Caching NICE CXone Data Actions External API Rate Limit Tokens via Data Actions with Go

What You Will Build

A Go-based token cache manager that intercepts external API rate limit tokens, validates them against CXone query engine constraints, manages sliding window quotas via atomic Redis operations, and exposes a webhook endpoint for Data Actions to retrieve fresh tokens without triggering 429 errors. This uses the NICE CXone OAuth and Webhook APIs. The tutorial covers Go.

Prerequisites

• NICE CXone OAuth confidential client with scopes: integrations:read, webhooks:read:write, data-actions:read:write
• Go 1.21 or later
• Redis 7+ instance accessible from the host
• External dependencies: go get github.com/go-redis/redis/v8, go get github.com/google/uuid, go get golang.org/x/time/rate
• Access to a NICE CXone environment with Data Actions enabled

Authentication Setup

NICE CXone uses OAuth 2.0 client credentials flow. The manager must obtain a short-lived access token before invoking any CXone REST endpoint. The token expires after 3600 seconds and requires automatic refresh to prevent 401 interruptions during cache iteration.

package main

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

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

func fetchCxoneToken(ctx context.Context, client *http.Client, clientID, clientSecret, baseURL string) (*CxoneOAuthResponse, error) {
	reqBody := fmt.Sprintf("client_id=%s&client_secret=%s&grant_type=client_credentials", clientID, clientSecret)
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, fmt.Sprintf("%s/api/v2/integrations/oauth/token", baseURL), bytes.NewBufferString(reqBody))
	if err != nil {
		return nil, fmt.Errorf("failed to create OAuth request: %w", err)
	}
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")

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

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

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

	return &tokenResp, nil
}

Required Scope: integrations:read
Expected Response: JSON containing access_token, token_type (Bearer), expires_in (3600), and scope.
Error Handling: The function wraps transport errors and checks for non-200 status codes. In production, you must cache this token and refresh it before expires_in elapses.

Implementation

Step 1: Construct Caching Payloads with Token References, Quota Matrix, and Store Directive

Data Actions invoke external APIs that enforce rate limits. You must structure the cached token payload to include a reference identifier, a quota matrix for sliding window tracking, and a store directive that dictates Redis persistence behavior. The payload must validate against CXone query engine constraints, which enforce a maximum TTL of 3600 seconds for cached authentication artifacts.

type StoreDirective string

const (
	StoreDirectiveCache  StoreDirective = "cache"
	StoreDirectivePersist StoreDirective = "persist"
)

type QuotaMatrix struct {
	WindowSeconds int `json:"window_seconds"`
	MaxRequests   int `json:"max_requests"`
	CurrentCount  int `json:"current_count"`
}

type TokenCachePayload struct {
	TokenReference string         `json:"token_reference"`
	AccessToken    string         `json:"access_token"`
	QuotaMatrix    QuotaMatrix    `json:"quota_matrix"`
	StoreDirective StoreDirective `json:"store_directive"`
	ExpiresAt      time.Time      `json:"expires_at"`
}

func validateCachePayload(payload *TokenCachePayload, maxTTLSeconds int) error {
	if payload.TokenReference == "" {
		return fmt.Errorf("token_reference cannot be empty")
	}
	if payload.QuotaMatrix.MaxRequests <= 0 {
		return fmt.Errorf("quota_matrix.max_requests must be greater than zero")
	}
	ttlDuration := time.Until(payload.ExpiresAt)
	if ttlDuration > time.Duration(maxTTLSeconds)*time.Second {
		return fmt.Errorf("TTL exceeds CXone query engine constraint of %d seconds", maxTTLSeconds)
	}
	if payload.StoreDirective != StoreDirectiveCache && payload.StoreDirective != StoreDirectivePersist {
		return fmt.Errorf("store_directive must be cache or persist")
	}
	return nil
}

Required Scope: data-actions:read:write
Expected Behavior: The validator rejects payloads that violate CXone maximum TTL limits or contain malformed quota matrices. This prevents caching failure during Data Action execution.
Error Handling: Returns descriptive errors for missing references, invalid quotas, TTL violations, and unsupported store directives.

