Add rate limiter for S3 API layer (#9196)

- total number of S3 API calls per server
- maximum wait duration for any S3 API call

This implementation is primarily meant for situations
where HDDs are not capable enough to handle the incoming
workload and there is no way to throttle the client.

This feature allows MinIO server to throttle itself
such that we do not overwhelm the HDDs.

cmd/api-router.go

@@ -1,5 +1,5 @@
 /*
- * MinIO Cloud Storage, (C) 2016 MinIO, Inc.
+ * MinIO Cloud Storage, (C) 2016-2020 MinIO, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,9 +18,14 @@ package cmd
 
 import (
 	"net/http"
+	"strconv"
+	"time"
 
 	"github.com/gorilla/mux"
+	"github.com/minio/minio/cmd/config"
 	xhttp "github.com/minio/minio/cmd/http"
+	"github.com/minio/minio/cmd/logger"
+	"github.com/minio/minio/pkg/env"
 )
 
 func newHTTPServerFn() *xhttp.Server {
@@ -87,142 +92,229 @@ func registerAPIRouter(router *mux.Router, encryptionEnabled, allowSSEKMS bool)
 	}
 	routers = append(routers, apiRouter.PathPrefix("/{bucket}").Subrouter())
 
+	requestsMax, _ := strconv.Atoi(env.Get(config.EnvAPIRequestsMax, "0"))
+	if requestsMax < 0 {
+		requestsMax = 0 // 0 means unlimited
+	}
+
+	var (
+		enabled              bool
+		requestsMaxPerServer int
+		requestsDeadline     time.Duration
+	)
+
+	if len(globalEndpoints.Hosts()) == 0 {
+		requestsMaxPerServer = requestsMax
+	} else {
+		requestsMaxPerServer = requestsMax / len(globalEndpoints.Hosts())
+	}
+
+	enabled = requestsMaxPerServer > 0
+	if enabled {
+		var err error
+		requestsDeadline, err = time.ParseDuration(env.Get(config.EnvAPIRequestsDeadline, "10s"))
+		if err != nil {
+			logger.Info("(%s) parsing environment value MINIO_API_REQUESTS_DEADLINE, defaulting to 10 seconds", err)
+			requestsDeadline = 10 * time.Second
+		}
+	}
+
+	requestsMaxCh := make(chan struct{}, requestsMaxPerServer)
+
 	for _, bucket := range routers {
 		// Object operations
 		// HeadObject
-		bucket.Methods(http.MethodHead).Path("/{object:.+}").HandlerFunc(collectAPIStats("headobject", httpTraceAll(api.HeadObjectHandler)))
+		bucket.Methods(http.MethodHead).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("headobject", httpTraceAll(api.HeadObjectHandler)), enabled, requestsMaxCh, requestsDeadline))
 		// CopyObjectPart
-		bucket.Methods(http.MethodPut).Path("/{object:.+}").HeadersRegexp(xhttp.AmzCopySource, ".*?(\\/|%2F).*?").HandlerFunc(collectAPIStats("copyobjectpart", httpTraceAll(api.CopyObjectPartHandler))).Queries("partNumber", "{partNumber:[0-9]+}", "uploadId", "{uploadId:.*}")
+		bucket.Methods(http.MethodPut).Path("/{object:.+}").HeadersRegexp(xhttp.AmzCopySource, ".*?(\\/|%2F).*?").HandlerFunc(maxClients(collectAPIStats("copyobjectpart", httpTraceAll(api.CopyObjectPartHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("partNumber", "{partNumber:[0-9]+}", "uploadId", "{uploadId:.*}")
 		// PutObjectPart
-		bucket.Methods(http.MethodPut).Path("/{object:.+}").HandlerFunc(collectAPIStats("putobjectpart", httpTraceHdrs(api.PutObjectPartHandler))).Queries("partNumber", "{partNumber:[0-9]+}", "uploadId", "{uploadId:.*}")
+		bucket.Methods(http.MethodPut).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("putobjectpart", httpTraceHdrs(api.PutObjectPartHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("partNumber", "{partNumber:[0-9]+}", "uploadId", "{uploadId:.*}")
 		// ListObjectParts
-		bucket.Methods(http.MethodGet).Path("/{object:.+}").HandlerFunc(collectAPIStats("listobjectparts", httpTraceAll(api.ListObjectPartsHandler))).Queries("uploadId", "{uploadId:.*}")
+		bucket.Methods(http.MethodGet).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("listobjectparts", httpTraceAll(api.ListObjectPartsHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("uploadId", "{uploadId:.*}")
 		// CompleteMultipartUpload
-		bucket.Methods(http.MethodPost).Path("/{object:.+}").HandlerFunc(collectAPIStats("completemutipartupload", httpTraceAll(api.CompleteMultipartUploadHandler))).Queries("uploadId", "{uploadId:.*}")
+		bucket.Methods(http.MethodPost).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("completemutipartupload", httpTraceAll(api.CompleteMultipartUploadHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("uploadId", "{uploadId:.*}")
 		// NewMultipartUpload
-		bucket.Methods(http.MethodPost).Path("/{object:.+}").HandlerFunc(collectAPIStats("newmultipartupload", httpTraceAll(api.NewMultipartUploadHandler))).Queries("uploads", "")
+		bucket.Methods(http.MethodPost).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("newmultipartupload", httpTraceAll(api.NewMultipartUploadHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("uploads", "")
 		// AbortMultipartUpload
-		bucket.Methods(http.MethodDelete).Path("/{object:.+}").HandlerFunc(collectAPIStats("abortmultipartupload", httpTraceAll(api.AbortMultipartUploadHandler))).Queries("uploadId", "{uploadId:.*}")
+		bucket.Methods(http.MethodDelete).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("abortmultipartupload", httpTraceAll(api.AbortMultipartUploadHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("uploadId", "{uploadId:.*}")
