producer))

	log.Println("Starting Genesys Cloud EventBridge Presence Router on :8080")
	if err := http.ListenAndServe(":8080", nil); err != nil {
		log.Fatalf("HTTP server failed: %v", err)
	}
}

Run the application with go run main.go. Ensure the GENESYS_WEBHOOK_SECRET and KAFKA_BROKERS environment variables are set. The server listens on port 8080 and exposes the /eventbridge/presence endpoint for Genesys Cloud EventBridge configuration.

Common Errors & Debugging

Error: 403 Forbidden on Webhook Delivery

• Cause: The HMAC signature verification failed. The secret stored in your Go application does not match the secret configured in the Genesys Cloud EventBridge endpoint.
• Fix: Verify the GENESYS_WEBHOOK_SECRET environment variable matches the secret field in the EventBridge configuration. Ensure no trailing whitespace exists in the environment variable.
• Code showing the fix: Log the raw signature and computed signature during development to compare byte-for-byte differences.

Error: 429 Too Many Requests on EventBridge Registration

• Cause: Genesys Cloud API enforces rate limits on configuration endpoints. Excessive polling or rapid retry loops trigger 429 responses.
• Fix: Implement exponential backoff when calling RegisterEventBridgeEndpoint. Read the Retry-After header and sleep accordingly.
• Code showing the fix: The RegisterEventBridgeEndpoint function checks resp.StatusCode == http.StatusTooManyRequests and logs the Retry-After value. Wrap the call in a retry loop with time.Sleep before re-attempting.

Error: Kafka Broker Transport Failure

• Cause: Network partition, DNS resolution failure, or Kafka broker downtime.
• Fix: Verify KAFKA_BROKERS points to the correct bootstrap servers. Check firewall rules and TLS configuration if using security.protocol=SASL_SSL. The retryKafkaPublish function already handles transient failures with backoff.
• Code showing the fix: Add log.Printf("Kafka retry attempt %d/%d", i+1, maxRetries) inside the retry loop to track delivery attempts in production logs.

Error: 400 Bad Request on Payload Parsing

• Cause: Genesys Cloud sent a malformed JSON payload or the event type changed unexpectedly.
• Fix: Validate the eventType field against routingRules before routing. Return 400 with a descriptive message to trigger Genesys Cloud retry policies.
• Code showing the fix: The getRoutingTopic function returns an error for unsupported types, which the HTTP handler catches and returns 404. Change to 400 if you want Genesys Cloud to drop the message permanently.

Official References

• Genesys Cloud EventBridge API Documentation
• Genesys Cloud OAuth 2.0 Client Credentials Flow
• Confluent Kafka Go Client Documentation
• Genesys Cloud Presence Event Schema