[process][ecs fargate] Fix CPU limit used (#8253)

* [process][ecs fargate] fix cpu limit calculation

pkg/process/checks/container_common.go

@@ -15,7 +15,8 @@ func calculateCtrPct(cur, prev, sys2, sys1 uint64, numCPU int, before time.Time)
 	}
 
 	// If we have system usage values then we need to calculate against those.
-	// XXX: Right now this only applies to ECS collection
+	// XXX: Right now this only applies to ECS collection. Note that the inclusion of CPUs is
+	// necessary because the value gets normalized against the CPU limit, which also accounts for CPUs.
 	if sys1 >= 0 && sys2 > 0 && sys2 != sys1 {
 		cpuDelta := float32(cur - prev)
 		sysDelta := float32(sys2 - sys1)

pkg/util/ecs/common.go

@@ -131,9 +131,9 @@ func convertMetaV2Container(c v2.Container, taskLimits map[string]float64) (*con
 		}
 	}
 
-	if l, found := c.Limits[cpuKey]; found && l > 0 {
-		container.Limits.CPULimit = formatContainerCPULimit(float64(l))
-	} else if l, found := taskLimits[cpuKey]; found && l > 0 {
+	// The task limit is required in Fargate (so this should always exist). Use this as the basis for the CPU limit
+	// because the container limits configured are treated as CPU shares, rather than a fixed limit to adhere to.
+	if l, found := taskLimits[cpuKey]; found && l > 0 {
 		container.Limits.CPULimit = formatTaskCPULimit(l)
 	} else {
 		container.Limits.CPULimit = 100
@@ -148,15 +148,8 @@ func convertMetaV2Container(c v2.Container, taskLimits map[string]float64) (*con
 	return container, dateError
 }
 
-func formatContainerCPULimit(val float64) float64 {
-	// The ECS API exposes the container CPU limit in CPU units
-	// Value is reported in Hz
-	return val / 1024 * 100
-}
-
 func formatTaskCPULimit(val float64) float64 {
 	// The ECS API exposes the task CPU limit with the format: 0.25, 0.5, 1, 2, 4
-	// Value is reported in Hz
 	return val * 100
 }
 

pkg/util/ecs/common_test.go

@@ -78,7 +78,7 @@ func TestConvertMetaV2Container(t *testing.T) {
 				StartedAt:   1517518511,
 				Type:        "ECS",
 				AddressList: []containers.NetworkAddress{},
-				Limits:      metrics.ContainerLimits{CPULimit: 50, MemLimit: 1024000000},
+				Limits:      metrics.ContainerLimits{CPULimit: 100, MemLimit: 1024000000},
 			},
 		},
 		{
@@ -158,7 +158,7 @@ func TestConvertMetaV2Container(t *testing.T) {
 				Name:        "ecs-nginx-5-nginx-curl-ccccb9f49db0dfe0d901",
 				Type:        "ECS",
 				AddressList: []containers.NetworkAddress{},
-				Limits:      metrics.ContainerLimits{CPULimit: 50, MemLimit: 1024000000},
+				Limits:      metrics.ContainerLimits{CPULimit: 100, MemLimit: 1024000000},
 			},
 		},
 	}

releasenotes/notes/fix-ecs-fargate-cpu-limit-93bd4656ee607c08.yaml

@@ -0,0 +1,11 @@
+# Each section from every release note are combined when the
+# CHANGELOG.rst is rendered. So the text needs to be worded so that
+# it does not depend on any information only available in another
+# section. This may mean repeating some details, but each section
+# must be readable independently of the other.
+#
+# Each section note must be formatted as reStructuredText.
+---
+fixes:
+  - |
+    Fix CPU limit used for Live Containers page in ECS Fargate environments.