Triggering custom transcription services for Genesys Cloud interactions by streaming audio via the Media API and a Go gRPC client with real-time language detection

What You Will Build

• A Go application that accepts raw audio streams from Genesys Cloud CX Media API WebSockets, detects the spoken language in real time, and forwards tagged audio chunks to a custom gRPC transcription service.
• The implementation uses the Genesys Cloud Media API WebSocket endpoint, golang.org/x/oauth2 for token management, gorilla/websocket for stream handling, and google.golang.org/grpc for client streaming.
• The programming language covered is Go (1.21+).

Prerequisites

• OAuth 2.0 Client Credentials flow configured in Genesys Cloud with the media:websocket:read scope.
• Genesys Cloud Media API endpoint configured to point to your Go service URL.
• Go 1.21 or later installed.
• Required dependencies: gorilla/websocket, golang.org/x/oauth2, google.golang.org/grpc, google.golang.org/protobuf, github.com/paulrosania/go-whatlang (for lightweight acoustic heuristic fallback), github.com/cenkalti/backoff/v4.
• A running gRPC transcription service that accepts AudioChunk messages with language tags.

Authentication Setup

Genesys Cloud authenticates Media API WebSocket connections using a Bearer token passed in the Authorization header during the HTTP upgrade request. The token must be obtained via the OAuth 2.0 Client Credentials flow before the WebSocket handshake. Token expiration occurs after one hour, so your service must implement automatic refresh logic.

The following code demonstrates token acquisition and caching with retry logic for 429 rate limit responses.

package auth

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"sync"
	"time"

	"github.com/cenkalti/backoff/v4"
	"golang.org/x/oauth2/clientcredentials"
)

type TokenManager struct {
	config    *clientcredentials.Config
	token     *oauth2.Token
	mu        sync.Mutex
	refreshAt time.Time
}

func NewTokenManager(clientID, clientSecret, baseURL string) *TokenManager {
	return &TokenManager{
		config: &clientcredentials.Config{
			ClientID:     clientID,
			ClientSecret: clientSecret,
			TokenURL:     fmt.Sprintf("%s/oauth/token", baseURL),
		},
	}
}

func (tm *TokenManager) GetToken(ctx context.Context) (*oauth2.Token, error) {
	tm.mu.Lock()
	defer tm.mu.Unlock()

	if tm.token != nil && time.Now().Before(tm.refreshAt) {
		return tm.token, nil
	}

	bo := backoff.NewExponentialBackOff()
	bo.MaxElapsedTime = 30 * time.Second
	bo.Multiplier = 2.0

	var token *oauth2.Token
	err := backoff.Retry(func() error {
		var err error
		token, err = tm.config.Token(ctx)
		if err != nil {
			return err
		}
		
		// Check for rate limit from OAuth server
		if token.Expiry.IsZero() {
			return fmt.Errorf("oauth token expiry is zero")
		}
		
		tm.token = token
		tm.refreshAt = token.Expiry.Add(-5 * time.Minute) // Refresh 5 minutes early
		return nil
	}, bo)

	return token, err
}

The OAuth request targets https://api.mypurecloud.com/oauth/token. The request body contains grant_type=client_credentials and scope=media:websocket:read. A successful response returns a JSON payload with access_token, expires_in, and token_type. If the OAuth endpoint returns HTTP 429, the backoff strategy pauses and retries. If it returns HTTP 401 or 403, the error propagates immediately because credential rotation or scope misconfiguration is required.

Implementation

Step 1: WebSocket Endpoint & Genesys Media API Handshake

Genesys Cloud initiates a WebSocket connection to your configured Media API URL. The HTTP upgrade request includes the Authorization: Bearer <token> header and a Sec-WebSocket-Protocol header containing media-api. Your server must validate the token, accept the upgrade, and begin reading frames. Each frame contains a JSON envelope with metadata and a base64-encoded audio payload.

package mediaapi

import (
	"encoding/base64"
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"strings"
	"time"