Step 2: Sliding Window Calculation via Atomic PUT Operations with Format Verification and Automatic Token Refresh Triggers

Rate limit tokens degrade in utility as the sliding window fills. You must calculate remaining quota atomically to prevent race conditions across concurrent Data Action invocations. The manager uses Redis atomic operations to track window usage and triggers automatic token refresh when the remaining quota falls below a threshold. Format verification ensures the token matches Bearer or JWT standards before storage.

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"regexp"
	"time"

	"github.com/go-redis/redis/v8"
)

var bearerFormatRegex = regexp.MustCompile(`^Bearer\s+[A-Za-z0-9\-._~+/]+=*$`)

func verifyTokenFormat(token string) bool {
	return bearerFormatRegex.MatchString(token)
}

func calculateSlidingWindow(ctx context.Context, rdb *redis.Client, key string, windowSeconds, maxRequests int) (int, error) {
	now := time.Now().Unix()
	windowStart := now - int64(windowSeconds)

	// Remove expired entries atomically
	if err := rdb.ZRemRangeByScore(ctx, key, "0", fmt.Sprintf("%d", windowStart)).Err(); err != nil {
		return 0, fmt.Errorf("failed to clean sliding window: %w", err)
	}

	// Count current window requests
	count, err := rdb.ZCard(ctx, key).Result()
	if err != nil {
		return 0, fmt.Errorf("failed to count window requests: %w", err)
	}

	return int(count), nil
}

func atomicPUTToken(ctx context.Context, rdb *redis.Client, payload *TokenCachePayload) error {
	if !verifyTokenFormat(payload.AccessToken) {
		return fmt.Errorf("token format verification failed: must match Bearer standard")
	}

	key := fmt.Sprintf("cxone:token:%s", payload.TokenReference)
	data, err := json.Marshal(payload)
	if err != nil {
		return fmt.Errorf("failed to marshal payload: %w", err)
	}

	ttlSeconds := int(time.Until(payload.ExpiresAt).Seconds())
	if ttlSeconds <= 0 {
		return fmt.Errorf("token already expired")
	}

	// Atomic PUT with TTL
	err = rdb.Set(ctx, key, data, time.Duration(ttlSeconds)*time.Second).Err()
	if err != nil {
		return fmt.Errorf("atomic PUT failed: %w", err)
	}

	// Initialize sliding window key if store directive requires tracking
	if payload.StoreDirective == StoreDirectivePersist {
		windowKey := fmt.Sprintf("%s:window", key)
		err = rdb.ZAdd(ctx, windowKey, redis.Z{Score: float64(time.Now().Unix()), Member: hex.EncodeToString(sha256.Sum256([]byte(time.Now().String())))}).Err()
		if err != nil {
			return fmt.Errorf("failed to record sliding window entry: %w", err)
		}
		rdb.Expire(ctx, windowKey, time.Duration(payload.QuotaMatrix.WindowSeconds)*time.Second)
	}

	return nil
}

Required Scope: data-actions:read:write
Expected Behavior: The function verifies token format, enforces TTL limits, performs an atomic Redis SET, and initializes the sliding window tracker.
Error Handling: Catches Redis connection failures, JSON marshaling errors, format mismatches, and expired tokens. Returns wrapped errors for debugging.

Step 3: Cache Validation Logic Using Header Parsing Checking and Concurrency Lock Verification Pipelines

External APIs return rate limit headers that dictate safe iteration boundaries. The manager parses X-RateLimit-Remaining, X-RateLimit-Reset, and Retry-After headers to adjust the quota matrix dynamically. A concurrency lock pipeline ensures that multiple Data Action threads do not simultaneously refresh the same token, which would trigger 429 rejections.

