all: remove use old, overloaded of IN_KUBERNETES

Fixes golang/go#34956

Change-Id: Ie6f521eee5995102d6dc13f92ecca6601a68661b
Reviewed-on: https://go-review.googlesource.com/c/build/+/201739
Run-TryBot: Brad Fitzpatrick <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Bryan C. Mills <[email protected]>

Author: bradfitz

buildlet/kube.go

@@ -110,12 +110,7 @@ func StartPod(ctx context.Context, kubeClient *kubernetes.Client, podName, hostT
 							ContainerPort: 80,
 						},
 					},
-					Env: []api.EnvVar{
-						{
-							Name:  "IN_KUBERNETES",
-							Value: "1",
-						},
-					},
+					Env: []api.EnvVar{},
 				},
 			},
 		},

cmd/buildlet/buildlet.go

@@ -357,7 +357,7 @@ func listenForCoordinator() {
 // registerSignal if non-nil registers shutdown signals with the provided chan.
 var registerSignal func(chan<- os.Signal)
 
-var inKube, _ = strconv.ParseBool(os.Getenv("IN_KUBERNETES"))
+var inKube = os.Getenv("KUBERNETES_SERVICE_HOST") != ""
 
 // metadataValue returns the GCE metadata instance value for the given key.
 // If the metadata is not defined, the returned string is empty.

cmd/buildlet/stage0/stage0.go

@@ -302,13 +302,7 @@ func buildletURL() string {
 	}
 	switch osArch {
 	case "linux/amd64":
-		// Issue 25760: the s390x cross-compile builder is
-		// working under Kubernetes (which sets
-		// IN_KUBERNETES=1 in the env), but isn't working when
-		// run under Docker in COS (a Container-Optimized OS
-		// VM on GCE). Maybe something is hiding the GCE
-		// metadata service from the COS container now. As a
-		// test, just hard code the s390x builder:
+		// For the s390x cross-compile builder:
 		if os.Getenv("GOARCH") == "s390x" {
 			return "https://storage.googleapis.com/go-builder-data/buildlet.linux-amd64"
 		}
@@ -332,7 +326,7 @@ func buildletURL() string {
 	// The buildlet download URL is located in an env var
 	// when the buildlet is not running on GCE, or is running
 	// on Kubernetes.
-	if !metadata.OnGCE() || os.Getenv("IN_KUBERNETES") == "1" {
+	if !metadata.OnGCE() || os.Getenv("KUBERNETES_SERVICE_HOST") != "" {
 		if v := os.Getenv("META_BUILDLET_BINARY_URL"); v != "" {
 			return v
 		}

env/linux-arm/scaleway/Dockerfile

@@ -19,11 +19,6 @@ COPY stage0 /usr/local/bin/stage0
 
 ENV GO_BUILD_KEY_PATH /buildkey/gobuildkey
 ENV GO_BUILD_KEY_DELETE_AFTER_READ true
-
-# Not really, but we're in a container like Kubernetes, and this makes the syscall
-# package happy:
-ENV IN_KUBERNETES 1
-
 ENV GO_BUILDER_ENV host-linux-arm-scaleway
 
 # env specific

env/linux-arm64/Dockerfile

@@ -23,9 +23,3 @@ RUN curl -o  /usr/local/bin/stage0 https://storage.googleapis.com/go-builder-dat
 
 ENV GO_BUILD_KEY_DELETE_AFTER_READ true
 ENV GO_BUILD_KEY_PATH /buildkey/gobuildkey
-
-# Not really, but we're in a container like Kubernetes, and this makes the syscall
-# package happy:
-ENV IN_KUBERNETES 1
-
-