test otel

2025-11-05 10:23:00 +01:00
parent eb1f7750df
commit 82d564b136
6 changed files with 275 additions and 22 deletions
--- a/cmd/cart/main.go
+++ b/cmd/cart/main.go
@@ -1,6 +1,7 @@
 package main

 import (
+	"context"
 	"encoding/json"
 	"fmt"
 	"log"
@@ -206,9 +207,15 @@ func main() {
 	done := make(chan bool, 1)
 	signal.Notify(sigs, syscall.SIGTERM)

+	otelShutdown, err := setupOTelSDK(context.Background())
+	if err != nil {
+		log.Fatalf("Unable to start otel %v", err)
+	}
+
 	go func() {
 		sig := <-sigs
 		fmt.Println("Shutting down due to signal:", sig)
+		otelShutdown(context.Background())
 		diskStorage.Close()
 		pool.Close()

--- a/cmd/cart/otel.go
+++ b/cmd/cart/otel.go
@@ -0,0 +1,122 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"time"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/stdout/stdoutlog"
+	"go.opentelemetry.io/otel/exporters/stdout/stdoutmetric"
+	"go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
+	"go.opentelemetry.io/otel/log/global"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/sdk/log"
+	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/trace"
+)
+
+// setupOTelSDK bootstraps the OpenTelemetry pipeline.
+// If it does not return an error, make sure to call shutdown for proper cleanup.
+func setupOTelSDK(ctx context.Context) (func(context.Context) error, error) {
+	var shutdownFuncs []func(context.Context) error
+	var err error
+
+	// shutdown calls cleanup functions registered via shutdownFuncs.
+	// The errors from the calls are joined.
+	// Each registered cleanup will be invoked once.
+	shutdown := func(ctx context.Context) error {
+		var err error
+		for _, fn := range shutdownFuncs {
+			err = errors.Join(err, fn(ctx))
+		}
+		shutdownFuncs = nil
+		return err
+	}
+
+	// handleErr calls shutdown for cleanup and makes sure that all errors are returned.
+	handleErr := func(inErr error) {
+		err = errors.Join(inErr, shutdown(ctx))
+	}
+
+	// Set up propagator.
+	prop := newPropagator()
+	otel.SetTextMapPropagator(prop)
+
+	// Set up trace provider.
+	tracerProvider, err := newTracerProvider()
+	if err != nil {
+		handleErr(err)
+		return shutdown, err
+	}
+	shutdownFuncs = append(shutdownFuncs, tracerProvider.Shutdown)
+	otel.SetTracerProvider(tracerProvider)
+
+	// Set up meter provider.
+	meterProvider, err := newMeterProvider()
+	if err != nil {
+		handleErr(err)
+		return shutdown, err
+	}
+	shutdownFuncs = append(shutdownFuncs, meterProvider.Shutdown)
+	otel.SetMeterProvider(meterProvider)
+
+	// Set up logger provider.
+	loggerProvider, err := newLoggerProvider()
+	if err != nil {
+		handleErr(err)
+		return shutdown, err
+	}
+	shutdownFuncs = append(shutdownFuncs, loggerProvider.Shutdown)
+	global.SetLoggerProvider(loggerProvider)
+
+	return shutdown, err
+}
+
+func newPropagator() propagation.TextMapPropagator {
+	return propagation.NewCompositeTextMapPropagator(
+		propagation.TraceContext{},
+		propagation.Baggage{},
+	)
+}
+
+func newTracerProvider() (*trace.TracerProvider, error) {
+	traceExporter, err := stdouttrace.New(
+		stdouttrace.WithPrettyPrint())
+	if err != nil {
+		return nil, err
+	}
+
+	tracerProvider := trace.NewTracerProvider(
+		trace.WithBatcher(traceExporter,
+			// Default is 5s. Set to 1s for demonstrative purposes.
+			trace.WithBatchTimeout(time.Second)),
+	)
+	return tracerProvider, nil
+}
+
+func newMeterProvider() (*metric.MeterProvider, error) {
+	metricExporter, err := stdoutmetric.New()
+	if err != nil {
+		return nil, err
+	}
+
+	meterProvider := metric.NewMeterProvider(
+		metric.WithReader(metric.NewPeriodicReader(metricExporter,
+			// Default is 1m. Set to 3s for demonstrative purposes.
+			metric.WithInterval(3*time.Second))),
+	)
+	return meterProvider, nil
+}
+
+func newLoggerProvider() (*log.LoggerProvider, error) {
+	logExporter, err := stdoutlog.New()
+	if err != nil {
+		return nil, err
+	}
+
+	loggerProvider := log.NewLoggerProvider(
+		log.WithProcessor(log.NewBatchProcessor(logExporter)),
+	)
+	return loggerProvider, nil
+}
--- a/cmd/cart/pool-server.go
+++ b/cmd/cart/pool-server.go
@@ -17,6 +17,9 @@ import (
 	"github.com/gogo/protobuf/proto"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
+	"go.opentelemetry.io/contrib/bridges/otelslog"
+	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
+	"go.opentelemetry.io/otel"
 )

