From 62a1fdbbe460603a7cf0378ef8ac0c04c0040d74 Mon Sep 17 00:00:00 2001
From: oleksii_khanin <oleksii_khanin@epam.com>
Date: Mon, 14 Feb 2022 15:36:35 +0200
Subject: [PATCH 1/2] Fix metrics performance issue #15

Details see https://github.com/Mirantis/cri-dockerd/issues/15
---
 src/core/stats.go | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/src/core/stats.go b/src/core/stats.go
index 0d4ecb13e..4e8a9bc49 100644
--- a/src/core/stats.go
+++ b/src/core/stats.go
@@ -18,6 +18,7 @@ package core
 
 import (
 	"context"
+	"sync"
 
 	runtimeapi "k8s.io/cri-api/pkg/apis/runtime/v1alpha2"
 )
@@ -53,16 +54,21 @@ func (ds *dockerService) ListContainerStats(
 		return nil, err
 	}
 
-	var stats []*runtimeapi.ContainerStats
+	var mtx sync.Mutex
+	var wg sync.WaitGroup
+	var stats = make([]*runtimeapi.ContainerStats, 0, len(listResp.Containers))
 	for _, container := range listResp.Containers {
-		containerStats, err := ds.getContainerStats(container.Id)
-		if err != nil {
-			return nil, err
-		}
-		if containerStats != nil {
-			stats = append(stats, containerStats)
-		}
+		go func() {
+			wg.Add(1)
+			defer wg.Done()
+			if containerStats, err := ds.getContainerStats(container.Id); err == nil && containerStats != nil {
+				mtx.Lock()
+				stats = append(stats, containerStats)
+				mtx.Unlock()
+			}
+		}()
 	}
+	wg.Wait()
 
 	return &runtimeapi.ListContainerStatsResponse{Stats: stats}, nil
 }

From 10824fd2ff88548e8451ad07075ef4d0014f76b5 Mon Sep 17 00:00:00 2001
From: oleksii_khanin <oleksii_khanin@epam.com>
Date: Tue, 15 Feb 2022 16:06:10 +0200
Subject: [PATCH 2/2] Add error handling when get error from some container

---
 src/core/stats.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/core/stats.go b/src/core/stats.go
index 4e8a9bc49..7a5c3e957 100644
--- a/src/core/stats.go
+++ b/src/core/stats.go
@@ -18,6 +18,7 @@ package core
 
 import (
 	"context"
+	"github.com/sirupsen/logrus"
 	"sync"
 
 	runtimeapi "k8s.io/cri-api/pkg/apis/runtime/v1alpha2"
@@ -65,6 +66,8 @@ func (ds *dockerService) ListContainerStats(
 				mtx.Lock()
 				stats = append(stats, containerStats)
 				mtx.Unlock()
+			} else if err != nil {
+				logrus.Error(err, "Failed to get stats from container "+container.Id)
 			}
 		}()
 	}