Downloading NICE CXone Outbound Campaign Call Recordings with Go

What You Will Build

• A Go module that fetches outbound campaign recording artifacts, validates batch limits and retention policies, retrieves presigned URLs, handles format verification, triggers cache invalidation, logs audit trails, and synchronizes with external archives via webhooks.
• This uses the NICE CXone Outbound Campaign API v2 and standard Go net/http client patterns.
• The programming language covered is Go 1.21+.

Prerequisites

• OAuth client credentials with outbound:recordingartifact:read and outbound:campaign:read scopes
• CXone API v2 base URL: https://api.nicecxone.com
• Go 1.21+ runtime
• Standard library dependencies: net/http, encoding/json, time, sync, log/slog, os, io, fmt, context, math, syscall

Authentication Setup

CXone uses standard OAuth 2.0 client credentials flow. The token endpoint issues short-lived access tokens that require refresh logic before expiration.

package main

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

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

type TokenManager struct {
	clientID     string
	clientSecret string
	tokenURL     string
	httpClient   *http.Client
	mu           sync.Mutex
	token        string
	expiresAt    time.Time
}

func NewTokenManager(clientID, clientSecret string) *TokenManager {
	return &TokenManager{
		clientID:     clientID,
		clientSecret: clientSecret,
		tokenURL:     "https://api.nicecxone.com/oauth/token",
		httpClient:   &http.Client{Timeout: 10 * time.Second},
	}
}

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

	if tm.token != "" && time.Now().Before(tm.expiresAt.Add(-30*time.Second)) {
		return tm.token, nil
	}

	payload := fmt.Sprintf(
		"grant_type=client_credentials&client_id=%s&client_secret=%s&scope=outbound:recordingartifact:read+outbound:campaign:read",
		tm.clientID, tm.clientSecret,
	)

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, tm.tokenURL, bytes.NewBufferString(payload))
	if err != nil {
		return "", fmt.Errorf("failed to create token request: %w", err)
	}
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")

	resp, err := tm.httpClient.Do(req)
	if err != nil {
		return "", fmt.Errorf("token request failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("token endpoint returned %d", resp.StatusCode)
	}

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

	tm.token = tr.AccessToken
	tm.expiresAt = time.Now().Add(time.Duration(tr.ExpiresIn) * time.Second)
	return tm.token, nil
}

OAuth Scope Requirement: outbound:recordingartifact:read is mandatory for all recording artifact operations. The token request must include this scope in the client_credentials grant.

Implementation

Step 1: Construct Download Payloads and Validate Batch Limits

CXone outbound recording downloads require explicit schema validation before execution. The payload must include a recording reference, media matrix configuration, and fetch directive. Batch operations are strictly limited to 50 artifacts per request to prevent memory exhaustion and API throttling.

type FetchDirective struct {
	Format       string `json:"format"`
	IncludeMedia bool   `json:"include_media"`
}

type MediaMatrix struct {
	Channels   []int `json:"channels"`
	SampleRate int   `json:"sample_rate"`
}

type DownloadPayload struct {
	RecordingReference string         `json:"recording_reference"`
	MediaMatrix        MediaMatrix    `json:"media_matrix"`
	FetchDirective     FetchDirective `json:"fetch_directive"`
}

func ValidateDownloadPayload(payloads []DownloadPayload, maxBatch int) error {
	if len(payloads) == 0 {
		return fmt.Errorf("payload array cannot be empty")
	}
	if len(payloads) > maxBatch {
		return fmt.Errorf("batch size %d exceeds maximum limit of %d", len(payloads), maxBatch)
	}

	for i, p := range payloads {
		if p.RecordingReference == "" {
			return fmt.Errorf("payload[%d]: recording_reference is required", i)
		}
		if p.FetchDirective.Format == "" {
			return fmt.Errorf("payload[%d]: fetch_directive.format is required", i)
		}
		if p.MediaMatrix.SampleRate <= 0 {
			return fmt.Errorf("payload[%d]: media_matrix.sample_rate must be positive", i)
		}
	}
	return nil
}

HTTP Request/Response Cycle:

POST /api/v2/outbound/recordingartifacts/batch/validate HTTP/1.1
Host: api.nicecxone.com
Authorization: Bearer <ACCESS_TOKEN>
Content-Type: application/json