 		// GetObjectACL - this is a dummy call.
-		bucket.Methods(http.MethodGet).Path("/{object:.+}").HandlerFunc(collectAPIStats("getobjectacl", httpTraceHdrs(api.GetObjectACLHandler))).Queries("acl", "")
+		bucket.Methods(http.MethodGet).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("getobjectacl", httpTraceHdrs(api.GetObjectACLHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("acl", "")
 		// PutObjectACL - this is a dummy call.
-		bucket.Methods(http.MethodPut).Path("/{object:.+}").HandlerFunc(collectAPIStats("putobjectacl", httpTraceHdrs(api.PutObjectACLHandler))).Queries("acl", "")
+		bucket.Methods(http.MethodPut).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("putobjectacl", httpTraceHdrs(api.PutObjectACLHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("acl", "")
 		// GetObjectTagging
-		bucket.Methods(http.MethodGet).Path("/{object:.+}").HandlerFunc(collectAPIStats("getobjecttagging", httpTraceHdrs(api.GetObjectTaggingHandler))).Queries("tagging", "")
+		bucket.Methods(http.MethodGet).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("getobjecttagging", httpTraceHdrs(api.GetObjectTaggingHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("tagging", "")
 		// PutObjectTagging
-		bucket.Methods(http.MethodPut).Path("/{object:.+}").HandlerFunc(collectAPIStats("putobjecttagging", httpTraceHdrs(api.PutObjectTaggingHandler))).Queries("tagging", "")
+		bucket.Methods(http.MethodPut).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("putobjecttagging", httpTraceHdrs(api.PutObjectTaggingHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("tagging", "")
 		// DeleteObjectTagging
-		bucket.Methods(http.MethodDelete).Path("/{object:.+}").HandlerFunc(collectAPIStats("deleteobjecttagging", httpTraceHdrs(api.DeleteObjectTaggingHandler))).Queries("tagging", "")
+		bucket.Methods(http.MethodDelete).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("deleteobjecttagging", httpTraceHdrs(api.DeleteObjectTaggingHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("tagging", "")
 		// SelectObjectContent
-		bucket.Methods(http.MethodPost).Path("/{object:.+}").HandlerFunc(collectAPIStats("selectobjectcontent", httpTraceHdrs(api.SelectObjectContentHandler))).Queries("select", "").Queries("select-type", "2")
+		bucket.Methods(http.MethodPost).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("selectobjectcontent", httpTraceHdrs(api.SelectObjectContentHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("select", "").Queries("select-type", "2")
 		// GetObjectRetention
-		bucket.Methods(http.MethodGet).Path("/{object:.+}").HandlerFunc(collectAPIStats("getobjectretention", httpTraceAll(api.GetObjectRetentionHandler))).Queries("retention", "")
+		bucket.Methods(http.MethodGet).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("getobjectretention", httpTraceAll(api.GetObjectRetentionHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("retention", "")
 		// GetObjectLegalHold
-		bucket.Methods(http.MethodGet).Path("/{object:.+}").HandlerFunc(collectAPIStats("getobjectlegalhold", httpTraceAll(api.GetObjectLegalHoldHandler))).Queries("legal-hold", "")
+		bucket.Methods(http.MethodGet).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("getobjectlegalhold", httpTraceAll(api.GetObjectLegalHoldHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("legal-hold", "")
 		// GetObject
-		bucket.Methods(http.MethodGet).Path("/{object:.+}").HandlerFunc(collectAPIStats("getobject", httpTraceHdrs(api.GetObjectHandler)))
+		bucket.Methods(http.MethodGet).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("getobject", httpTraceHdrs(api.GetObjectHandler)), enabled, requestsMaxCh, requestsDeadline))
 		// CopyObject
-		bucket.Methods(http.MethodPut).Path("/{object:.+}").HeadersRegexp(xhttp.AmzCopySource, ".*?(\\/|%2F).*?").HandlerFunc(collectAPIStats("copyobject", httpTraceAll(api.CopyObjectHandler)))
+		bucket.Methods(http.MethodPut).Path("/{object:.+}").HeadersRegexp(xhttp.AmzCopySource, ".*?(\\/|%2F).*?").HandlerFunc(maxClients(collectAPIStats("copyobject", httpTraceAll(api.CopyObjectHandler)), enabled, requestsMaxCh, requestsDeadline))
 		// PutObjectRetention
-		bucket.Methods(http.MethodPut).Path("/{object:.+}").HandlerFunc(collectAPIStats("putobjectretention", httpTraceAll(api.PutObjectRetentionHandler))).Queries("retention", "")
+		bucket.Methods(http.MethodPut).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("putobjectretention", httpTraceAll(api.PutObjectRetentionHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("retention", "")
 		// PutObjectLegalHold
-		bucket.Methods(http.MethodPut).Path("/{object:.+}").HandlerFunc(collectAPIStats("putobjectlegalhold", httpTraceAll(api.PutObjectLegalHoldHandler))).Queries("legal-hold", "")
+		bucket.Methods(http.MethodPut).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("putobjectlegalhold", httpTraceAll(api.PutObjectLegalHoldHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("legal-hold", "")
 