 var (
@@ -449,7 +452,10 @@ func CartIdHandler(fn func(cartId cart.CartId, w http.ResponseWriter, r *http.Re
 func (s *PoolServer) ProxyHandler(fn func(w http.ResponseWriter, r *http.Request, cartId cart.CartId) error) func(cartId cart.CartId, w http.ResponseWriter, r *http.Request) error {
 	return func(cartId cart.CartId, w http.ResponseWriter, r *http.Request) error {
 		if ownerHost, ok := s.OwnerHost(uint64(cartId)); ok {
+			ctx, span := tracer.Start(r.Context(), "proxy")
+			defer span.End()
 			handled, err := ownerHost.Proxy(uint64(cartId), w, r)
+			logger.InfoContext(ctx, fmt.Sprintf("owner host %s", ownerHost.Name()))
 			grainLookups.Inc()
 			if err == nil && handled {
 				return nil
@@ -461,6 +467,15 @@ func (s *PoolServer) ProxyHandler(fn func(w http.ResponseWriter, r *http.Request
 	}
 }

+var (
+	tracer = otel.Tracer(name)
+
+	// meter   = otel.Meter(name)
+	logger = otelslog.NewLogger(name)
+
+// rollCnt metric.Int64Counter
+)
+
 type AddVoucherRequest struct {
 	VoucherCode string `json:"code"`
 }
@@ -555,20 +570,26 @@ func (s *PoolServer) Serve() *http.ServeMux {
 		w.WriteHeader(http.StatusOK)
 	})

