From 98a08e1644858d25cbc5c8613c02aebd3f558b8a Mon Sep 17 00:00:00 2001
From: Harshavardhana <harsha@minio.io>
Date: Thu, 1 Oct 2020 09:50:08 -0700
Subject: [PATCH] fix: protect updating latencies/throughput slices in obd
 (#10611)

Additionally close the transferChan upon function exit.
---
 cmd/peer-rest-client.go | 8 +++++++-
 pkg/disk/obd.go         | 7 +------
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/cmd/peer-rest-client.go b/cmd/peer-rest-client.go
index 3c098bb39..7b6f0dd85 100644
--- a/cmd/peer-rest-client.go
+++ b/cmd/peer-rest-client.go
@@ -134,6 +134,7 @@ func (r *nullReader) Read(b []byte) (int, error) {
 }
 
 func (client *peerRESTClient) doNetOBDTest(ctx context.Context, dataSize int64, threadCount uint) (info madmin.NetOBDInfo, err error) {
+	var mu sync.Mutex // mutex used to protect these slices in go-routines
 	latencies := []float64{}
 	throughputs := []float64{}
 
@@ -142,6 +143,8 @@ func (client *peerRESTClient) doNetOBDTest(ctx context.Context, dataSize int64,
 
 	totalTransferred := int64(0)
 	transferChan := make(chan int64, threadCount)
+	defer close(transferChan)
+
 	go func() {
 		for v := range transferChan {
 			atomic.AddInt64(&totalTransferred, v)
@@ -226,13 +229,16 @@ func (client *peerRESTClient) doNetOBDTest(ctx context.Context, dataSize int64,
 				/* Throughput = (total data transferred across all threads / time taken) */
 				throughput := float64((after - before)) / latency
 
+				// Protect updating latencies and throughputs slices from
+				// multiple go-routines.
+				mu.Lock()
 				latencies = append(latencies, latency)
 				throughputs = append(throughputs, throughput)
+				mu.Unlock()
 			}(i)
 		}
 	}
 	wg.Wait()
-	close(transferChan)
 
 	if err != nil {
 		return info, err
diff --git a/pkg/disk/obd.go b/pkg/disk/obd.go
index d439db1c6..c48511c00 100644
--- a/pkg/disk/obd.go
+++ b/pkg/disk/obd.go
@@ -27,9 +27,6 @@ import (
 	"github.com/montanaflynn/stats"
 )
 
-var globalLatency = map[string]Latency{}
-var globalThroughput = map[string]Throughput{}
-
 // Latency holds latency information for write operations to the drive
 type Latency struct {
 	Avg          float64 `json:"avg_secs,omitempty"`
@@ -154,6 +151,7 @@ func GetOBDInfo(ctx context.Context, drive, fsPath string) (Latency, Throughput,
 	if minThroughput, err = stats.Min(throughputs); err != nil {
 		return Latency{}, Throughput{}, err
 	}
+
 	t := Throughput{
 		Avg:          avgThroughput,
 		Percentile50: percentile50Throughput,
@@ -163,8 +161,5 @@ func GetOBDInfo(ctx context.Context, drive, fsPath string) (Latency, Throughput,
 		Max:          maxThroughput,
 	}
 
-	globalLatency[drive] = l
-	globalThroughput[drive] = t
-
 	return l, t, nil
 }