Complain if we detect sub-optimal ordering in distributed setup (#7576)

Fixes #6156

cmd/endpoint.go

@@ -30,6 +30,7 @@ import (
 	"time"
 
 	humanize "github.com/dustin/go-humanize"
+	"github.com/minio/cli"
 	"github.com/minio/minio-go/pkg/set"
 	"github.com/minio/minio/cmd/logger"
 	"github.com/minio/minio/pkg/cpu"
@@ -391,6 +392,26 @@ func NewEndpointList(args ...string) (endpoints EndpointList, err error) {
 	return endpoints, nil
 }
 
+func checkEndpointsSubOptimal(ctx *cli.Context, setupType SetupType, endpoints EndpointList) (err error) {
+	// Validate sub optimal ordering only for distributed setup.
+	if setupType != DistXLSetupType {
+		return nil
+	}
+	var endpointOrder int
+	err = fmt.Errorf("Too many disk args are local, input is in sub-optimal order. Please review input args: %s", ctx.Args())
+	for _, endpoint := range endpoints {
+		if endpoint.IsLocal {
+			endpointOrder++
+		} else {
+			endpointOrder--
+		}
+		if endpointOrder >= 2 {
+			return err
+		}
+	}
+	return nil
+}
+
 // Checks if there are any cross device mounts.
 func checkCrossDeviceMounts(endpoints EndpointList) (err error) {
 	var absPaths []string

cmd/endpoint_test.go

@@ -17,13 +17,53 @@
 package cmd
 
 import (
+	"flag"
 	"fmt"
 	"net/url"
 	"reflect"
 	"strings"
 	"testing"
+
+	"github.com/minio/cli"
 )
 
+func TestSubOptimalEndpointInput(t *testing.T) {
+	args1 := []string{"http://localhost/d1", "http://localhost/d2", "http://localhost/d3", "http://localhost/d4"}
+	args2 := []string{"http://example.org/d1", "http://example.com/d1", "http://example.net/d1", "http://example.edu/d1"}
+
+	tests := []struct {
+		setupType SetupType
+		ctx       *cli.Context
+		endpoints EndpointList
+		isErr     bool
+	}{
+		{
+			setupType: DistXLSetupType,
+			ctx:       cli.NewContext(cli.NewApp(), flag.NewFlagSet("", flag.ContinueOnError), nil),
+			endpoints: mustGetNewEndpointList(args1...),
+			isErr:     false,
+		},
+		{
+			setupType: DistXLSetupType,
+			ctx:       cli.NewContext(cli.NewApp(), flag.NewFlagSet("", flag.ContinueOnError), nil),
+			endpoints: mustGetNewEndpointList(args2...),
+			isErr:     false,
+		},
+	}
+	for i, test := range tests {
+		test := test
+		t.Run(fmt.Sprintf("Test%d", i+1), func(t *testing.T) {
+			err := checkEndpointsSubOptimal(test.ctx, test.setupType, test.endpoints)
+			if test.isErr && err == nil {
+				t.Error("expected err but found nil")
+			}
+			if !test.isErr && err != nil {
+				t.Errorf("expected err nil but found an err %s", err)
+			}
+		})
+	}
+}
+
 func TestNewEndpoint(t *testing.T) {
 	u1, _ := url.Parse("http://localhost/path")
 	u2, _ := url.Parse("https://example.org/path")

cmd/server-main.go

@@ -167,6 +167,8 @@ func serverHandleCmdArgs(ctx *cli.Context) {
 	}
 	logger.FatalIf(err, "Invalid command line arguments")
 
+	logger.LogIf(context.Background(), checkEndpointsSubOptimal(ctx, setupType, globalEndpoints))
+
 	globalMinioHost, globalMinioPort = mustSplitHostPort(globalMinioAddr)
 
 	// On macOS, if a process already listens on LOCALIPADDR:PORT, net.Listen() falls back