-	mux.HandleFunc("GET /", CookieCartIdHandler(s.ProxyHandler(s.GetCartHandler)))
-	mux.HandleFunc("GET /add/{sku}", CookieCartIdHandler(s.ProxyHandler(s.AddSkuToCartHandler)))
-	mux.HandleFunc("POST /add", CookieCartIdHandler(s.ProxyHandler(s.AddMultipleItemHandler)))
-	mux.HandleFunc("POST /", CookieCartIdHandler(s.ProxyHandler(s.AddSkuRequestHandler)))
-	mux.HandleFunc("POST /set", CookieCartIdHandler(s.ProxyHandler(s.SetCartItemsHandler)))
-	mux.HandleFunc("DELETE /{itemId}", CookieCartIdHandler(s.ProxyHandler(s.DeleteItemHandler)))
-	mux.HandleFunc("PUT /", CookieCartIdHandler(s.ProxyHandler(s.QuantityChangeHandler)))
-	mux.HandleFunc("DELETE /", CookieCartIdHandler(s.ProxyHandler(s.RemoveCartCookie)))
-	mux.HandleFunc("POST /delivery", CookieCartIdHandler(s.ProxyHandler(s.SetDeliveryHandler)))
-	mux.HandleFunc("DELETE /delivery/{deliveryId}", CookieCartIdHandler(s.ProxyHandler(s.RemoveDeliveryHandler)))
-	mux.HandleFunc("PUT /delivery/{deliveryId}/pickupPoint", CookieCartIdHandler(s.ProxyHandler(s.SetPickupPointHandler)))
-	mux.HandleFunc("PUT /voucher", CookieCartIdHandler(s.ProxyHandler(s.AddVoucherHandler)))
-	mux.HandleFunc("PUT /subscription-details", CookieCartIdHandler(s.ProxyHandler(s.SubscriptionDetailsHandler)))
-	mux.HandleFunc("DELETE /voucher/{voucherId}", CookieCartIdHandler(s.ProxyHandler(s.RemoveVoucherHandler)))
+	handleFunc := func(pattern string, handlerFunc func(http.ResponseWriter, *http.Request)) {
+		// Configure the "http.route" for the HTTP instrumentation.
+		handler := otelhttp.WithRouteTag(pattern, http.HandlerFunc(handlerFunc))
+		mux.Handle(pattern, handler)
+	}
+
+	handleFunc("GET /", CookieCartIdHandler(s.ProxyHandler(s.GetCartHandler)))
+	handleFunc("GET /add/{sku}", CookieCartIdHandler(s.ProxyHandler(s.AddSkuToCartHandler)))
+	handleFunc("POST /add", CookieCartIdHandler(s.ProxyHandler(s.AddMultipleItemHandler)))
+	handleFunc("POST /", CookieCartIdHandler(s.ProxyHandler(s.AddSkuRequestHandler)))
+	handleFunc("POST /set", CookieCartIdHandler(s.ProxyHandler(s.SetCartItemsHandler)))
+	handleFunc("DELETE /{itemId}", CookieCartIdHandler(s.ProxyHandler(s.DeleteItemHandler)))
+	handleFunc("PUT /", CookieCartIdHandler(s.ProxyHandler(s.QuantityChangeHandler)))
+	handleFunc("DELETE /", CookieCartIdHandler(s.ProxyHandler(s.RemoveCartCookie)))
+	handleFunc("POST /delivery", CookieCartIdHandler(s.ProxyHandler(s.SetDeliveryHandler)))
+	handleFunc("DELETE /delivery/{deliveryId}", CookieCartIdHandler(s.ProxyHandler(s.RemoveDeliveryHandler)))
+	handleFunc("PUT /delivery/{deliveryId}/pickupPoint", CookieCartIdHandler(s.ProxyHandler(s.SetPickupPointHandler)))
+	handleFunc("PUT /voucher", CookieCartIdHandler(s.ProxyHandler(s.AddVoucherHandler)))
+	handleFunc("PUT /subscription-details", CookieCartIdHandler(s.ProxyHandler(s.SubscriptionDetailsHandler)))
+	handleFunc("DELETE /voucher/{voucherId}", CookieCartIdHandler(s.ProxyHandler(s.RemoveVoucherHandler)))