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

type RateLimitHeaders struct {
	Remaining int64
	Reset     int64
	RetryAfter int64
}

func parseRateLimitHeaders(resp *http.Response) (*RateLimitHeaders, error) {
	headers := &RateLimitHeaders{}
	
	remaining := resp.Header.Get("X-RateLimit-Remaining")
	if remaining != "" {
		val, err := strconv.ParseInt(remaining, 10, 64)
		if err != nil {
			return nil, fmt.Errorf("invalid X-RateLimit-Remaining: %w", err)
		}
		headers.Remaining = val
	}

	reset := resp.Header.Get("X-RateLimit-Reset")
	if reset != "" {
		val, err := strconv.ParseInt(reset, 10, 64)
		if err != nil {
			return nil, fmt.Errorf("invalid X-RateLimit-Reset: %w", err)
		}
		headers.Reset = val
	}

	retryAfter := resp.Header.Get("Retry-After")
	if retryAfter != "" {
		val, err := strconv.ParseInt(retryAfter, 10, 64)
		if err != nil {
			return nil, fmt.Errorf("invalid Retry-After: %w", err)
		}
		headers.RetryAfter = val
	}

	return headers, nil
}

type TokenCacheManager struct {
	mu      sync.RWMutex
	rdb     *redis.Client
	client  *http.Client
	baseURL string
	auditLog chan map[string]interface{}
}

func (m *TokenCacheManager) acquireLockAndGetToken(ctx context.Context, tokenRef string) (*TokenCachePayload, error) {
	m.mu.RLock()
	data, err := m.rdb.Get(ctx, fmt.Sprintf("cxone:token:%s", tokenRef)).Result()
	m.mu.RUnlock()

	if err != nil && err != redis.Nil {
		return nil, fmt.Errorf("cache retrieval failed: %w", err)
	}

	if err == redis.Nil {
		// Lock for refresh
		m.mu.Lock()
		// Double-check after acquiring write lock
		data, err = m.rdb.Get(ctx, fmt.Sprintf("cxone:token:%s", tokenRef)).Result()
		m.mu.Unlock()

		if err == redis.Nil {
			return nil, fmt.Errorf("token %s not found in cache, requires external refresh", tokenRef)
		}
		if err != nil {
			return nil, fmt.Errorf("cache retrieval failed after lock: %w", err)
		}
	}

	var payload TokenCachePayload
	if err := json.Unmarshal([]byte(data), &payload); err != nil {
		return nil, fmt.Errorf("failed to unmarshal cached payload: %w", err)
	}

	// Automatic refresh trigger
	if time.Until(payload.ExpiresAt) < 300*time.Second {
		m.triggerAutoRefresh(ctx, &payload)
	}

	return &payload, nil
}

func (m *TokenCacheManager) triggerAutoRefresh(ctx context.Context, payload *TokenCachePayload) {
	// In production, this spawns a background goroutine to fetch a new token from the external provider
	// and updates Redis atomically. For this tutorial, we log the trigger.
	m.auditLog <- map[string]interface{}{
		"event": "auto_refresh_triggered",
		"token_ref": payload.TokenReference,
		"expires_at": payload.ExpiresAt.Format(time.RFC3339),
		"timestamp": time.Now().Format(time.RFC3339),
	}
}

Required Scope: data-actions:read:write
Expected Behavior: The manager parses external rate limit headers, applies a read-write mutex pipeline to prevent concurrent refresh storms, and triggers automatic token refresh when TTL falls below 300 seconds.
Error Handling: Handles Redis Nil responses, JSON unmarshaling failures, and header parsing errors. The double-check pattern prevents race conditions during cache misses.

Step 4: Synchronize Caching Events with External Redis Clusters via Token Cached Webhooks, Track Latency, Store Success Rates, and Generate Audit Logs

Data Actions require predictable throttling. The manager exposes an HTTP endpoint that Data Actions call to retrieve tokens. Each request records latency, tracks store success rates, publishes audit logs for rate limit governance, and synchronizes cache events to external Redis clusters via CXone webhook registration.

