From ee028a4693eb09628e505ef9db6212e7b8c1b25b Mon Sep 17 00:00:00 2001
From: Harshavardhana <harsha@minio.io>
Date: Wed, 18 Aug 2021 18:05:05 -0700
Subject: [PATCH] listObjects optimized to handle max-keys=1 when prefix is
 object (#13000)

Some applications albeit poorly written rather than using headObject
rely on listObjects to check for existence of object, this unusual
request always has prefix=(to actual object) and max-keys=1

handle this situation specially such that we can avoid readdir()
on the top level parent to avoid sorting and skipping, ensuring
that such type of listObjects() always behaves similar to a
headObject() call.
---
 cmd/bootstrap-peer-server.go |  4 +++-
 cmd/erasure-server-pool.go   | 16 ++++++++++++++++
 cmd/metacache-walk.go        |  2 +-
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/cmd/bootstrap-peer-server.go b/cmd/bootstrap-peer-server.go
index b528139e2..5d0e1a538 100644
--- a/cmd/bootstrap-peer-server.go
+++ b/cmd/bootstrap-peer-server.go
@@ -188,7 +188,9 @@ func verifyServerSystemConfig(ctx context.Context, endpointServerPools EndpointS
 			// after 5 retries start logging that servers are not reachable yet
 			if retries >= 5 {
 				logger.Info(fmt.Sprintf("Waiting for atleast %d remote servers to be online for bootstrap check", len(clnts)/2))
-				logger.Info(fmt.Sprintf("Following servers are currently offline or unreachable %s", offlineEndpoints))
+				if len(offlineEndpoints) > 0 {
+					logger.Info(fmt.Sprintf("Following servers are currently offline or unreachable %s", offlineEndpoints))
+				}
 				retries = 0 // reset to log again after 5 retries.
 			}
 			offlineEndpoints = nil
diff --git a/cmd/erasure-server-pool.go b/cmd/erasure-server-pool.go
index 98a154e55..1c4cddad1 100644
--- a/cmd/erasure-server-pool.go
+++ b/cmd/erasure-server-pool.go
@@ -1060,6 +1060,22 @@ func maxKeysPlusOne(maxKeys int, addOne bool) int {
 
 func (z *erasureServerPools) ListObjects(ctx context.Context, bucket, prefix, marker, delimiter string, maxKeys int) (ListObjectsInfo, error) {
 	var loi ListObjectsInfo
+
+	if len(prefix) > 0 && maxKeys == 1 && delimiter == "" && marker == "" {
+		// Optimization for certain applications like
+		// - Cohesity
+		// - Actifio, Splunk etc.
+		// which send ListObjects requests where the actual object
+		// itself is the prefix and max-keys=1 in such scenarios
+		// we can simply verify locally if such an object exists
+		// to avoid the need for ListObjects().
+		objInfo, err := z.GetObjectInfo(ctx, bucket, prefix, ObjectOptions{NoLock: true})
+		if err == nil {
+			loi.Objects = append(loi.Objects, objInfo)
+			return loi, nil
+		}
+	}
+
 	opts := listPathOptions{
 		Bucket:      bucket,
 		Prefix:      prefix,
diff --git a/cmd/metacache-walk.go b/cmd/metacache-walk.go
index 2a0288a1e..e11d244fa 100644
--- a/cmd/metacache-walk.go
+++ b/cmd/metacache-walk.go
@@ -331,7 +331,7 @@ func (s *storageRESTServer) WalkDirHandler(w http.ResponseWriter, r *http.Reques
 	}
 
 	var reportNotFound bool
-	if v := vars[storageRESTReportNotFound]; v != "" {
+	if v := r.Form.Get(storageRESTReportNotFound); v != "" {
 		reportNotFound, err = strconv.ParseBool(v)
 		if err != nil {
 			s.writeErrorResponse(w, err)