{
  "payloads": [
    {
      "recording_reference": "OUT-2024-8834-REC",
      "media_matrix": {
        "channels": [0, 1],
        "sample_rate": 8000
      },
      "fetch_directive": {
        "format": "wav",
        "include_media": true
      }
    }
  ]
}

HTTP/1.1 200 OK
Content-Type: application/json

{
  "validation_status": "passed",
  "batch_limit_applied": 50,
  "estimated_size_bytes": 4194304
}

Step 2: Execute Retention Policy and Access Authorization Pipelines

Before initiating downloads, the system must verify retention compliance and role-based access. CXone stores retention metadata on each artifact. Expired artifacts return 410 Gone on download attempts.

type ArtifactMetadata struct {
	ID             string `json:"id"`
	Format         string `json:"format"`
	RetentionPolicy string `json:"retention_policy"`
	ExpiryDate     string `json:"expiry_date"`
	AccessLevel    string `json:"access_level"`
	DownloadURL    string `json:"download_url"`
}

func ValidateRetentionAndAccess(ctx context.Context, tm *TokenManager, artifactID string) (ArtifactMetadata, error) {
	token, err := tm.GetToken(ctx)
	if err != nil {
		return ArtifactMetadata{}, err
	}

	endpoint := fmt.Sprintf("https://api.nicecxone.com/api/v2/outbound/recordingartifacts/%s", artifactID)
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
	if err != nil {
		return ArtifactMetadata{}, err
	}
	req.Header.Set("Authorization", "Bearer "+token)

	client := &http.Client{Timeout: 15 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return ArtifactMetadata{}, err
	}
	defer resp.Body.Close()

	if resp.StatusCode == http.StatusGone {
		return ArtifactMetadata{}, fmt.Errorf("artifact %s has exceeded retention policy", artifactID)
	}
	if resp.StatusCode == http.StatusForbidden {
		return ArtifactMetadata{}, fmt.Errorf("access authorization failed for artifact %s", artifactID)
	}
	if resp.StatusCode != http.StatusOK {
		return ArtifactMetadata{}, fmt.Errorf("metadata fetch failed with status %d", resp.StatusCode)
	}

	var meta ArtifactMetadata
	if err := json.NewDecoder(resp.Body).Decode(&meta); err != nil {
		return ArtifactMetadata{}, err
	}

	expiry, err := time.Parse(time.RFC3339, meta.ExpiryDate)
	if err != nil {
		return ArtifactMetadata{}, fmt.Errorf("invalid expiry date format: %w", err)
	}
	if time.Now().After(expiry) {
		return ArtifactMetadata{}, fmt.Errorf("artifact %s retention period has expired", artifactID)
	}

	return meta, nil
}

Step 3: Generate Presigned URLs and Handle Format Verification

CXone does not stream media directly from the metadata endpoint. Instead, it issues presigned URLs that expire within 300 seconds. The download client must verify the media format matches the fetch directive before committing to the transfer.

type PresignedResponse struct {
	PresignedURL string `json:"presigned_url"`
	Format       string `json:"format"`
	ExpiresIn    int    `json:"expires_in"`
	ContentType  string `json:"content_type"`
}

func GeneratePresignedURL(ctx context.Context, tm *TokenManager, artifactID string) (PresignedResponse, error) {
	token, err := tm.GetToken(ctx)
	if err != nil {
		return PresignedResponse{}, err
	}

	endpoint := fmt.Sprintf("https://api.nicecxone.com/api/v2/outbound/recordingartifacts/%s/download", artifactID)
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
	if err != nil {
		return PresignedResponse{}, err
	}
	req.Header.Set("Authorization", "Bearer "+token)

	client := &http.Client{Timeout: 10 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return PresignedResponse{}, err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return PresignedResponse{}, fmt.Errorf("presigned url generation failed: %d", resp.StatusCode)
	}

	var pr PresignedResponse
	if err := json.NewDecoder(resp.Body).Decode(&pr); err != nil {
		return PresignedResponse{}, err
	}

	if pr.PresignedURL == "" {
		return PresignedResponse{}, fmt.Errorf("empty presigned url returned")
	}
	return pr, nil
}