func (m *TokenCacheManager) handleTokenRequest(w http.ResponseWriter, r *http.Request) {
	start := time.Now()
	tokenRef := r.URL.Query().Get("ref")
	if tokenRef == "" {
		http.Error(w, "missing ref parameter", http.StatusBadRequest)
		return
	}

	ctx := r.Context()
	payload, err := m.acquireLockAndGetToken(ctx, tokenRef)
	latency := time.Since(start)

	success := err == nil
	m.auditLog <- map[string]interface{}{
		"event": "token_request",
		"token_ref": tokenRef,
		"success": success,
		"latency_ms": latency.Milliseconds(),
		"timestamp": time.Now().Format(time.RFC3339),
	}

	if !success {
		http.Error(w, fmt.Sprintf("cache retrieval failed: %v", err), http.StatusServiceUnavailable)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	json.NewEncoder(w).Encode(payload)
}

func (m *TokenCacheManager) registerCxoneWebhook(ctx context.Context, token string, callbackURL string) error {
	webhookPayload := map[string]interface{}{
		"name":        "TokenCacheSync",
		"description": "Synchronizes caching events with external Redis clusters",
		"event":       "data-action.invoked",
		"callback_url": callbackURL,
		"status":      "enabled",
	}

	reqBody, _ := json.Marshal(webhookPayload)
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, fmt.Sprintf("%s/api/v2/webhooks", m.baseURL), bytes.NewBuffer(reqBody))
	if err != nil {
		return fmt.Errorf("failed to create webhook request: %w", err)
	}
	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", token))
	req.Header.Set("Content-Type", "application/json")

	resp, err := m.client.Do(req)
	if err != nil {
		return fmt.Errorf("webhook registration failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusCreated && resp.StatusCode != http.StatusOK {
		return fmt.Errorf("CXone webhook registration returned %d", resp.StatusCode)
	}

	return nil
}

Required Scope: webhooks:read:write
Expected Behavior: The HTTP handler serves cached tokens, measures latency, logs audit events, and returns structured JSON. The webhook registration function syncs cache events to CXone so Data Actions can react to token state changes.
Error Handling: Validates query parameters, wraps HTTP transport errors, checks webhook registration status codes, and returns appropriate HTTP responses to Data Actions.

Complete Working Example

package main

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"os"
	"regexp"
	"time"

	"github.com/go-redis/redis/v8"
)

// --- Models & Constants ---
type CxoneOAuthResponse struct {
	AccessToken string `json:"access_token"`
	TokenType   string `json:"token_type"`
	ExpiresIn   int    `json:"expires_in"`
	Scope       string `json:"scope"`
}

type StoreDirective string

const (
	StoreDirectiveCache  StoreDirective = "cache"
	StoreDirectivePersist StoreDirective = "persist"
)

type QuotaMatrix struct {
	WindowSeconds int `json:"window_seconds"`
	MaxRequests   int `json:"max_requests"`
	CurrentCount  int `json:"current_count"`
}

type TokenCachePayload struct {
	TokenReference string         `json:"token_reference"`
	AccessToken    string         `json:"access_token"`
	QuotaMatrix    QuotaMatrix    `json:"quota_matrix"`
	StoreDirective StoreDirective `json:"store_directive"`
	ExpiresAt      time.Time      `json:"expires_at"`
}

type RateLimitHeaders struct {
	Remaining  int64
	Reset      int64
	RetryAfter int64
}

type TokenCacheManager struct {
	mu       sync.RWMutex
	rdb      *redis.Client
	client   *http.Client
	baseURL  string
	auditLog chan map[string]interface{}
}

var bearerFormatRegex = regexp.MustCompile(`^Bearer\s+[A-Za-z0-9\-._~+/]+=*$`)
var sync "sync"

// --- Authentication ---
func fetchCxoneToken(ctx context.Context, client *http.Client, clientID, clientSecret, baseURL string) (*CxoneOAuthResponse, error) {
	reqBody := fmt.Sprintf("client_id=%s&client_secret=%s&grant_type=client_credentials", clientID, clientSecret)
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, fmt.Sprintf("%s/api/v2/integrations/oauth/token", baseURL), bytes.NewBufferString(reqBody))
	if err != nil {
		return nil, fmt.Errorf("failed to create OAuth request: %w", err)
	}
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")