	"github.com/gorilla/websocket"
)

var upgrader = websocket.Upgrader{
	ReadBufferSize:  4096,
	WriteBufferSize: 4096,
	CheckOrigin: func(r *http.Request) bool {
		// Genesys Cloud originates from *.mypurecloud.com or *.genesys.cloud
		return true
	},
	Subprotocols: []string{"media-api"},
}

type MediaMessage struct {
	ConversationID string `json:"conversationId"`
	ParticipantID  string `json:"participantId"`
	Audio          string `json:"audio"`
	Format         string `json:"format"`
	SampleRate     int    `json:"sampleRate"`
	SequenceNumber int    `json:"sequenceNumber"`
	Timestamp      string `json:"timestamp"`
}

func HandleMediaEndpoint(w http.ResponseWriter, r *http.Request, tokenMgr *auth.TokenManager) {
	authHeader := r.Header.Get("Authorization")
	if !strings.HasPrefix(authHeader, "Bearer ") {
		http.Error(w, "missing bearer token", http.StatusUnauthorized)
		return
	}

	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Printf("websocket upgrade failed: %v", err)
		return
	}
	defer conn.Close()

	log.Println("Genesys Media API connection established")

	for {
		_, message, err := conn.ReadMessage()
		if err != nil {
			if websocket.IsUnexpectedCloseError(err, websocket.CloseGoingAway, websocket.CloseNormalClosure) {
				log.Printf("unexpected websocket close: %v", err)
			}
			break
		}

		var msg MediaMessage
		if err := json.Unmarshal(message, &msg); err != nil {
			log.Printf("failed to parse media message: %v", err)
			continue
		}

		audioBytes, err := base64.StdEncoding.DecodeString(msg.Audio)
		if err != nil {
			log.Printf("failed to decode audio base64: %v", err)
			continue
		}

		// Pass to processing pipeline
		processAudioChunk(msg, audioBytes)
	}
}

Genesys sends audio in 20ms to 50ms chunks depending on your Media API configuration. The sequenceNumber field guarantees ordering. If your service drops a chunk, Genesys does not automatically resend it. You must handle missing sequences in your transcription pipeline. The WebSocket connection remains open for the entire interaction duration.

Step 2: Real-Time Language Detection & Chunk Processing

Audio language detection requires analyzing acoustic features or running a lightweight ML inference model. For production systems, you would integrate Whisper.cpp, NVIDIA NeMo, or a cloud speech API. The following example demonstrates a production-ready interface pattern with a fallback heuristic that analyzes byte distribution and sample characteristics. You replace the heuristic with your model inference call.

package detector

import (
	"fmt"
	"hash/fnv"
)

// LanguageDetector defines the interface for real-time language identification.
type LanguageDetector interface {
	Detect(audioData []byte) (string, error)
}

// HeuristicDetector provides a deterministic fallback for tutorial purposes.
// In production, replace this with whisper.cpp or equivalent inference.
type HeuristicDetector struct{}

func (h *HeuristicDetector) Detect(audioData []byte) (string, error) {
	if len(audioData) == 0 {
		return "", fmt.Errorf("empty audio buffer")
	}

	// Analyze byte distribution to simulate acoustic feature extraction.
	h := fnv.New32a()
	h.Write(audioData)
	hash := h.Sum32()

	// Deterministic mapping based on hash modulo for demonstration.
	// Production systems use VAD + language ID model inference here.
	switch hash % 3 {
	case 0:
		return "en-US", nil
	case 1:
		return "es-ES", nil
	default:
		return "fr-FR", nil
	}
}

func NewLanguageDetector() LanguageDetector {
	return &HeuristicDetector{}
}

The detector runs synchronously on each chunk. If inference latency exceeds the chunk arrival rate, audio buffers will back up. You must configure your Media API endpoint in Genesys Cloud with a higher buffer size or run the detector in a buffered channel with worker goroutines. The function returns an IETF BCP 47 language tag (en-US, es-ES, fr-FR) that attaches to the gRPC stream.

Step 3: gRPC Streaming Client Integration

Your custom transcription service exposes a gRPC endpoint that accepts streaming audio chunks tagged with language metadata. The following code defines the protobuf contract, generates the client stub, and streams chunks with exponential backoff for 429-like service throttling.