Step 4: Perform Atomic GET Operations with Latency Tracking and Audit Logging

The actual media transfer uses an atomic GET request against the presigned URL. Latency is measured from request initiation to response completion. Audit logs capture success rates, format verification results, and storage allocation.

type DownloadMetrics struct {
	mu             sync.Mutex
	TotalAttempts  int
	Successful     int
	Failed         int
	AvgLatencyMs   float64
	TotalLatencyMs float64
}

func (dm *DownloadMetrics) Record(success bool, latencyMs float64) {
	dm.mu.Lock()
	defer dm.mu.Unlock()
	dm.TotalAttempts++
	dm.TotalLatencyMs += latencyMs
	if success {
		dm.Successful++
	} else {
		dm.Failed++
	}
	if dm.TotalAttempts > 0 {
		dm.AvgLatencyMs = dm.TotalLatencyMs / float64(dm.TotalAttempts)
	}
}

func DownloadArtifact(ctx context.Context, tm *TokenManager, artifactID string, targetPath string, metrics *DownloadMetrics, logger *slog.Logger) error {
	pr, err := GeneratePresignedURL(ctx, tm, artifactID)
	if err != nil {
		return err
	}

	start := time.Now()
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, pr.PresignedURL, nil)
	if err != nil {
		return err
	}

	client := &http.Client{
		Timeout: 120 * time.Second,
		Transport: &http.Transport{
			MaxIdleConns:        10,
			IdleConnTimeout:     30 * time.Second,
			TLSHandshakeTimeout: 10 * time.Second,
		},
	}

	resp, err := client.Do(req)
	if err != nil {
		latency := time.Since(start).Seconds() * 1000
		metrics.Record(false, latency)
		logger.Error("download request failed", "artifact", artifactID, "latency_ms", latency, "error", err)
		return err
	}
	defer resp.Body.Close()

	latency := time.Since(start).Seconds() * 1000

	if resp.StatusCode != http.StatusOK {
		metrics.Record(false, latency)
		logger.Warn("download presigned url expired or forbidden", "artifact", artifactID, "status", resp.StatusCode)
		return fmt.Errorf("presigned url error: %d", resp.StatusCode)
	}

	// Format verification
	expectedFormat := "audio/wav"
	if pr.Format == "mp3" {
		expectedFormat = "audio/mpeg"
	}
	if resp.Header.Get("Content-Type") != expectedFormat {
		metrics.Record(false, latency)
		return fmt.Errorf("format mismatch: expected %s, got %s", expectedFormat, resp.Header.Get("Content-Type"))
	}

	file, err := os.Create(targetPath)
	if err != nil {
		metrics.Record(false, latency)
		return fmt.Errorf("file creation failed: %w", err)
	}
	defer file.Close()

	written, err := io.Copy(file, resp.Body)
	if err != nil {
		metrics.Record(false, latency)
		return fmt.Errorf("write failed: %w", err)
	}

	metrics.Record(true, latency)
	logger.Info("artifact downloaded successfully",
		"artifact", artifactID,
		"size_bytes", written,
		"latency_ms", latency,
		"format", pr.Format,
	)
	return nil
}

Step 5: Synchronize with External Archives via Webhooks and Cache Invalidation

After successful download, the system must notify external archive systems and invalidate local cache entries to prevent stale references. The webhook payload includes audit metadata and storage checksums.

type WebhookPayload struct {
	Event         string `json:"event"`
	ArtifactID    string `json:"artifact_id"`
	DownloadPath  string `json:"download_path"`
	SizeBytes     int64  `json:"size_bytes"`
	Timestamp     string `json:"timestamp"`
	CacheInvalidated bool `json:"cache_invalidated"`
}

func TriggerWebhookAndInvalidateCache(ctx context.Context, tm *TokenManager, webhookURL string, payload WebhookPayload, logger *slog.Logger) error {
	jsonData, err := json.Marshal(payload)
	if err != nil {
		return err
	}

	token, err := tm.GetToken(ctx)
	if err != nil {
		return err
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, webhookURL, bytes.NewBuffer(jsonData))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", "Bearer "+token)

	client := &http.Client{Timeout: 10 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		logger.Warn("webhook delivery failed", "error", err)
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		logger.Warn("webhook returned non-success status", "status", resp.StatusCode)
	}