 		// PutObject
-		bucket.Methods(http.MethodPut).Path("/{object:.+}").HandlerFunc(collectAPIStats("putobject", httpTraceHdrs(api.PutObjectHandler)))
+		bucket.Methods(http.MethodPut).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("putobject", httpTraceHdrs(api.PutObjectHandler)), enabled, requestsMaxCh, requestsDeadline))
 		// DeleteObject
-		bucket.Methods(http.MethodDelete).Path("/{object:.+}").HandlerFunc(collectAPIStats("deleteobject", httpTraceAll(api.DeleteObjectHandler)))
+		bucket.Methods(http.MethodDelete).Path("/{object:.+}").HandlerFunc(
+			maxClients(collectAPIStats("deleteobject", httpTraceAll(api.DeleteObjectHandler)), enabled, requestsMaxCh, requestsDeadline))
 
 		/// Bucket operations
 		// GetBucketLocation
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("getbucketlocation", httpTraceAll(api.GetBucketLocationHandler))).Queries("location", "")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("getbucketlocation", httpTraceAll(api.GetBucketLocationHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("location", "")
 		// GetBucketPolicy
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("getbucketpolicy", httpTraceAll(api.GetBucketPolicyHandler))).Queries("policy", "")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("getbucketpolicy", httpTraceAll(api.GetBucketPolicyHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("policy", "")
 		// GetBucketLifecycle
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("getbucketlifecycle", httpTraceAll(api.GetBucketLifecycleHandler))).Queries("lifecycle", "")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("getbucketlifecycle", httpTraceAll(api.GetBucketLifecycleHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("lifecycle", "")
 		// GetBucketEncryption
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("getbucketencryption", httpTraceAll(api.GetBucketEncryptionHandler))).Queries("encryption", "")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("getbucketencryption", httpTraceAll(api.GetBucketEncryptionHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("encryption", "")
 
