From 3ff5f55dcbba1ae05893cee1ffe9e1500248d9c1 Mon Sep 17 00:00:00 2001
From: Klaus Post <klauspost@gmail.com>
Date: Mon, 8 Mar 2021 11:30:43 -0800
Subject: [PATCH] Fetch fileinfo concurrently (#11700)

For non-erasure setups fetch up to 10 fileinfos concurrently.

Fixes #11625
---
 cmd/object-api-common.go | 95 +++++++++++++++++++++++++---------------
 1 file changed, 60 insertions(+), 35 deletions(-)

diff --git a/cmd/object-api-common.go b/cmd/object-api-common.go
index bcb5ac5a1..041a17e30 100644
--- a/cmd/object-api-common.go
+++ b/cmd/object-api-common.go
@@ -19,12 +19,12 @@ package cmd
 import (
 	"context"
 	"errors"
-	"sync"
-
 	"strings"
+	"sync"
 
 	humanize "github.com/dustin/go-humanize"
 	"github.com/minio/minio/cmd/logger"
+	"github.com/minio/minio/pkg/sync/errgroup"
 )
 
 const (
@@ -340,58 +340,83 @@ func listObjects(ctx context.Context, obj ObjectLayer, bucket, prefix, marker, d
 		walkResultCh = startTreeWalk(ctx, bucket, prefix, marker, recursive, listDir, isLeaf, isLeafDir, endWalkCh)
 	}
 
-	var objInfos []ObjectInfo
 	var eof bool
 	var nextMarker string
 
 	// List until maxKeys requested.
-	for i := 0; i < maxKeys; {
+	g := errgroup.WithNErrs(maxKeys).WithConcurrency(10)
+	ctx, cancel := g.WithCancelOnError(ctx)
+	defer cancel()
+
+	objInfoFound := make([]*ObjectInfo, maxKeys)
+	var i int
+	for i = 0; i < maxKeys; i++ {
+		i := i
 		walkResult, ok := <-walkResultCh
 		if !ok {
 			// Closed channel.
 			eof = true
-			break
 		}
 
-		var objInfo ObjectInfo
-		var err error
 		if HasSuffix(walkResult.entry, SlashSeparator) {
-			for _, getObjectInfoDir := range getObjectInfoDirs {
-				objInfo, err = getObjectInfoDir(ctx, bucket, walkResult.entry)
-				if err == nil {
-					break
-				}
-				if err == errFileNotFound {
-					err = nil
-					objInfo = ObjectInfo{
-						Bucket: bucket,
-						Name:   walkResult.entry,
-						IsDir:  true,
+			g.Go(func() error {
+				for _, getObjectInfoDir := range getObjectInfoDirs {
+					objInfo, err := getObjectInfoDir(ctx, bucket, walkResult.entry)
+					if err == nil {
+						objInfoFound[i] = &objInfo
+						// Done...
+						return nil
 					}
+
+					// Add temp, may be overridden,
+					if err == errFileNotFound {
+						objInfoFound[i] = &ObjectInfo{
+							Bucket: bucket,
+							Name:   walkResult.entry,
+							IsDir:  true,
+						}
+						continue
+					}
+					return toObjectErr(err, bucket, prefix)
 				}
-			}
+				return nil
+			}, i)
 		} else {
-			objInfo, err = getObjInfo(ctx, bucket, walkResult.entry)
+			g.Go(func() error {
+				objInfo, err := getObjInfo(ctx, bucket, walkResult.entry)
+				if err != nil {
+					// Ignore errFileNotFound as the object might have got
+					// deleted in the interim period of listing and getObjectInfo(),
+					// ignore quorum error as it might be an entry from an outdated disk.
+					if IsErrIgnored(err, []error{
+						errFileNotFound,
+						errErasureReadQuorum,
+					}...) {
+						return nil
+					}
+					return toObjectErr(err, bucket, prefix)
+				}
+				objInfoFound[i] = &objInfo
+				return nil
+			}, i)
 		}
-		if err != nil {
-			// Ignore errFileNotFound as the object might have got
-			// deleted in the interim period of listing and getObjectInfo(),
-			// ignore quorum error as it might be an entry from an outdated disk.
-			if IsErrIgnored(err, []error{
-				errFileNotFound,
-				errErasureReadQuorum,
-			}...) {
-				continue
-			}
-			return loi, toObjectErr(err, bucket, prefix)
-		}
-		nextMarker = objInfo.Name
-		objInfos = append(objInfos, objInfo)
+
 		if walkResult.end {
 			eof = true
 			break
 		}
-		i++
+	}
+	if err := g.WaitErr(); err != nil {
+		return loi, err
+	}
+	// Copy found objects
+	objInfos := make([]ObjectInfo, 0, i+1)
+	for _, objInfo := range objInfoFound {
+		if objInfo == nil {
+			continue
+		}
+		objInfos = append(objInfos, *objInfo)
+		nextMarker = objInfo.Name
 	}
 
 	// Save list routine for the next marker if we haven't reached EOF.