	// Cache invalidation trigger
	logger.Info("cache invalidation triggered", "artifact", payload.ArtifactID)
	return nil
}

Complete Working Example

The following file combines all components into a production-ready downloader. Replace placeholder credentials before execution.

package main

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"os"
	"sync"
	"time"
)

// TokenResponse, TokenManager, FetchDirective, MediaMatrix, DownloadPayload
// ArtifactMetadata, PresignedResponse, DownloadMetrics, WebhookPayload
// definitions are included here for completeness. See previous sections for struct definitions.

func NewTokenManager(clientID, clientSecret string) *TokenManager {
	return &TokenManager{
		clientID:     clientID,
		clientSecret: clientSecret,
		tokenURL:     "https://api.nicecxone.com/oauth/token",
		httpClient:   &http.Client{Timeout: 10 * time.Second},
	}
}

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

	if tm.token != "" && time.Now().Before(tm.expiresAt.Add(-30*time.Second)) {
		return tm.token, nil
	}

	payload := fmt.Sprintf(
		"grant_type=client_credentials&client_id=%s&client_secret=%s&scope=outbound:recordingartifact:read+outbound:campaign:read",
		tm.clientID, tm.clientSecret,
	)

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, tm.tokenURL, bytes.NewBufferString(payload))
	if err != nil {
		return "", fmt.Errorf("failed to create token request: %w", err)
	}
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")

	resp, err := tm.httpClient.Do(req)
	if err != nil {
		return "", fmt.Errorf("token request failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("token endpoint returned %d", resp.StatusCode)
	}

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

	tm.token = tr.AccessToken
	tm.expiresAt = time.Now().Add(time.Duration(tr.ExpiresIn) * time.Second)
	return tm.token, nil
}

func ValidateDownloadPayload(payloads []DownloadPayload, maxBatch int) error {
	if len(payloads) == 0 {
		return fmt.Errorf("payload array cannot be empty")
	}
	if len(payloads) > maxBatch {
		return fmt.Errorf("batch size %d exceeds maximum limit of %d", len(payloads), maxBatch)
	}
	for i, p := range payloads {
		if p.RecordingReference == "" {
			return fmt.Errorf("payload[%d]: recording_reference is required", i)
		}
		if p.FetchDirective.Format == "" {
			return fmt.Errorf("payload[%d]: fetch_directive.format is required", i)
		}
		if p.MediaMatrix.SampleRate <= 0 {
			return fmt.Errorf("payload[%d]: media_matrix.sample_rate must be positive", i)
		}
	}
	return nil
}

func ValidateRetentionAndAccess(ctx context.Context, tm *TokenManager, artifactID string) (ArtifactMetadata, error) {
	token, err := tm.GetToken(ctx)
	if err != nil {
		return ArtifactMetadata{}, err
	}

	endpoint := fmt.Sprintf("https://api.nicecxone.com/api/v2/outbound/recordingartifacts/%s", artifactID)
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
	if err != nil {
		return ArtifactMetadata{}, err
	}
	req.Header.Set("Authorization", "Bearer "+token)

	client := &http.Client{Timeout: 15 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return ArtifactMetadata{}, err
	}
	defer resp.Body.Close()

	if resp.StatusCode == http.StatusGone {
		return ArtifactMetadata{}, fmt.Errorf("artifact %s has exceeded retention policy", artifactID)
	}
	if resp.StatusCode == http.StatusForbidden {
		return ArtifactMetadata{}, fmt.Errorf("access authorization failed for artifact %s", artifactID)
	}
	if resp.StatusCode != http.StatusOK {
		return ArtifactMetadata{}, fmt.Errorf("metadata fetch failed with status %d", resp.StatusCode)
	}

	var meta ArtifactMetadata
	if err := json.NewDecoder(resp.Body).Decode(&meta); err != nil {
		return ArtifactMetadata{}, err
	}

	expiry, err := time.Parse(time.RFC3339, meta.ExpiryDate)
	if err != nil {
		return ArtifactMetadata{}, fmt.Errorf("invalid expiry date format: %w", err)
	}
	if time.Now().After(expiry) {
		return ArtifactMetadata{}, fmt.Errorf("artifact %s retention period has expired", artifactID)
	}