 	//mux.HandleFunc("GET /checkout", CookieCartIdHandler(s.ProxyHandler(s.HandleCheckout)))
 	//mux.HandleFunc("GET /confirmation/{orderId}", CookieCartIdHandler(s.ProxyHandler(s.HandleConfirmation)))
--- a/go.mod
+++ b/go.mod
@@ -25,9 +25,11 @@ require (
 	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
 	github.com/dprotaso/go-yit v0.0.0-20220510233725-9ba8df137936 // indirect
 	github.com/emicklei/go-restful/v3 v3.13.0 // indirect
+	github.com/felixge/httpsnoop v1.0.4 // indirect
 	github.com/fxamacker/cbor/v2 v2.9.0 // indirect
 	github.com/getkin/kin-openapi v0.132.0 // indirect
 	github.com/go-logr/logr v1.4.3 // indirect
+	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/go-openapi/jsonpointer v0.22.1 // indirect
 	github.com/go-openapi/jsonreference v0.21.2 // indirect
 	github.com/go-openapi/swag v0.25.1 // indirect
@@ -66,6 +68,19 @@ require (
 	github.com/spf13/pflag v1.0.10 // indirect
 	github.com/vmware-labs/yaml-jsonpath v0.3.2 // indirect
 	github.com/x448/float16 v0.8.4 // indirect
+	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
+	go.opentelemetry.io/contrib/bridges/otelslog v0.13.0 // indirect
+	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.63.0 // indirect
+	go.opentelemetry.io/otel v1.38.0 // indirect
+	go.opentelemetry.io/otel/exporters/stdout/stdoutlog v0.14.0 // indirect
+	go.opentelemetry.io/otel/exporters/stdout/stdoutmetric v1.38.0 // indirect
+	go.opentelemetry.io/otel/exporters/stdout/stdouttrace v1.38.0 // indirect
+	go.opentelemetry.io/otel/log v0.14.0 // indirect
+	go.opentelemetry.io/otel/metric v1.38.0 // indirect
+	go.opentelemetry.io/otel/sdk v1.38.0 // indirect
+	go.opentelemetry.io/otel/sdk/log v0.14.0 // indirect
+	go.opentelemetry.io/otel/sdk/metric v1.38.0 // indirect
+	go.opentelemetry.io/otel/trace v1.38.0 // indirect
 	go.yaml.in/yaml/v2 v2.4.3 // indirect
 	go.yaml.in/yaml/v3 v3.0.4 // indirect
 	golang.org/x/mod v0.29.0 // indirect
--- a/go.sum
+++ b/go.sum
@@ -24,6 +24,8 @@ github.com/dprotaso/go-yit v0.0.0-20220510233725-9ba8df137936 h1:PRxIJD8XjimM5aT
 github.com/dprotaso/go-yit v0.0.0-20220510233725-9ba8df137936/go.mod h1:ttYvX5qlB+mlV1okblJqcSMtR4c52UKxDiX9GRBS8+Q=
 github.com/emicklei/go-restful/v3 v3.13.0 h1:C4Bl2xDndpU6nJ4bc1jXd+uTmYPVUwkD6bFY/oTyCes=
 github.com/emicklei/go-restful/v3 v3.13.0/go.mod h1:6n3XBCmQQb25CM2LCACGz8ukIrRry+4bhvbpWn3mrbc=
+github.com/felixge/httpsnoop v1.0.4 h1:NFTV2Zj1bL4mc9sqWACXbQFVBBg2W3GPvqp8/ESS2Wg=
+github.com/felixge/httpsnoop v1.0.4/go.mod h1:m8KPJKqk1gH5J9DgRY2ASl2lWCfGKXixSwevea8zH2U=
 github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
 github.com/fsnotify/fsnotify v1.4.9 h1:hsms1Qyu0jgnwNXIxa+/V/PDsU6CfLf6CNO8H7IWoS4=
 github.com/fsnotify/fsnotify v1.4.9/go.mod h1:znqG4EE+3YCdAaPaxE2ZRY/06pZUdp0tY4IgpuI1SZQ=
@@ -31,6 +33,7 @@ github.com/fxamacker/cbor/v2 v2.9.0 h1:NpKPmjDBgUfBms6tr6JZkTHtfFGcMKsw3eGcmD/sa
 github.com/fxamacker/cbor/v2 v2.9.0/go.mod h1:vM4b+DJCtHn+zz7h3FFp/hDAI9WNWCsZj23V5ytsSxQ=
 github.com/getkin/kin-openapi v0.132.0 h1:3ISeLMsQzcb5v26yeJrBcdTCEQTag36ZjaGk7MIRUwk=
 github.com/getkin/kin-openapi v0.132.0/go.mod h1:3OlG51PCYNsPByuiMB0t4fjnNlIDnaEDsjiKUV8nL58=