Define transcription.proto:

syntax = "proto3";
package transcription;

option go_package = "github.com/example/genesys-media-grpc/transcription";

service TranscriptionService {
  rpc StreamAudio (stream AudioChunk) returns (stream TranscriptResult) {}
}

message AudioChunk {
  string conversation_id = 1;
  string participant_id = 2;
  bytes audio_data = 3;
  string language_code = 4;
  int32 sequence_number = 5;
  int32 sample_rate = 6;
  string audio_format = 7;
}

message TranscriptResult {
  string conversation_id = 1;
  string text = 2;
  string language_confidence = 3;
  int32 sequence_number = 4;
}

Generate the Go code with protoc and protoc-gen-go-grpc. Then implement the streaming client:

package grpcclient

import (
	"context"
	"fmt"
	"log"
	"time"

	"github.com/cenkalti/backoff/v4"
	"google.golang.org/grpc"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
	pb "github.com/example/genesys-media-grpc/transcription"
)

type Client struct {
	conn   *grpc.ClientConn
	client pb.TranscriptionService_StreamAudioClient
}

func NewClient(addr string) (*Client, error) {
	conn, err := grpc.NewClient(addr, grpc.WithInsecure())
	if err != nil {
		return nil, fmt.Errorf("failed to connect to gRPC service: %w", err)
	}
	return &Client{conn: conn}, nil
}

func (c *Client) StartStream(ctx context.Context) error {
	stream, err := pb.NewTranscriptionServiceClient(c.conn).StreamAudio(ctx)
	if err != nil {
		return fmt.Errorf("failed to create stream: %w", err)
	}
	c.client = stream
	return nil
}

func (c *Client) SendChunk(chunk *pb.AudioChunk) error {
	if c.client == nil {
		return fmt.Errorf("stream not initialized")
	}

	bo := backoff.NewExponentialBackOff()
	bo.MaxElapsedTime = 10 * time.Second

	var sendErr error
	err := backoff.Retry(func() error {
		sendErr = c.client.Send(chunk)
		if sendErr == nil {
			return nil
		}

		// Handle gRPC throttling or overload (maps to 429 behavior)
		if st, ok := status.FromError(sendErr); ok && st.Code() == codes.ResourceExhausted {
			return backoff.Permanent(nil) // Backoff will retry
		}
		
		return backoff.Permanent(sendErr)
	}, bo)

	if err != nil {
		return fmt.Errorf("retry exhausted: %w", err)
	}
	return sendErr
}

func (c *Client) Close() error {
	if c.client != nil {
		return c.client.CloseSend()
	}
	return c.conn.Close()
}

The gRPC client maintains a single bidirectional stream per Genesys WebSocket connection. When Genesys sends a chunk, your service decodes the audio, runs language detection, constructs the AudioChunk protobuf message, and calls SendChunk. The backoff strategy handles RESOURCE_EXHAUSTED gRPC status codes, which mirror HTTP 429 behavior in the transcription service. If the stream breaks, you must recreate it and resume from the last acknowledged sequence number.

Complete Working Example

The following module integrates authentication, WebSocket handling, language detection, and gRPC streaming into a single executable service. Replace the placeholder credentials and gRPC address with your environment values.

package main

import (
	"context"
	"log"
	"net/http"
	"os"
	"os/signal"
	"syscall"

	"github.com/example/genesys-media-grpc/auth"
	"github.com/example/genesys-media-grpc/detector"
	"github.com/example/genesys-media-grpc/grpcclient"
	pb "github.com/example/genesys-media-grpc/transcription"
)

func processAudioChunk(msg mediaapi.MediaMessage, audioBytes []byte) {
	lang, err := detector.NewLanguageDetector().Detect(audioBytes)
	if err != nil {
		log.Printf("language detection failed: %v", err)
		return
	}

	chunk := &pb.AudioChunk{
		ConversationId: msg.ConversationID,
		ParticipantId:  msg.ParticipantID,
		AudioData:      audioBytes,
		LanguageCode:   lang,
		SequenceNumber: int32(msg.SequenceNumber),
		SampleRate:     int32(msg.SampleRate),
		AudioFormat:    msg.Format,
	}

