Add minimum image age option

gc/collector.go

@@ -27,10 +27,11 @@ type Collector interface {
 type collector struct {
 	client docker.APIClient
 
-	whitelist []string // reserved containers
-	reserved  []string // reserved images
-	threshold int64    // target threshold in bytes
-	filter    FilterFunc
+	whitelist 	[]string // reserved containers
+	reserved  	[]string // reserved images
+	threshold 	int64    // target threshold in bytes
+	minImageAge	time.Duration
+	filter    	FilterFunc
 }
 
 // New returns a garbage collector.

gc/image.go

@@ -72,7 +72,7 @@ func (c *collector) collectImages(ctx context.Context) error {
 		if isImageUsed(image, df.Containers) {
 			continue
 		}
-		if time.Unix(image.Created, 0).Add(time.Hour).After(now) {
+		if time.Unix(image.Created, 0).Add(c.minImageAge).After(now) {
 			continue
 		}
 

gc/image_test.go

@@ -129,6 +129,47 @@ func TestCollectImages_BelowThreshold(t *testing.T) {
 	}
 }
 
+// this test verifies that we do not purge images that are not old enough
+func TestCollectImages_SkipNotOldEnough(t *testing.T) {
+	controller := gomock.NewController(t)
+	defer controller.Finish()
+
+	mockdf := types.DiskUsage{
+		LayersSize: 1,
+		Images: []*types.ImageSummary{
+			// this image was created 20 mins ago
+			{
+				ID:      "a180b24e38ed",
+				Created: time.Now().Add(-20*time.Minute).Unix(),
+			},
+			// this image was created 40 mins ago
+			{
+				ID:      "481995377a04",
+				Created: time.Now().Add(-40*time.Minute).Unix(),
+			},
+		},
+	}
+
+	mockImages := []types.ImageInspect{
+		{ID: "a180b24e38ed"},
+		{ID: "481995377a04"},
+	}
+
+	client := mocks.NewMockAPIClient(controller)
+	client.EXPECT().DiskUsage(gomock.Any()).Return(mockdf, nil)
+
+	// We DO NOT expect image 0 to be removed since is not old enough
+	client.EXPECT().ImageInspectWithRaw(gomock.Any(), mockImages[1].ID).Return(mockImages[1], nil, nil)
+	client.EXPECT().ImageRemove(gomock.Any(), mockImages[1].ID, imageRemoveOpts).Return(nil, nil)
+
+	// Minimum image age set to 30 mins
+	c := New(client, WithMinImageAge(time.Hour/2)).(*collector)
+	err := c.collectImages(context.Background())
+	if err != nil {
+		t.Error(err)
+	}
+}
+
 // this test verifies that we do not purge images that are
 // in-use by the system or are newly created.
 func TestCollectImages_Skip(t *testing.T) {
@@ -156,7 +197,7 @@ func TestCollectImages_Skip(t *testing.T) {
 	client := mocks.NewMockAPIClient(controller)
 	client.EXPECT().DiskUsage(gomock.Any()).Return(mockdf, nil)
 
-	c := New(client).(*collector)
+	c := New(client, WithMinImageAge(time.Hour)).(*collector)
 	err := c.collectImages(context.Background())
 	if err != nil {
 		t.Error(err)

gc/option.go

@@ -4,6 +4,8 @@
 
 package gc
 
+import "time"
+
 // Option configures a garbage collector option.
 type Option func(*collector)
 
@@ -34,6 +36,15 @@ func WithThreshold(threshold int64) Option {
 	}
 }
 
+// WithMinImageAge returns an option to set the minimum
+// age a image should be to become a candidate for removal.
+// Images younger than this value won't be removed
+func WithMinImageAge(minImageAge time.Duration) Option {
+	return func(c *collector) {
+		c.minImageAge = minImageAge
+	}
+}
+
 // ReservedImages provides a list of reserved images names
 // that should not be removed.
 var ReservedImages = []string{

gc/option_test.go

@@ -7,13 +7,16 @@ package gc
 import (
 	"reflect"
 	"testing"
+	"time"
 )
 
 func TestOptions(t *testing.T) {
+	expectedMinImageAge,_ := time.ParseDuration("5h")
 	c := New(nil,
 		WithImageWhitelist([]string{"foo"}),
 		WithThreshold(42),
 		WithWhitelist([]string{"bar"}),
+		WithMinImageAge(expectedMinImageAge),
 	).(*collector)
 
 	if got, want := c.threshold, int64(42); got != want {
@@ -25,4 +28,8 @@ func TestOptions(t *testing.T) {
 	if got, want := c.reserved, []string{"foo"}; !reflect.DeepEqual(want, got) {
 		t.Errorf("Want image whitelist %v, got %v", want, got)
 	}
+
+	if got, want := c.minImageAge, expectedMinImageAge; !reflect.DeepEqual(want, got) {
+		t.Errorf("Want minImageAge %v, got %v", want, got)
+	}
 }

main.go

@@ -21,14 +21,15 @@ import (
 )
 
 type config struct {
-	Once       bool          `envconfig:"GC_ONCE"`
-	Debug      bool          `envconfig:"GC_DEBUG"`
-	Color      bool          `envconfig:"GC_DEBUG_COLOR"`
-	Pretty     bool          `envconfig:"GC_DEBUG_PRETTY"`
-	Images     []string      `envconfig:"GC_IGNORE_IMAGES"`
-	Containers []string      `envconfig:"GC_IGNORE_CONTAINERS"`
-	Interval   time.Duration `envconfig:"GC_INTERVAL" default:"5m"`
-	Cache      string        `envconfig:"GC_CACHE" default:"5gb"`
+	Once       	bool          `envconfig:"GC_ONCE"`
+	Debug      	bool          `envconfig:"GC_DEBUG"`
+	Color      	bool          `envconfig:"GC_DEBUG_COLOR"`
+	Pretty     	bool          `envconfig:"GC_DEBUG_PRETTY"`
+	Images     	[]string      `envconfig:"GC_IGNORE_IMAGES"`
+	Containers 	[]string      `envconfig:"GC_IGNORE_CONTAINERS"`
+	Interval    time.Duration `envconfig:"GC_INTERVAL" default:"5m"`
+	MinImageAge time.Duration `envconfig:"GC_MIN_IMAGE_AGE" default:"1h"`
+	Cache      	string        `envconfig:"GC_CACHE" default:"5gb"`
 }
 
 func main() {
@@ -61,6 +62,7 @@ func main() {
 		gc.WithImageWhitelist(cfg.Images),
 		gc.WithThreshold(size),
 		gc.WithWhitelist(gc.ReservedNames),
+		gc.WithMinImageAge(cfg.MinImageAge),
 		gc.WithWhitelist(cfg.Containers),
 	)
 	if cfg.Once {
@@ -71,6 +73,7 @@ func main() {
 			Strs("ignore-images", cfg.Images).
 			Str("cache", cfg.Cache).
 			Str("interval", units.HumanDuration(cfg.Interval)).
+			Str("minimal image age", units.HumanDuration(cfg.MinImageAge)).
 			Msg("starting the garbage collector")
 
 		gc.Schedule(ctx, collector, cfg.Interval)