+github.com/go-logr/logr v1.2.2/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
 github.com/go-logr/logr v1.4.3 h1:CjnDlHq8ikf6E492q6eKboGOC0T8CDaOvkHCIg8idEI=
 github.com/go-logr/logr v1.4.3/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
 github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
@@ -204,12 +207,26 @@ github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9de
 github.com/yuin/goldmark v1.2.1/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 go.opentelemetry.io/auto/sdk v1.2.1 h1:jXsnJ4Lmnqd11kwkBV2LgLoFMZKizbCi5fNZ/ipaZ64=
 go.opentelemetry.io/auto/sdk v1.2.1/go.mod h1:KRTj+aOaElaLi+wW1kO/DZRXwkF4C5xPbEe3ZiIhN7Y=
+go.opentelemetry.io/contrib/bridges/otelslog v0.13.0 h1:bwnLpizECbPr1RrQ27waeY2SPIPeccCx/xLuoYADZ9s=
+go.opentelemetry.io/contrib/bridges/otelslog v0.13.0/go.mod h1:3nWlOiiqA9UtUnrcNk82mYasNxD8ehOspL0gOfEo6Y4=
+go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.63.0 h1:RbKq8BG0FI8OiXhBfcRtqqHcZcka+gU3cskNuf05R18=
+go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.63.0/go.mod h1:h06DGIukJOevXaj/xrNjhi/2098RZzcLTbc0jDAUbsg=
 go.opentelemetry.io/otel v1.38.0 h1:RkfdswUDRimDg0m2Az18RKOsnI8UDzppJAtj01/Ymk8=
 go.opentelemetry.io/otel v1.38.0/go.mod h1:zcmtmQ1+YmQM9wrNsTGV/q/uyusom3P8RxwExxkZhjM=
+go.opentelemetry.io/otel/exporters/stdout/stdoutlog v0.14.0 h1:B/g+qde6Mkzxbry5ZZag0l7QrQBCtVm7lVjaLgmpje8=
+go.opentelemetry.io/otel/exporters/stdout/stdoutlog v0.14.0/go.mod h1:mOJK8eMmgW6ocDJn6Bn11CcZ05gi3P8GylBXEkZtbgA=
+go.opentelemetry.io/otel/exporters/stdout/stdoutmetric v1.38.0 h1:wm/Q0GAAykXv83wzcKzGGqAnnfLFyFe7RslekZuv+VI=
+go.opentelemetry.io/otel/exporters/stdout/stdoutmetric v1.38.0/go.mod h1:ra3Pa40+oKjvYh+ZD3EdxFZZB0xdMfuileHAm4nNN7w=
+go.opentelemetry.io/otel/exporters/stdout/stdouttrace v1.38.0 h1:kJxSDN4SgWWTjG/hPp3O7LCGLcHXFlvS2/FFOrwL+SE=
+go.opentelemetry.io/otel/exporters/stdout/stdouttrace v1.38.0/go.mod h1:mgIOzS7iZeKJdeB8/NYHrJ48fdGc71Llo5bJ1J4DWUE=
+go.opentelemetry.io/otel/log v0.14.0 h1:2rzJ+pOAZ8qmZ3DDHg73NEKzSZkhkGIua9gXtxNGgrM=
+go.opentelemetry.io/otel/log v0.14.0/go.mod h1:5jRG92fEAgx0SU/vFPxmJvhIuDU9E1SUnEQrMlJpOno=
 go.opentelemetry.io/otel/metric v1.38.0 h1:Kl6lzIYGAh5M159u9NgiRkmoMKjvbsKtYRwgfrA6WpA=
 go.opentelemetry.io/otel/metric v1.38.0/go.mod h1:kB5n/QoRM8YwmUahxvI3bO34eVtQf2i4utNVLr9gEmI=
 go.opentelemetry.io/otel/sdk v1.38.0 h1:l48sr5YbNf2hpCUj/FoGhW9yDkl+Ma+LrVl8qaM5b+E=
 go.opentelemetry.io/otel/sdk v1.38.0/go.mod h1:ghmNdGlVemJI3+ZB5iDEuk4bWA3GkTpW+DOoZMYBVVg=
+go.opentelemetry.io/otel/sdk/log v0.14.0 h1:JU/U3O7N6fsAXj0+CXz21Czg532dW2V4gG1HE/e8Zrg=
+go.opentelemetry.io/otel/sdk/log v0.14.0/go.mod h1:imQvII+0ZylXfKU7/wtOND8Hn4OpT3YUoIgqJVksUkM=
 go.opentelemetry.io/otel/sdk/metric v1.38.0 h1:aSH66iL0aZqo//xXzQLYozmWrXxyFkBJ6qT5wthqPoM=
 go.opentelemetry.io/otel/sdk/metric v1.38.0/go.mod h1:dg9PBnW9XdQ1Hd6ZnRz689CbtrUp0wMMs9iPcgT9EZA=
 go.opentelemetry.io/otel/trace v1.38.0 h1:Fxk5bKrDZJUH+AMyyIXGcFAPah0oRcT+LuNtJrmcNLE=
--- a/pkg/inventory/redis_service.go
+++ b/pkg/inventory/redis_service.go
@@ -88,19 +88,49 @@ var (
 	ErrMissingReservation    = errors.New("missing reservation")
 )

