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-errors.go

@@ -211,6 +211,7 @@ const (
 	ErrInvalidResourceName
 	ErrServerNotInitialized
 	ErrOperationTimedOut
+	ErrOperationMaxedOut
 	ErrInvalidRequest
 	// MinIO storage class error codes
 	ErrInvalidStorageClass
@@ -1085,6 +1086,11 @@ var errorCodes = errorCodeMap{
 		Description:    "A timeout occurred while trying to lock a resource",
 		HTTPStatusCode: http.StatusRequestTimeout,
 	},
+	ErrOperationMaxedOut: {
+		Code:           "XMinioServerTimedOut",
+		Description:    "A timeout exceeded while waiting to proceed with the request",
+		HTTPStatusCode: http.StatusRequestTimeout,
+	},
 	ErrUnsupportedMetadata: {
 		Code:           "InvalidArgument",
 		Description:    "Your metadata headers are not supported.",

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)))

cmd/background-heal-ops.go

@@ -75,7 +75,7 @@ func (h *healRoutine) run(ctx context.Context, objAPI ObjectLayer) {
 			}
 
 			// Wait and proceed if there are active requests
-			waitForLowHTTPReq(int32(globalEndpoints.Nodes()))
+			waitForLowHTTPReq(int32(globalEndpoints.NEndpoints()))
 
 			var res madmin.HealResultItem
 			var err error

cmd/bootstrap-peer-server.go

@@ -62,9 +62,9 @@ func (s1 ServerSystemConfig) Diff(s2 ServerSystemConfig) error {
 		return fmt.Errorf("Expected platform '%s', found to be running '%s'",
 			s1.MinioPlatform, s2.MinioPlatform)
 	}
-	if s1.MinioEndpoints.Nodes() != s2.MinioEndpoints.Nodes() {
-		return fmt.Errorf("Expected number of endpoints %d, seen %d", s1.MinioEndpoints.Nodes(),
-			s2.MinioEndpoints.Nodes())
+	if s1.MinioEndpoints.NEndpoints() != s2.MinioEndpoints.NEndpoints() {
+		return fmt.Errorf("Expected number of endpoints %d, seen %d", s1.MinioEndpoints.NEndpoints(),
+			s2.MinioEndpoints.NEndpoints())
 	}
 
 	for i, ep := range s1.MinioEndpoints {
@@ -110,7 +110,7 @@ func registerBootstrapRESTHandlers(router *mux.Router) {
 		httpTraceHdrs(server.VerifyHandler))
 }
 
-// client to talk to bootstrap Nodes.
+// client to talk to bootstrap NEndpoints.
 type bootstrapRESTClient struct {
 	endpoint   Endpoint
 	restClient *rest.Client

cmd/config/constants.go

@@ -33,6 +33,10 @@ const (
 	EnvPublicIPs    = "MINIO_PUBLIC_IPS"
 	EnvEndpoints    = "MINIO_ENDPOINTS"
 
+	// API sub-system
+	EnvAPIRequestsMax      = "MINIO_API_REQUESTS_MAX"
+	EnvAPIRequestsDeadline = "MINIO_API_REQUESTS_DEADLINE"
+
 	EnvUpdate = "MINIO_UPDATE"
 
 	EnvWorm   = "MINIO_WORM"   // legacy

cmd/daily-lifecycle-ops.go

@@ -107,7 +107,7 @@ func lifecycleRound(ctx context.Context, objAPI ObjectLayer) error {
 				break
 			}
 
-			waitForLowHTTPReq(int32(globalEndpoints.Nodes()))
+			waitForLowHTTPReq(int32(globalEndpoints.NEndpoints()))
 
 			// Deletes a list of objects.
 			deleteErrs, err := objAPI.DeleteObjects(ctx, bucket.Name, objects)

cmd/endpoint.go

@@ -220,14 +220,28 @@ func (l EndpointZones) HTTPS() bool {
 	return l[0].Endpoints.HTTPS()
 }
 
-// Nodes - returns all nodes count
-func (l EndpointZones) Nodes() (count int) {
+// NEndpoints - returns all nodes count
+func (l EndpointZones) NEndpoints() (count int) {
 	for _, ep := range l {
 		count += len(ep.Endpoints)
 	}
 	return count
 }
 
+// Hosts - returns list of unique hosts
+func (l EndpointZones) Hosts() []string {
+	foundSet := set.NewStringSet()
+	for _, ep := range l {
+		for _, endpoint := range ep.Endpoints {
+			if foundSet.Contains(endpoint.Host) {
+				continue
+			}
+			foundSet.Add(endpoint.Host)
+		}
+	}
+	return foundSet.ToSlice()
+}
+
 // Endpoints - list of same type of endpoint.
 type Endpoints []Endpoint
 

cmd/handler-utils.go

@@ -28,6 +28,7 @@ import (
 	"net/url"
 	"regexp"
 	"strings"
+	"time"
 
 	xhttp "github.com/minio/minio/cmd/http"
 	"github.com/minio/minio/cmd/logger"
@@ -358,6 +359,31 @@ func httpTraceHdrs(f http.HandlerFunc) http.HandlerFunc {
 	}
 }
 