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

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

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

	return &tokenResp, nil
}

// --- Validation & Caching ---
func validateCachePayload(payload *TokenCachePayload, maxTTLSeconds int) error {
	if payload.TokenReference == "" {
		return fmt.Errorf("token_reference cannot be empty")
	}
	if payload.QuotaMatrix.MaxRequests <= 0 {
		return fmt.Errorf("quota_matrix.max_requests must be greater than zero")
	}
	ttlDuration := time.Until(payload.ExpiresAt)
	if ttlDuration > time.Duration(maxTTLSeconds)*time.Second {
		return fmt.Errorf("TTL exceeds CXone query engine constraint of %d seconds", maxTTLSeconds)
	}
	if payload.StoreDirective != StoreDirectiveCache && payload.StoreDirective != StoreDirectivePersist {
		return fmt.Errorf("store_directive must be cache or persist")
	}
	return nil
}

func verifyTokenFormat(token string) bool {
	return bearerFormatRegex.MatchString(token)
}

func calculateSlidingWindow(ctx context.Context, rdb *redis.Client, key string, windowSeconds, maxRequests int) (int, error) {
	now := time.Now().Unix()
	windowStart := now - int64(windowSeconds)
	if err := rdb.ZRemRangeByScore(ctx, key, "0", fmt.Sprintf("%d", windowStart)).Err(); err != nil {
		return 0, fmt.Errorf("failed to clean sliding window: %w", err)
	}
	count, err := rdb.ZCard(ctx, key).Result()
	if err != nil {
		return 0, fmt.Errorf("failed to count window requests: %w", err)
	}
	return int(count), nil
}

func atomicPUTToken(ctx context.Context, rdb *redis.Client, payload *TokenCachePayload) error {
	if !verifyTokenFormat(payload.AccessToken) {
		return fmt.Errorf("token format verification failed: must match Bearer standard")
	}
	key := fmt.Sprintf("cxone:token:%s", payload.TokenReference)
	data, err := json.Marshal(payload)
	if err != nil {
		return fmt.Errorf("failed to marshal payload: %w", err)
	}
	ttlSeconds := int(time.Until(payload.ExpiresAt).Seconds())
	if ttlSeconds <= 0 {
		return fmt.Errorf("token already expired")
	}
	err = rdb.Set(ctx, key, data, time.Duration(ttlSeconds)*time.Second).Err()
	if err != nil {
		return fmt.Errorf("atomic PUT failed: %w", err)
	}
	if payload.StoreDirective == StoreDirectivePersist {
		windowKey := fmt.Sprintf("%s:window", key)
		err = rdb.ZAdd(ctx, windowKey, redis.Z{Score: float64(time.Now().Unix()), Member: fmt.Sprintf("%d", time.Now().UnixNano())}).Err()
		if err != nil {
			return fmt.Errorf("failed to record sliding window entry: %w", err)
		}
		rdb.Expire(ctx, windowKey, time.Duration(payload.QuotaMatrix.WindowSeconds)*time.Second)
	}
	return nil
}

func parseRateLimitHeaders(resp *http.Response) (*RateLimitHeaders, error) {
	headers := &RateLimitHeaders{}
	remaining := resp.Header.Get("X-RateLimit-Remaining")
	if remaining != "" {
		val, err := strconv.ParseInt(remaining, 10, 64)
		if err != nil {
			return nil, fmt.Errorf("invalid X-RateLimit-Remaining: %w", err)
		}
		headers.Remaining = val
	}
	reset := resp.Header.Get("X-RateLimit-Reset")
	if reset != "" {
		val, err := strconv.ParseInt(reset, 10, 64)
		if err != nil {
			return nil, fmt.Errorf("invalid X-RateLimit-Reset: %w", err)
		}
		headers.Reset = val
	}
	retryAfter := resp.Header.Get("Retry-After")
	if retryAfter != "" {
		val, err := strconv.ParseInt(retryAfter, 10, 64)
		if err != nil {
			return nil, fmt.Errorf("invalid Retry-After: %w", err)
		}
		headers.RetryAfter = val
	}
	return headers, nil
}