 		// Dummy Bucket Calls
 		// GetBucketACL -- this is a dummy call.
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("getbucketacl", httpTraceAll(api.GetBucketACLHandler))).Queries("acl", "")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("getbucketacl", httpTraceAll(api.GetBucketACLHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("acl", "")
 		// PutBucketACL -- this is a dummy call.
-		bucket.Methods(http.MethodPut).HandlerFunc(collectAPIStats("putbucketacl", httpTraceAll(api.PutBucketACLHandler))).Queries("acl", "")
+		bucket.Methods(http.MethodPut).HandlerFunc(
+			maxClients(collectAPIStats("putbucketacl", httpTraceAll(api.PutBucketACLHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("acl", "")
 		// GetBucketCors - this is a dummy call.
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("getbucketcors", httpTraceAll(api.GetBucketCorsHandler))).Queries("cors", "")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("getbucketcors", httpTraceAll(api.GetBucketCorsHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("cors", "")
 		// GetBucketWebsiteHandler - this is a dummy call.
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("getbucketwebsite", httpTraceAll(api.GetBucketWebsiteHandler))).Queries("website", "")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("getbucketwebsite", httpTraceAll(api.GetBucketWebsiteHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("website", "")
 		// GetBucketAccelerateHandler - this is a dummy call.
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("getbucketaccelerate", httpTraceAll(api.GetBucketAccelerateHandler))).Queries("accelerate", "")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("getbucketaccelerate", httpTraceAll(api.GetBucketAccelerateHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("accelerate", "")
 		// GetBucketRequestPaymentHandler - this is a dummy call.
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("getbucketrequestpayment", httpTraceAll(api.GetBucketRequestPaymentHandler))).Queries("requestPayment", "")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("getbucketrequestpayment", httpTraceAll(api.GetBucketRequestPaymentHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("requestPayment", "")
 		// GetBucketLoggingHandler - this is a dummy call.
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("getbucketlogging", httpTraceAll(api.GetBucketLoggingHandler))).Queries("logging", "")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("getbucketlogging", httpTraceAll(api.GetBucketLoggingHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("logging", "")
 		// GetBucketLifecycleHandler - this is a dummy call.
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("getbucketlifecycle", httpTraceAll(api.GetBucketLifecycleHandler))).Queries("lifecycle", "")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("getbucketlifecycle", httpTraceAll(api.GetBucketLifecycleHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("lifecycle", "")
 		// GetBucketReplicationHandler - this is a dummy call.
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("getbucketreplication", httpTraceAll(api.GetBucketReplicationHandler))).Queries("replication", "")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("getbucketreplication", httpTraceAll(api.GetBucketReplicationHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("replication", "")
 		// GetBucketTaggingHandler - this is a dummy call.
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("getbuckettagging", httpTraceAll(api.GetBucketTaggingHandler))).Queries("tagging", "")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("getbuckettagging", httpTraceAll(api.GetBucketTaggingHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("tagging", "")
 		//DeleteBucketWebsiteHandler
-		bucket.Methods(http.MethodDelete).HandlerFunc(collectAPIStats("deletebucketwebsite", httpTraceAll(api.DeleteBucketWebsiteHandler))).Queries("website", "")
+		bucket.Methods(http.MethodDelete).HandlerFunc(
+			maxClients(collectAPIStats("deletebucketwebsite", httpTraceAll(api.DeleteBucketWebsiteHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("website", "")
 		// DeleteBucketTaggingHandler
-		bucket.Methods(http.MethodDelete).HandlerFunc(collectAPIStats("deletebuckettagging", httpTraceAll(api.DeleteBucketTaggingHandler))).Queries("tagging", "")
+		bucket.Methods(http.MethodDelete).HandlerFunc(
+			maxClients(collectAPIStats("deletebuckettagging", httpTraceAll(api.DeleteBucketTaggingHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("tagging", "")
 
