Bump the minimum Kubernetes version to 1.14.x (#683)

This will be the lowest supported version of upstream Kubernetes, once 1.16 has cut.

version/version.go

@@ -18,6 +18,7 @@ package version
 
 import (
 	"fmt"
+	"os"
 
 	"github.com/rogpeppe/go-internal/semver"
 	"k8s.io/apimachinery/pkg/version"
@@ -31,7 +32,20 @@ type ServerVersioner interface {
 	ServerVersion() (*version.Info, error)
 }
 
-var minimumVersion = "v1.11.0"
+const (
+	// KubernetesMinVersionKey is the environment variable that can be used to override
+	// the Kubernetes minimum version required by Knative.
+	KubernetesMinVersionKey = "KUBERNETES_MIN_VERSION"
+
+	defaultMinimumVersion = "v1.14.0"
+)
+
+func getMinimumVersion() string {
+	if v := os.Getenv(KubernetesMinVersionKey); v != "" {
+		return v
+	}
+	return defaultMinimumVersion
+}
 
 // CheckMinimumVersion checks if the currently installed version of
 // Kubernetes is compatible with the minimum version required.
@@ -46,10 +60,13 @@ func CheckMinimumVersion(versioner ServerVersioner) error {
 	}
 	currentVersion := semver.Canonical(v.String())
 
+	minimumVersion := getMinimumVersion()
+
 	// Compare returns 1 if the first version is greater than the
 	// second version.
 	if semver.Compare(minimumVersion, currentVersion) == 1 {
-		return fmt.Errorf("kubernetes version %q is not compatible, need at least %q", currentVersion, minimumVersion)
+		return fmt.Errorf("kubernetes version %q is not compatible, need at least %q (this can be overriden with the env var %q)",
+			currentVersion, minimumVersion, KubernetesMinVersionKey)
 	}
 	return nil
 }

version/version_test.go

@@ -18,6 +18,7 @@ package version
 
 import (
 	"errors"
+	"os"
 	"testing"
 
 	"k8s.io/apimachinery/pkg/version"
@@ -34,36 +35,46 @@ func (t *testVersioner) ServerVersion() (*version.Info, error) {
 
 func TestVersionCheck(t *testing.T) {
 	tests := []struct {
-		name          string
-		actualVersion *testVersioner
-		wantError     bool
+		name            string
+		actualVersion   *testVersioner
+		versionOverride string
+		wantError       bool
 	}{{
 		name:          "greater version (patch)",
-		actualVersion: &testVersioner{version: "v1.11.1"},
+		actualVersion: &testVersioner{version: "v1.14.1"},
 	}, {
 		name:          "greater version (minor)",
-		actualVersion: &testVersioner{version: "v1.12.0"},
+		actualVersion: &testVersioner{version: "v1.15.0"},
 	}, {
 		name:          "same version",
-		actualVersion: &testVersioner{version: "v1.11.0"},
+		actualVersion: &testVersioner{version: "v1.14.0"},
 	}, {
 		name:          "smaller version",
-		actualVersion: &testVersioner{version: "v1.10.3"},
+		actualVersion: &testVersioner{version: "v1.13.3"},
 		wantError:     true,
 	}, {
 		name:          "error while fetching",
 		actualVersion: &testVersioner{err: errors.New("random error")},
 		wantError:     true,
+	}, {
+		name:            "smaller version",
+		versionOverride: "v1.13.0",
+		actualVersion:   &testVersioner{version: "v1.13.3"},
 	}}
 
 	for _, test := range tests {
-		err := CheckMinimumVersion(test.actualVersion)
-		if err == nil && test.wantError {
-			t.Errorf("Expected an error for minimum: %q, actual: %v", minimumVersion, test.actualVersion)
-		}
+		t.Run(test.name, func(t *testing.T) {
+			os.Setenv(KubernetesMinVersionKey, test.versionOverride)
+			defer os.Setenv(KubernetesMinVersionKey, "")
 
-		if err != nil && !test.wantError {
-			t.Errorf("Expected no error but got %v for minimum: %q, actual: %v", err, minimumVersion, test.actualVersion)
-		}
+			err := CheckMinimumVersion(test.actualVersion)
+			if err == nil && test.wantError {
+				t.Errorf("Expected an error for minimum: %q, actual: %v", getMinimumVersion(), test.actualVersion)
+			}
+
+			if err != nil && !test.wantError {
+				t.Errorf("Expected no error but got %v for minimum: %q, actual: %v", err, getMinimumVersion(), test.actualVersion)
+			}
+		})
 	}
 }