+// maxClients throttles the S3 API calls
+func maxClients(f http.HandlerFunc, enabled bool, requestsMaxCh chan struct{}, requestsDeadline time.Duration) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		if !enabled {
+			f.ServeHTTP(w, r)
+			return
+		}
+
+		select {
+		case requestsMaxCh <- struct{}{}:
+			defer func() { <-requestsMaxCh }()
+			f.ServeHTTP(w, r)
+		case <-time.NewTimer(requestsDeadline).C:
+
+			// Send a http timeout message
+			writeErrorResponse(r.Context(), w,
+				errorCodes.ToAPIErr(ErrOperationMaxedOut),
+				r.URL, guessIsBrowserReq(r))
+			return
+		case <-r.Context().Done():
+			return
+		}
+	}
+}
+
 func collectAPIStats(api string, f http.HandlerFunc) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 

cmd/iam-object-store.go

@@ -638,7 +638,7 @@ func listIAMConfigItems(objectAPI ObjectLayer, pathPrefix string, dirs bool,
 			if !globalSafeMode {
 				// Slow down listing and loading for config items to
 				// reduce load on the server
-				waitForLowHTTPReq(int32(globalEndpoints.Nodes()))
+				waitForLowHTTPReq(int32(globalEndpoints.NEndpoints()))
 			}
 
 			marker = lo.NextMarker

cmd/peer-rest-client.go

@@ -41,7 +41,7 @@ import (
 	trace "github.com/minio/minio/pkg/trace"
 )
 
-// client to talk to peer Nodes.
+// client to talk to peer NEndpoints.
 type peerRESTClient struct {
 	host       *xnet.Host
 	restClient *rest.Client

cmd/server-main.go

@@ -472,7 +472,7 @@ func serverMain(ctx *cli.Context) {
 func newObjectLayer(endpointZones EndpointZones) (newObject ObjectLayer, err error) {
 	// For FS only, directly use the disk.
 
-	if endpointZones.Nodes() == 1 {
+	if endpointZones.NEndpoints() == 1 {
 		// Initialize new FS object layer.
 		return NewFSObjectLayer(endpointZones[0].Endpoints[0].Path)
 	}

cmd/test-utils_test.go

@@ -1584,7 +1584,7 @@ func getRandomDisks(N int) ([]string, error) {
 // Initialize object layer with the supplied disks, objectLayer is nil upon any error.
 func newTestObjectLayer(endpointZones EndpointZones) (newObject ObjectLayer, err error) {
 	// For FS only, directly use the disk.
-	if endpointZones.Nodes() == 1 {
+	if endpointZones.NEndpoints() == 1 {
 		// Initialize new FS object layer.
 		return NewFSObjectLayer(endpointZones[0].Endpoints[0].Path)
 	}

docs/throttle/README.md

@@ -0,0 +1,35 @@
+# MinIO Server Throttling Guide [![Slack](https://slack.min.io/slack?type=svg)](https://slack.min.io) [![Docker Pulls](https://img.shields.io/docker/pulls/minio/minio.svg?maxAge=604800)](https://hub.docker.com/r/minio/minio/)
+
+MinIO server allows to throttle incoming requests:
+
+- limit the number of active requests allowed across the cluster
+- limit the wait duration for each request in the queue
+
+These values are enabled using environment variables *only*.
+
+## Configuring connection limit
+If you have traditional spinning (hdd) drives, some applications with high concurrency might require MinIO cluster to be tuned such that to avoid random I/O on the drives. The way to convert high concurrent I/O into a sequential I/O is by reducing the number of concurrent operations allowed per cluster. This allows MinIO cluster to be operationally resilient to such workloads, while also making sure the drives are at optimal efficiency and responsive.
+
+Example: Limit a MinIO cluster to accept at max 1600 simultaneous S3 API requests across 8 servers.
+```sh
+export MINIO_API_REQUESTS_MAX=1600
+export MINIO_ACCESS_KEY=your-access-key
+export MINIO_SECRET_KEY=your-secret-key
+minio server http://server{1...8}/mnt/hdd{1...16}
+```
+
+> NOTE: Setting MINIO_API_REQUESTS_MAX=0 means unlimited and that is the default behavior. These values need to be set based on your deployment requirements and application.
+
+## Configuring connection (wait) deadline
+This value works in conjunction with max connection setting, setting this value allows for long waiting requests to quickly time out when there is no slot available to perform the request.
+
+This will reduce the pileup of waiting requests when clients are not configured with timeouts. Default wait time is *10 seconds* if *MINIO_API_REQUESTS_MAX* is enabled. This may need to be tuned to your application needs.
+
+Example: Limit a MinIO cluster to accept at max 1600 simultaneous S3 API requests across 8 servers, and set the wait deadline of *2 minutes* per API operation.
+```sh
+export MINIO_API_REQUESTS_MAX=1600
+export MINIO_API_REQUESTS_DEADLINE=2m
+export MINIO_ACCESS_KEY=your-access-key
+export MINIO_SECRET_KEY=your-secret-key
+minio server http://server{1...8}/mnt/hdd{1...16}
+```