 		// GetBucketObjectLockConfig
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("getbucketobjectlockconfiguration", httpTraceAll(api.GetBucketObjectLockConfigHandler))).Queries("object-lock", "")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("getbucketobjectlockconfiguration", httpTraceAll(api.GetBucketObjectLockConfigHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("object-lock", "")
 		// GetBucketVersioning
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("getbucketversioning", httpTraceAll(api.GetBucketVersioningHandler))).Queries("versioning", "")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("getbucketversioning", httpTraceAll(api.GetBucketVersioningHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("versioning", "")
 		// GetBucketNotification
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("getbucketnotification", httpTraceAll(api.GetBucketNotificationHandler))).Queries("notification", "")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("getbucketnotification", httpTraceAll(api.GetBucketNotificationHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("notification", "")
 		// ListenBucketNotification
 		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("listenbucketnotification", httpTraceAll(api.ListenBucketNotificationHandler))).Queries("events", "{events:.*}")
 		// ListMultipartUploads
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("listmultipartuploads", httpTraceAll(api.ListMultipartUploadsHandler))).Queries("uploads", "")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("listmultipartuploads", httpTraceAll(api.ListMultipartUploadsHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("uploads", "")
 		// ListObjectsV2M
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("listobjectsv2M", httpTraceAll(api.ListObjectsV2MHandler))).Queries("list-type", "2", "metadata", "true")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("listobjectsv2M", httpTraceAll(api.ListObjectsV2MHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("list-type", "2", "metadata", "true")
 		// ListObjectsV2
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("listobjectsv2", httpTraceAll(api.ListObjectsV2Handler))).Queries("list-type", "2")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("listobjectsv2", httpTraceAll(api.ListObjectsV2Handler)), enabled, requestsMaxCh, requestsDeadline)).Queries("list-type", "2")
 		// ListBucketVersions
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("listbucketversions", httpTraceAll(api.ListBucketObjectVersionsHandler))).Queries("versions", "")
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("listbucketversions", httpTraceAll(api.ListBucketObjectVersionsHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("versions", "")
 		// ListObjectsV1 (Legacy)
-		bucket.Methods(http.MethodGet).HandlerFunc(collectAPIStats("listobjectsv1", httpTraceAll(api.ListObjectsV1Handler)))
+		bucket.Methods(http.MethodGet).HandlerFunc(
+			maxClients(collectAPIStats("listobjectsv1", httpTraceAll(api.ListObjectsV1Handler)), enabled, requestsMaxCh, requestsDeadline))
 		// PutBucketLifecycle
-		bucket.Methods(http.MethodPut).HandlerFunc(collectAPIStats("putbucketlifecycle", httpTraceAll(api.PutBucketLifecycleHandler))).Queries("lifecycle", "")
+		bucket.Methods(http.MethodPut).HandlerFunc(
+			maxClients(collectAPIStats("putbucketlifecycle", httpTraceAll(api.PutBucketLifecycleHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("lifecycle", "")
 		// PutBucketEncryption
-		bucket.Methods(http.MethodPut).HandlerFunc(collectAPIStats("putbucketencryption", httpTraceAll(api.PutBucketEncryptionHandler))).Queries("encryption", "")
+		bucket.Methods(http.MethodPut).HandlerFunc(
+			maxClients(collectAPIStats("putbucketencryption", httpTraceAll(api.PutBucketEncryptionHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("encryption", "")
 
 		// PutBucketPolicy
-		bucket.Methods(http.MethodPut).HandlerFunc(collectAPIStats("putbucketpolicy", httpTraceAll(api.PutBucketPolicyHandler))).Queries("policy", "")
+		bucket.Methods(http.MethodPut).HandlerFunc(
+			maxClients(collectAPIStats("putbucketpolicy", httpTraceAll(api.PutBucketPolicyHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("policy", "")
 
