Detect the managed instance group that created a VM

detectors/gcp/gce.go

@@ -16,13 +16,19 @@ package gcp
 
 import (
 	"fmt"
+	"regexp"
 	"strings"
+
+	"cloud.google.com/go/compute/metadata"
 )
 
 // See the available GCE instance metadata:
-// https://cloud.google.com/compute/docs/metadata/default-metadata-values#vm_instance_metadata
+// https://cloud.google.com/compute/docs/metadata/predefined-metadata-keys#instance-metadata
 const machineTypeMetadataAttr = "instance/machine-type"
 
+// https://cloud.google.com/compute/docs/instance-groups/getting-info-about-migs#checking_if_a_vm_instance_is_part_of_a_mig
+const createdByMetadataAttr = "instance/created-by"
+
 func (d *Detector) onGCE() bool {
 	_, err := d.metadata.Get(machineTypeMetadataAttr)
 	return err == nil
@@ -73,3 +79,36 @@ func (d *Detector) GCEAvailabilityZoneAndRegion() (string, string, error) {
 	}
 	return zone, strings.Join(splitZone[0:2], "-"), nil
 }
+
+type ManagedInstanceGroup struct {
+	Name     string
+	Location string
+	Type     LocationType
+}
+
+var createdByMIGRE = regexp.MustCompile(`^projects/[^/]+/(zones|regions)/([^/]+)/instanceGroupManagers/([^/]+)$`)
+
+func (d *Detector) GCEManagedInstanceGroup() (ManagedInstanceGroup, error) {
+	createdBy, err := d.metadata.Get(createdByMetadataAttr)
+	if _, ok := err.(metadata.NotDefinedError); ok {
+		return ManagedInstanceGroup{}, nil
+	} else if err != nil {
+		return ManagedInstanceGroup{}, err
+	}
+	matches := createdByMIGRE.FindStringSubmatch(createdBy)
+	if matches == nil {
+		return ManagedInstanceGroup{}, nil
+	}
+
+	mig := ManagedInstanceGroup{
+		Name:     matches[3],
+		Location: matches[2],
+	}
+	switch matches[1] {
+	case "zones":
+		mig.Type = Zone
+	case "regions":
+		mig.Type = Region
+	}
+	return mig, nil
+}

detectors/gcp/gce_test.go

@@ -124,7 +124,7 @@ func TestGCEAvaiabilityZoneAndRegionNoZone(t *testing.T) {
 	assert.Equal(t, region, "")
 }
 
-func TestGCEAvaiabilityZoneAndRegionErr(t *testing.T) {
+func TestGCEAvailabilityZoneAndRegionErr(t *testing.T) {
 	d := NewTestDetector(&FakeMetadataProvider{
 		Err: fmt.Errorf("fake error"),
 	}, &FakeOSProvider{})
@@ -133,3 +133,58 @@ func TestGCEAvaiabilityZoneAndRegionErr(t *testing.T) {
 	assert.Equal(t, zone, "")
 	assert.Equal(t, region, "")
 }
+
+func TestGCEManagedInstanceGroup(t *testing.T) {
+	for _, test := range []struct {
+		createdBy string
+		mig       *ManagedInstanceGroup
+	}{
+		{
+			"projects/123456789012/zones/us-central1-f/instanceGroupManagers/igm-metadata",
+			&ManagedInstanceGroup{
+				Name:     "igm-metadata",
+				Location: "us-central1-f",
+				Type:     Zone,
+			},
+		},
+		{
+			"projects/123456789012/regions/us-central1-f/instanceGroupManagers/igm-metadata",
+			&ManagedInstanceGroup{
+				Name:     "igm-metadata",
+				Location: "us-central1-f",
+				Type:     Region,
+			},
+		},
+		{
+			"projects/123456789012/zones/us-central1-f/someOtherInstanceGroup/igm-metadata",
+			&ManagedInstanceGroup{},
+		},
+		{
+			"",
+			&ManagedInstanceGroup{},
+		},
+		{
+			"",
+			nil,
+		},
+	} {
+		t.Run(test.createdBy, func(t *testing.T) {
+			fmp := &FakeMetadataProvider{
+				Attributes: map[string]string{},
+			}
+			if test.createdBy != "" {
+				fmp.Attributes[createdByMetadataAttr] = test.createdBy
+			}
+			if test.mig == nil {
+				fmp.Err = fmt.Errorf("fake error")
+			}
+			d := NewTestDetector(fmp, &FakeOSProvider{})
+			mig, err := d.GCEManagedInstanceGroup()
+			if test.mig == nil {
+				assert.Error(t, err)
+			} else {
+				assert.Equal(t, mig, *test.mig)
+			}
+		})
+	}
+}