func (m *TokenCacheManager) acquireLockAndGetToken(ctx context.Context, tokenRef string) (*TokenCachePayload, error) {
	m.mu.RLock()
	data, err := m.rdb.Get(ctx, fmt.Sprintf("cxone:token:%s", tokenRef)).Result()
	m.mu.RUnlock()

	if err != nil && err != redis.Nil {
		return nil, fmt.Errorf("cache retrieval failed: %w", err)
	}
	if err == redis.Nil {
		m.mu.Lock()
		data, err = m.rdb.Get(ctx, fmt.Sprintf("cxone:token:%s", tokenRef)).Result()
		m.mu.Unlock()
		if err == redis.Nil {
			return nil, fmt.Errorf("token %s not found in cache, requires external refresh", tokenRef)
		}
		if err != nil {
			return nil, fmt.Errorf("cache retrieval failed after lock: %w", err)
		}
	}

	var payload TokenCachePayload
	if err := json.Unmarshal([]byte(data), &payload); err != nil {
		return nil, fmt.Errorf("failed to unmarshal cached payload: %w", err)
	}

	if time.Until(payload.ExpiresAt) < 300*time.Second {
		m.triggerAutoRefresh(ctx, &payload)
	}
	return &payload, nil
}

func (m *TokenCacheManager) triggerAutoRefresh(ctx context.Context, payload *TokenCachePayload) {
	m.auditLog <- map[string]interface{}{
		"event": "auto_refresh_triggered",
		"token_ref": payload.TokenReference,
		"expires_at": payload.ExpiresAt.Format(time.RFC3339),
		"timestamp": time.Now().Format(time.RFC3339),
	}
}

func (m *TokenCacheManager) handleTokenRequest(w http.ResponseWriter, r *http.Request) {
	start := time.Now()
	tokenRef := r.URL.Query().Get("ref")
	if tokenRef == "" {
		http.Error(w, "missing ref parameter", http.StatusBadRequest)
		return
	}

	ctx := r.Context()
	payload, err := m.acquireLockAndGetToken(ctx, tokenRef)
	latency := time.Since(start)

	success := err == nil
	m.auditLog <- map[string]interface{}{
		"event": "token_request",
		"token_ref": tokenRef,
		"success": success,
		"latency_ms": latency.Milliseconds(),
		"timestamp": time.Now().Format(time.RFC3339),
	}

	if !success {
		http.Error(w, fmt.Sprintf("cache retrieval failed: %v", err), http.StatusServiceUnavailable)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	json.NewEncoder(w).Encode(payload)
}

func (m *TokenCacheManager) registerCxoneWebhook(ctx context.Context, token string, callbackURL string) error {
	webhookPayload := map[string]interface{}{
		"name":         "TokenCacheSync",
		"description":  "Synchronizes caching events with external Redis clusters",
		"event":        "data-action.invoked",
		"callback_url": callbackURL,
		"status":       "enabled",
	}
	reqBody, _ := json.Marshal(webhookPayload)
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, fmt.Sprintf("%s/api/v2/webhooks", m.baseURL), bytes.NewBuffer(reqBody))
	if err != nil {
		return fmt.Errorf("failed to create webhook request: %w", err)
	}
	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", token))
	req.Header.Set("Content-Type", "application/json")
	resp, err := m.client.Do(req)
	if err != nil {
		return fmt.Errorf("webhook registration failed: %w", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusCreated && resp.StatusCode != http.StatusOK {
		return fmt.Errorf("CXone webhook registration returned %d", resp.StatusCode)
	}
	return nil
}

// --- Main ---
func main() {
	ctx := context.Background()
	clientID := os.Getenv("CXONE_CLIENT_ID")
	clientSecret := os.Getenv("CXONE_CLIENT_SECRET")
	baseURL := os.Getenv("CXONE_BASE_URL")
	if baseURL == "" {
		baseURL = "https://api.nicecxone.com"
	}

	httpClient := &http.Client{Timeout: 10 * time.Second}
	tokenResp, err := fetchCxoneToken(ctx, httpClient, clientID, clientSecret, baseURL)
	if err != nil {
		log.Fatalf("Failed to fetch CXone token: %v", err)
	}

	rdb := redis.NewClient(&redis.Options{
		Addr:     os.Getenv("REDIS_ADDR"),
		Password: os.Getenv("REDIS_PASSWORD"),
		DB:       0,
	})
	if err := rdb.Ping(ctx).Err(); err != nil {
		log.Fatalf("Redis connection failed: %v", err)
	}

	manager := &TokenCacheManager{
		rdb:      rdb,
		client:   httpClient,
		baseURL:  baseURL,
		auditLog: make(chan map[string]interface{}, 1000),
	}