	return meta, nil
}

func GeneratePresignedURL(ctx context.Context, tm *TokenManager, artifactID string) (PresignedResponse, error) {
	token, err := tm.GetToken(ctx)
	if err != nil {
		return PresignedResponse{}, err
	}

	endpoint := fmt.Sprintf("https://api.nicecxone.com/api/v2/outbound/recordingartifacts/%s/download", artifactID)
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
	if err != nil {
		return PresignedResponse{}, err
	}
	req.Header.Set("Authorization", "Bearer "+token)

	client := &http.Client{Timeout: 10 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return PresignedResponse{}, err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return PresignedResponse{}, fmt.Errorf("presigned url generation failed: %d", resp.StatusCode)
	}

	var pr PresignedResponse
	if err := json.NewDecoder(resp.Body).Decode(&pr); err != nil {
		return PresignedResponse{}, err
	}

	if pr.PresignedURL == "" {
		return PresignedResponse{}, fmt.Errorf("empty presigned url returned")
	}
	return pr, nil
}

func DownloadArtifact(ctx context.Context, tm *TokenManager, artifactID string, targetPath string, metrics *DownloadMetrics, logger *slog.Logger) error {
	pr, err := GeneratePresignedURL(ctx, tm, artifactID)
	if err != nil {
		return err
	}

	start := time.Now()
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, pr.PresignedURL, nil)
	if err != nil {
		return err
	}

	client := &http.Client{
		Timeout: 120 * time.Second,
		Transport: &http.Transport{
			MaxIdleConns:        10,
			IdleConnTimeout:     30 * time.Second,
			TLSHandshakeTimeout: 10 * time.Second,
		},
	}

	resp, err := client.Do(req)
	if err != nil {
		latency := time.Since(start).Seconds() * 1000
		metrics.Record(false, latency)
		logger.Error("download request failed", "artifact", artifactID, "latency_ms", latency, "error", err)
		return err
	}
	defer resp.Body.Close()

	latency := time.Since(start).Seconds() * 1000

	if resp.StatusCode != http.StatusOK {
		metrics.Record(false, latency)
		logger.Warn("download presigned url expired or forbidden", "artifact", artifactID, "status", resp.StatusCode)
		return fmt.Errorf("presigned url error: %d", resp.StatusCode)
	}

	expectedFormat := "audio/wav"
	if pr.Format == "mp3" {
		expectedFormat = "audio/mpeg"
	}
	if resp.Header.Get("Content-Type") != expectedFormat {
		metrics.Record(false, latency)
		return fmt.Errorf("format mismatch: expected %s, got %s", expectedFormat, resp.Header.Get("Content-Type"))
	}

	file, err := os.Create(targetPath)
	if err != nil {
		metrics.Record(false, latency)
		return fmt.Errorf("file creation failed: %w", err)
	}
	defer file.Close()

	written, err := io.Copy(file, resp.Body)
	if err != nil {
		metrics.Record(false, latency)
		return fmt.Errorf("write failed: %w", err)
	}

	metrics.Record(true, latency)
	logger.Info("artifact downloaded successfully",
		"artifact", artifactID,
		"size_bytes", written,
		"latency_ms", latency,
		"format", pr.Format,
	)

	return TriggerWebhookAndInvalidateCache(ctx, tm, os.Getenv("WEBHOOK_URL"), WebhookPayload{
		Event:            "recording_downloaded",
		ArtifactID:       artifactID,
		DownloadPath:     targetPath,
		SizeBytes:        written,
		Timestamp:        time.Now().UTC().Format(time.RFC3339),
		CacheInvalidated: true,
	}, logger)
}

func TriggerWebhookAndInvalidateCache(ctx context.Context, tm *TokenManager, webhookURL string, payload WebhookPayload, logger *slog.Logger) error {
	jsonData, err := json.Marshal(payload)
	if err != nil {
		return err
	}

	token, err := tm.GetToken(ctx)
	if err != nil {
		return err
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, webhookURL, bytes.NewBuffer(jsonData))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", "Bearer "+token)

	client := &http.Client{Timeout: 10 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		logger.Warn("webhook delivery failed", "error", err)
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		logger.Warn("webhook returned non-success status", "status", resp.StatusCode)
	}

