Merge pull request #3658 from buildkite/ming/ps-1525

PS-1525: keep BUILDKITE_KUBERNETES_EXEC true for k8s bootstrap

Author: zhming0

clicommand/agent_start.go

@@ -747,10 +747,18 @@ var AgentStartCommand = cli.Command{
 		DebugHTTPFlag,
 		TraceHTTPFlag,
 
+		// Kubernetes
+		cli.BoolFlag{
+			Name: "kubernetes-exec",
+			Usage: "This is intended to be used only by the Buildkite k8s stack " +
+				"(github.com/buildkite/agent-stack-k8s); it enables a Unix socket for transporting " +
+				"logs and exit statuses between containers in a pod",
+			EnvVar: "BUILDKITE_KUBERNETES_EXEC",
+		},
+
 		// Other shared flags
 		RedactedVars,
 		StrictSingleHooksFlag,
-		KubernetesExecFlag,
 		TraceContextEncodingFlag,
 		NoMultipartArtifactUploadFlag,
 

clicommand/global.go

@@ -100,14 +100,6 @@ var (
 		EnvVar: "BUILDKITE_SOCKETS_PATH",
 	}
 
-	KubernetesExecFlag = cli.BoolFlag{
-		Name: "kubernetes-exec",
-		Usage: "This is intended to be used only by the Buildkite k8s stack " +
-			"(github.com/buildkite/agent-stack-k8s); it enables a Unix socket for transporting " +
-			"logs and exit statuses between containers in a pod",
-		EnvVar: "BUILDKITE_KUBERNETES_EXEC",
-	}
-
 	KubernetesContainerIDFlag = cli.IntFlag{
 		Name: "kubernetes-container-id",
 		Usage: "This is intended to be used only by the Buildkite k8s stack " +

clicommand/kubernetes_bootstrap.go

@@ -123,9 +123,11 @@ var KubernetesBootstrapCommand = cli.Command{
 			return err
 		}
 
-		// Ensure the Kubernetes socket setup is disabled in the subprocess
-		// (we're doing all that here).
-		environ.Set("BUILDKITE_KUBERNETES_EXEC", "false")
+		// BUILDKITE_KUBERNETES_EXEC is a legacy environment variable. It was used to activate the socket
+		// on the bootstrap command, and to activate the socket server on `buildkite-agent start`.
+		// The former has been superseded by this `kubernetes-bootstrap` command.
+		// We keep this env var because some users depend on it as a k8s environment detection mechanism.
+		environ.Set("BUILDKITE_KUBERNETES_EXEC", "true")
 
 		if _, exists := environ.Get("BUILDKITE_BUILD_CHECKOUT_PATH"); !exists {
 			// The OG agent runs as a long-live worker, therefore it set a checkout path dynamically to cater