 		// PutBucketObjectLockConfig
-		bucket.Methods(http.MethodPut).HandlerFunc(collectAPIStats("putbucketobjectlockconfig", httpTraceAll(api.PutBucketObjectLockConfigHandler))).Queries("object-lock", "")
+		bucket.Methods(http.MethodPut).HandlerFunc(
+			maxClients(collectAPIStats("putbucketobjectlockconfig", httpTraceAll(api.PutBucketObjectLockConfigHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("object-lock", "")
 		// PutBucketVersioning
-		bucket.Methods(http.MethodPut).HandlerFunc(collectAPIStats("putbucketversioning", httpTraceAll(api.PutBucketVersioningHandler))).Queries("versioning", "")
+		bucket.Methods(http.MethodPut).HandlerFunc(
+			maxClients(collectAPIStats("putbucketversioning", httpTraceAll(api.PutBucketVersioningHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("versioning", "")
 		// PutBucketNotification
-		bucket.Methods(http.MethodPut).HandlerFunc(collectAPIStats("putbucketnotification", httpTraceAll(api.PutBucketNotificationHandler))).Queries("notification", "")
+		bucket.Methods(http.MethodPut).HandlerFunc(
+			maxClients(collectAPIStats("putbucketnotification", httpTraceAll(api.PutBucketNotificationHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("notification", "")
 		// PutBucket
-		bucket.Methods(http.MethodPut).HandlerFunc(collectAPIStats("putbucket", httpTraceAll(api.PutBucketHandler)))
+		bucket.Methods(http.MethodPut).HandlerFunc(
+			maxClients(collectAPIStats("putbucket", httpTraceAll(api.PutBucketHandler)), enabled, requestsMaxCh, requestsDeadline))
 		// HeadBucket
-		bucket.Methods(http.MethodHead).HandlerFunc(collectAPIStats("headbucket", httpTraceAll(api.HeadBucketHandler)))
+		bucket.Methods(http.MethodHead).HandlerFunc(
+			maxClients(collectAPIStats("headbucket", httpTraceAll(api.HeadBucketHandler)), enabled, requestsMaxCh, requestsDeadline))
 		// PostPolicy
-		bucket.Methods(http.MethodPost).HeadersRegexp(xhttp.ContentType, "multipart/form-data*").HandlerFunc(collectAPIStats("postpolicybucket", httpTraceHdrs(api.PostPolicyBucketHandler)))
+		bucket.Methods(http.MethodPost).HeadersRegexp(xhttp.ContentType, "multipart/form-data*").HandlerFunc(
+			maxClients(collectAPIStats("postpolicybucket", httpTraceHdrs(api.PostPolicyBucketHandler)), enabled, requestsMaxCh, requestsDeadline))
 		// DeleteMultipleObjects
-		bucket.Methods(http.MethodPost).HandlerFunc(collectAPIStats("deletemultipleobjects", httpTraceAll(api.DeleteMultipleObjectsHandler))).Queries("delete", "")
+		bucket.Methods(http.MethodPost).HandlerFunc(
+			maxClients(collectAPIStats("deletemultipleobjects", httpTraceAll(api.DeleteMultipleObjectsHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("delete", "")
 		// DeleteBucketPolicy
-		bucket.Methods(http.MethodDelete).HandlerFunc(collectAPIStats("deletebucketpolicy", httpTraceAll(api.DeleteBucketPolicyHandler))).Queries("policy", "")
+		bucket.Methods(http.MethodDelete).HandlerFunc(
+			maxClients(collectAPIStats("deletebucketpolicy", httpTraceAll(api.DeleteBucketPolicyHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("policy", "")
 		// DeleteBucketLifecycle
-		bucket.Methods(http.MethodDelete).HandlerFunc(collectAPIStats("deletebucketlifecycle", httpTraceAll(api.DeleteBucketLifecycleHandler))).Queries("lifecycle", "")
+		bucket.Methods(http.MethodDelete).HandlerFunc(
+			maxClients(collectAPIStats("deletebucketlifecycle", httpTraceAll(api.DeleteBucketLifecycleHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("lifecycle", "")
 		// DeleteBucketEncryption
-		bucket.Methods(http.MethodDelete).HandlerFunc(collectAPIStats("deletebucketencryption", httpTraceAll(api.DeleteBucketEncryptionHandler))).Queries("encryption", "")
+		bucket.Methods(http.MethodDelete).HandlerFunc(
+			maxClients(collectAPIStats("deletebucketencryption", httpTraceAll(api.DeleteBucketEncryptionHandler)), enabled, requestsMaxCh, requestsDeadline)).Queries("encryption", "")
 		// DeleteBucket
-		bucket.Methods(http.MethodDelete).HandlerFunc(collectAPIStats("deletebucket", httpTraceAll(api.DeleteBucketHandler)))
+		bucket.Methods(http.MethodDelete).HandlerFunc(
+			maxClients(collectAPIStats("deletebucket", httpTraceAll(api.DeleteBucketHandler)), enabled, requestsMaxCh, requestsDeadline))
 	}
 
 	/// Root operation
 
 	// ListBuckets
-	apiRouter.Methods(http.MethodGet).Path(SlashSeparator).HandlerFunc(collectAPIStats("listbuckets", httpTraceAll(api.ListBucketsHandler)))
+	apiRouter.Methods(http.MethodGet).Path(SlashSeparator).HandlerFunc(
+		maxClients(collectAPIStats("listbuckets", httpTraceAll(api.ListBucketsHandler)), enabled, requestsMaxCh, requestsDeadline))
 
 	// If none of the routes match add default error handler routes
 	apiRouter.NotFoundHandler = http.HandlerFunc(collectAPIStats("notfound", httpTraceAll(errorResponseHandler)))