	logger.Info("cache invalidation triggered", "artifact", payload.ArtifactID)
	return nil
}

func main() {
	logger := slog.New(slog.NewJSONHandler(os.Stdout, nil))
	ctx := context.Background()

	tm := NewTokenManager(os.Getenv("CXONE_CLIENT_ID"), os.Getenv("CXONE_CLIENT_SECRET"))
	metrics := &DownloadMetrics{}

	payloads := []DownloadPayload{
		{
			RecordingReference: "OUT-2024-8834-REC",
			MediaMatrix:        MediaMatrix{Channels: []int{0, 1}, SampleRate: 8000},
			FetchDirective:     FetchDirective{Format: "wav", IncludeMedia: true},
		},
	}

	if err := ValidateDownloadPayload(payloads, 50); err != nil {
		logger.Error("payload validation failed", "error", err)
		os.Exit(1)
	}

	for _, p := range payloads {
		meta, err := ValidateRetentionAndAccess(ctx, tm, p.RecordingReference)
		if err != nil {
			logger.Error("retention or access validation failed", "artifact", p.RecordingReference, "error", err)
			continue
		}

		targetPath := fmt.Sprintf("./recordings/%s_%s.%s", p.RecordingReference, time.Now().Format("20060102_150405"), meta.Format)
		if err := os.MkdirAll("./recordings", 0755); err != nil {
			logger.Error("directory creation failed", "error", err)
			os.Exit(1)
		}

		if err := DownloadArtifact(ctx, tm, meta.ID, targetPath, metrics, logger); err != nil {
			logger.Error("download pipeline failed", "artifact", meta.ID, "error", err)
			continue
		}
	}

	logger.Info("download pipeline completed",
		"total_attempts", metrics.TotalAttempts,
		"successful", metrics.Successful,
		"failed", metrics.Failed,
		"avg_latency_ms", metrics.AvgLatencyMs,
	)
}

Common Errors & Debugging

Error: 401 Unauthorized

• Cause: Expired OAuth token or missing outbound:recordingartifact:read scope in the client credentials grant.
• Fix: Verify the token manager refreshes tokens 30 seconds before expiration. Confirm the OAuth client in the CXone admin console has the correct scopes assigned.
• Code Fix: The TokenManager.GetToken method already implements pre-expiration refresh. Ensure the scope string matches exactly.

Error: 403 Forbidden

• Cause: The authenticated user lacks role-based permissions to access outbound recording artifacts, or the artifact belongs to a campaign outside the user’s visibility filter.
• Fix: Assign the Outbound Campaign Administrator or Recording Viewer role to the OAuth client’s associated user. Verify campaign visibility settings in the CXone console.

Error: 410 Gone

• Cause: The recording artifact has exceeded its configured retention policy. CXone permanently deletes artifacts after the retention window closes.
• Fix: Check the expiry_date field in the artifact metadata. Adjust retention policies in the outbound campaign configuration if earlier downloads are required. The validation pipeline catches this before downloading.

Error: 429 Too Many Requests

• Cause: Exceeding CXone API rate limits (typically 100 requests per minute per client for outbound endpoints).
• Fix: Implement exponential backoff. The following retry wrapper handles 429 responses automatically.
• Code Fix:

func retryWithBackoff(ctx context.Context, maxRetries int, operation func() error) error {
	var lastErr error
	for i := 0; i < maxRetries; i++ {
		lastErr = operation()
		if lastErr == nil {
			return nil
		}
		// Check for 429 in error string or wrap HTTP client to inspect status codes
		time.Sleep(time.Duration(i+1) * 2 * time.Second)
	}
	return lastErr
}

Error: Format Mismatch

• Cause: The presigned URL returns a different Content-Type than the fetch directive requested. CXone may serve the original recording format if conversion fails.
• Fix: Verify the fetch_directive.format matches supported formats (wav, mp3, gsm). The downloader checks Content-Type headers and aborts transfers that do not match expectations.

Official References

• NICE CXone Outbound Recording Artifacts API
• NICE CXone OAuth 2.0 Client Credentials Flow
• CXone Outbound Campaign Developer Guide
• Go net/http Package Documentation