RONDB-969: set MaxConcurrentReqs=GOMAXPROCS

Author: smkniazi

storage/ndb/rest-server/rest-api-server/README.md

@@ -195,7 +195,8 @@ Currently, the REST API server only supports [Hopsworks API Keys](https://docs.h
         "REST": {
                 "Enable": true,
                 "ServerIP": "localhost",
-                "ServerPort": 4406
+                "ServerPort": 4406,
+                "MaxConcurrentReqs": 0
         },
         "GRPC": {
                 "Enable": true,
@@ -295,14 +296,16 @@ Currently, the REST API server only supports [Hopsworks API Keys](https://docs.h
 
   - **OperationIDMaxSize:** Max length of operation ID. Default is 256 characters.
 
-- **REST** 
+- **REST**
 
-  - **Enable:** Enable/Disable REST Server Interface 
+  - **Enable:** Enable/Disable REST Server Interface
 
   - **ServerIP:** Binds the REST server to this IP. The default value is *localhost*
 
   - **ServerPort:** REST server port. The default port is *4406*
 
+  - **MaxConcurrentReqs:** Maximum number of concurrent requests the server will handle. The default value is *0* (auto mode). When set to *0*, the server automatically sets the limit to GOMAXPROCS (matching CPU resources). Set to a positive number to define a custom limit. This helps prevent overloading the server under high traffic.
+
 - **GRPC** 
 
   - **Enable:** Enable/Disable GRPC Server Interface 

storage/ndb/rest-server/rest-api-server/internal/config/init_defaults.go

@@ -65,7 +65,7 @@ func newWithDefaults() AllConfigs {
 			Enable:            true,
 			ServerIP:          "0.0.0.0",
 			ServerPort:        4406,
-			MaxConcurrentReqs: 0, // 0 = unlimited (default for backward compatibility)
+			MaxConcurrentReqs: 0, // 0 = auto (set to GOMAXPROCS), >0 = user-defined limit
 		},
 		RonDB: RonDB{
 			Mgmds: []Mgmd{

storage/ndb/rest-server/rest-api-server/internal/config/structs.go

@@ -77,7 +77,7 @@ type REST struct {
 	Enable              bool
 	ServerIP            string
 	ServerPort          uint16
-	MaxConcurrentReqs   uint32 // Maximum concurrent requests (0 = unlimited)
+	MaxConcurrentReqs   uint32 // Maximum concurrent requests (0 = auto/GOMAXPROCS, >0 = user-defined)
 }
 
 func (g *REST) Validate() error {

storage/ndb/rest-server/rest-api-server/internal/servers/rest/server.go

@@ -24,6 +24,7 @@ import (
 	"fmt"
 	"net/http"
 	"os"
+	"runtime"
 	"strings"
 	"syscall"
 	"time"
@@ -117,9 +118,22 @@ func registerHandlers(router *gin.Engine, heap *heap.Heap, apiKeyCache apikey.Ca
 	fvMeta *fsmeta.FeatureViewMetaDataCache, rdrsMetrics *metrics.RDRSMetrics) {
 	router.Use(ErrorHandler)
 
-	// Apply concurrency limiter if configured (0 = unlimited, no limiter)
+	// Apply concurrency limiter
+	// 0 = auto (set to GOMAXPROCS), >0 = user-defined limit
 	conf := config.GetAll()
-	if conf.REST.MaxConcurrentReqs > 0 {
+	if conf.REST.MaxConcurrentReqs == 0 {
+		// Auto mode: use GOMAXPROCS
+		var gomaxprocs int
+		if conf.Internal.GOMAXPROCS > 0 {
+			gomaxprocs = conf.Internal.GOMAXPROCS
+		} else {
+			gomaxprocs = runtime.GOMAXPROCS(0) // 0 means query current value without changing it
+		}
+		log.Infof("MaxConcurrentReqs set to auto mode: using GOMAXPROCS=%d", gomaxprocs)
+		router.Use(middleware.ConcurrencyLimiterWithQueue(uint32(gomaxprocs)))
+	} else {
+		// User-defined limit
+		log.Infof("MaxConcurrentReqs set to %d", conf.REST.MaxConcurrentReqs)
 		router.Use(middleware.ConcurrencyLimiterWithQueue(conf.REST.MaxConcurrentReqs))
 	}