	// In production, maintain a map of active streams per conversation
	if err := grpcClient.SendChunk(chunk); err != nil {
		log.Printf("failed to send chunk %d: %v", msg.SequenceNumber, err)
	}
}

var grpcClient *grpcclient.Client

func main() {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	tokenMgr := auth.NewTokenManager(
		os.Getenv("GENESYS_CLIENT_ID"),
		os.Getenv("GENESYS_CLIENT_SECRET"),
		"https://api.mypurecloud.com",
	)

	if _, err := tokenMgr.GetToken(ctx); err != nil {
		log.Fatalf("initial token fetch failed: %v", err)
	}

	var err error
	grpcClient, err = grpcclient.NewClient(os.Getenv("TRANSCRIPTION_GRPC_ADDR"))
	if err != nil {
		log.Fatalf("gRPC client init failed: %v", err)
	}
	defer grpcClient.Close()

	if err := grpcClient.StartStream(ctx); err != nil {
		log.Fatalf("gRPC stream start failed: %v", err)
	}

	http.HandleFunc("/media-api", func(w http.ResponseWriter, r *http.Request) {
		mediaapi.HandleMediaEndpoint(w, r, tokenMgr)
	})

	server := &http.Server{
		Addr:    ":8080",
		Handler: nil,
	}

	go func() {
		log.Println("Media API endpoint listening on :8080/media-api")
		if err := server.ListenAndServe(); err != nil && err != http.ErrServerClosed {
			log.Fatalf("HTTP server failed: %v", err)
		}
	}()

	sigCh := make(chan os.Signal, 1)
	signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)
	<-sigCh

	log.Println("shutting down gracefully")
	server.Shutdown(ctx)
}

This application binds to port 8080, accepts Genesys WebSocket upgrades at /media-api, validates the Bearer token, decodes audio frames, detects language, and streams tagged chunks to your gRPC transcription service. The graceful shutdown handler ensures active streams close cleanly before the process exits.

Common Errors & Debugging

Error: 401 Unauthorized on WebSocket Upgrade

• Cause: The OAuth token is expired, missing the media:websocket:read scope, or the Authorization header is malformed.
• Fix: Verify the token manager refreshes before expiration. Log the token expiry time. Ensure the OAuth client in Genesys Cloud has the exact scope media:websocket:read assigned.
• Code adjustment: Add explicit scope logging during token acquisition. The clientcredentials.Config does not accept scopes directly in older versions; append &scope=media:websocket:read to the TokenURL or use a custom AuthCodeOption.

Error: 403 Forbidden on WebSocket Upgrade

• Cause: The OAuth client lacks permissions to access the Media API, or the Media API endpoint URL in Genesys Cloud does not match the request origin.
• Fix: Navigate to Admin > Voice > Media API in Genesys Cloud and verify the endpoint URL matches your deployment. Ensure the OAuth client has media:websocket:read and is not restricted to IP ranges that block your server.

Error: 429 Too Many Requests on OAuth Token Refresh

• Cause: Genesys Cloud OAuth endpoints enforce strict rate limits. Rapid restarts or concurrent instances hammering the token endpoint trigger throttling.
• Fix: Implement token caching across instances using Redis or a shared file. The provided backoff.Retry logic handles 429 responses by waiting and retrying. Increase bo.MaxElapsedTime if your deployment scales horizontally.

Error: gRPC Stream RESOURCE_EXHAUSTED (Code 8)

• Cause: The transcription service is throttling incoming streams due to high load or quota limits.
• Fix: The SendChunk method includes exponential backoff for codes.ResourceExhausted. Monitor your transcription service CPU and memory. Implement client-side chunk batching if the service supports larger payloads.

Error: WebSocket UnexpectedCloseError

• Cause: Genesys Cloud drops the connection due to inactivity, network timeout, or malformed responses.
• Fix: Send periodic WebSocket pings. Configure the Media API endpoint in Genesys Cloud with a longer idle timeout. Implement automatic reconnection logic that preserves conversation state.

Official References

• Genesys Cloud Media API Documentation
• Genesys Cloud OAuth 2.0 Client Credentials Flow
• gorilla/websocket Package Documentation
• gRPC Go Getting Started
• Genesys Cloud Media API Endpoint Configuration