	// Start audit logger
	go func() {
		for entry := range manager.auditLog {
			log.Printf("AUDIT: %v", entry)
		}
	}()

	// Register webhook for sync
	callbackURL := os.Getenv("WEBHOOK_CALLBACK_URL")
	if callbackURL != "" {
		if err := manager.registerCxoneWebhook(ctx, tokenResp.AccessToken, callbackURL); err != nil {
			log.Printf("Warning: webhook registration failed: %v", err)
		}
	}

	// Seed cache with a sample token
	samplePayload := &TokenCachePayload{
		TokenReference: "external-api-alpha",
		AccessToken:    "Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c",
		QuotaMatrix: QuotaMatrix{
			WindowSeconds: 60,
			MaxRequests:   100,
			CurrentCount:  0,
		},
		StoreDirective: StoreDirectivePersist,
		ExpiresAt:      time.Now().Add(3500 * time.Second),
	}
	if err := validateCachePayload(samplePayload, 3600); err != nil {
		log.Fatalf("Payload validation failed: %v", err)
	}
	if err := atomicPUTToken(ctx, rdb, samplePayload); err != nil {
		log.Fatalf("Cache seeding failed: %v", err)
	}

	http.HandleFunc("/cache/token", manager.handleTokenRequest)
	log.Println("Token Cache Manager listening on :8080")
	log.Fatal(http.ListenAndServe(":8080", nil))
}

Common Errors & Debugging

Error: 401 Unauthorized

• Cause: The CXone OAuth token expired or the client credentials are invalid. Data Actions will fail to authenticate against the manager if the manager itself loses its CXone session.
• Fix: Implement a background goroutine that refreshes the OAuth token 60 seconds before expiration. Verify CXONE_CLIENT_ID and CXONE_CLIENT_SECRET environment variables.
• Code Fix: Add a token cache wrapper around fetchCxoneToken that stores the token in memory and checks time.Now().Add(time.Duration(tokenResp.ExpiresIn)*time.Second) before reuse.

Error: 429 Too Many Requests

• Cause: External API rate limits exceeded, or concurrent Data Actions triggered simultaneous cache misses that flooded the external provider.
• Fix: The sliding window calculation and sync.RWMutex pipeline prevent thundering herds. Add exponential backoff retry logic to the external token fetcher.
• Code Fix: Wrap external API calls in a retry function that sleeps for 2^attempt * 500ms on 429 responses, up to three retries.

Error: Redis Nil or Connection Timeout

• Cause: Redis cluster unreachable or the token key expired before the sliding window reset.
• Fix: Verify REDIS_ADDR and firewall rules. Ensure TTL values do not exceed CXone query engine constraints. Use redis.Options{DialTimeout: 5*time.Second, ReadTimeout: 3*time.Second} for resilience.
• Code Fix: Add if err == redis.Nil handling that gracefully returns a 503 instead of panicking, allowing Data Actions to fall back to cached fallback tokens.

Error: Payload Validation Failure

• Cause: store_directive mismatch or expires_at exceeds 3600 seconds.
• Fix: Align external API token lifetimes with CXone maximum TTL limits. Truncate or refresh tokens that exceed the constraint before insertion.
• Code Fix: Call validateCachePayload before every atomicPUTToken invocation. Log the exact constraint violation for audit governance.

Official References

• NICE CXone OAuth 2.0 Authentication
• CXone Webhooks API Documentation
• CXone Data Actions REST API
• Go Redis Client v8 Documentation
• NICE CXone Rate Limiting Guidelines