+func makeKeysAndArgs(req ...ReserveRequest) ([]string, []string) {
+	keys := make([]string, len(req))
+	args := make([]string, len(req))
+	for i, r := range req {
+		if r.Quantity <= 0 {
+			return nil, nil
+		}
+		keys[i] = getInventoryKey(r.SKU, r.LocationID)
+		args[i] = strconv.Itoa(int(r.Quantity))
+	}
+	return keys, args
+}
+
+func (s *RedisInventoryService) ReservationCheck(req ...ReserveRequest) error {
+	if len(req) == 0 {
+		return ErrMissingReservation
+	}
+
+	keys, args := makeKeysAndArgs(req...)
+	if keys == nil || args == nil {
+		return ErrInvalidQuantity
+	}
+
+	cmd := reserveScript.Run(s.ctx, s.client, keys, args)
+	if err := cmd.Err(); err != nil {
+		return err
+	}
+	if val, err := cmd.Int(); err != nil {
+		return err
+	} else if val != 1 {
+		return ErrInsufficientInventory
+	}
+	return nil
+}
+
 func (s *RedisInventoryService) ReserveInventory(req ...ReserveRequest) error {
 	if len(req) == 0 {
 		return ErrMissingReservation
 	}

-	keys := make([]string, len(req))
-	args := make([]string, len(req))
-	for i, r := range req {
-		if r.Quantity <= 0 {
-			return ErrInvalidQuantity
-		}
-		keys[i] = getInventoryKey(r.SKU, r.LocationID)
-		args[i] = strconv.Itoa(int(r.Quantity))
+	keys, args := makeKeysAndArgs(req...)
+	if keys == nil || args == nil {
+		return ErrInvalidQuantity
 	}
 	cmd := reserveScript.Run(s.ctx, s.client, keys, args)
 	if err := cmd.Err(); err != nil {
@@ -114,6 +144,47 @@ func (s *RedisInventoryService) ReserveInventory(req ...ReserveRequest) error {
 	return nil
 }

+var reservationCheck = redis.NewScript(`
+-- Get the number of keys passed
+local num_keys = #KEYS
+
+-- Ensure the number of keys matches the number of quantities
+if num_keys ~= #ARGV then
+  return {err = "Script requires the same number of keys and quantities."}
+end
+
+local new_values = {}
+local payload = {}
+
+-- ---
+-- 1. CHECK PHASE
+-- ---
+-- Loop through all keys to check their values first
+for i = 1, num_keys do
+  local key = KEYS[i]
+  local quantity_to_check = tonumber(ARGV[i])
+
+  -- Fail if the quantity is not a valid number
+  if not quantity_to_check then
+    return {err = "Invalid quantity provided for key: " .. key}
+  end
+
+  -- Get the current value stored at the key
+  local current_val = tonumber(redis.call('GET', key))
+
+  -- Check the condition
+  -- Fail if:
+  -- 1. The key doesn't exist (current_val is nil)
+  -- 2. The value is not > the required quantity
+  if not current_val or current_val <= quantity_to_check then
+    -- Return 0 to indicate the operation failed and no changes were made
+    return 0
+  end
+end
+
+return 1
+`)
+
 var reserveScript = redis.NewScript(`
 -- Get the number of keys passed
 local num_keys = #KEYS