Remove container lifecycle image ref dependency.

Signed-off-by: Lantao Liu <lantaol@google.com>

pkg/store/container/container_test.go

@@ -39,8 +39,9 @@ func TestContainerStore(t *testing.T) {
 					Attempt: 1,
 				},
 			},
-			ImageRef: "TestImage-1",
-			LogPath:  "/test/log/path/1",
+			ImageRef:   "TestImage-1",
+			StopSignal: "SIGTERM",
+			LogPath:    "/test/log/path/1",
 		},
 		"2abcd": {
 			ID:        "2abcd",
@@ -52,8 +53,9 @@ func TestContainerStore(t *testing.T) {
 					Attempt: 2,
 				},
 			},
-			ImageRef: "TestImage-2",
-			LogPath:  "/test/log/path/2",
+			StopSignal: "SIGTERM",
+			ImageRef:   "TestImage-2",
+			LogPath:    "/test/log/path/2",
 		},
 		"4a333": {
 			ID:        "4a333",
@@ -65,8 +67,9 @@ func TestContainerStore(t *testing.T) {
 					Attempt: 3,
 				},
 			},
-			ImageRef: "TestImage-3",
-			LogPath:  "/test/log/path/3",
+			StopSignal: "SIGTERM",
+			ImageRef:   "TestImage-3",
+			LogPath:    "/test/log/path/3",
 		},
 		"4abcd": {
 			ID:        "4abcd",
@@ -78,7 +81,8 @@ func TestContainerStore(t *testing.T) {
 					Attempt: 1,
 				},
 			},
-			ImageRef: "TestImage-4abcd",
+			StopSignal: "SIGTERM",
+			ImageRef:   "TestImage-4abcd",
 		},
 	}
 	statuses := map[string]Status{
@@ -182,8 +186,9 @@ func TestWithContainerIO(t *testing.T) {
 				Attempt: 1,
 			},
 		},
-		ImageRef: "TestImage-1",
-		LogPath:  "/test/log/path",
+		ImageRef:   "TestImage-1",
+		StopSignal: "SIGTERM",
+		LogPath:    "/test/log/path",
 	}
 	status := Status{
 		Pid:        1,

pkg/store/container/metadata.go

@@ -27,7 +27,7 @@ import (
 // 1) Metadata is immutable after created.
 // 2) Metadata is checkpointed as containerd container label.
 
-// metadataVersion  is current version of container metadata.
+// metadataVersion is current version of container metadata.
 const metadataVersion = "v1" // nolint
 
 // versionedMetadata is the internal versioned container metadata.
@@ -58,6 +58,9 @@ type Metadata struct {
 	ImageRef string
 	// LogPath is the container log path.
 	LogPath string
+	// StopSignal is the system call signal that will be sent to the container to exit.
+	// TODO(random-liu): Add integration test for stop signal.
+	StopSignal string
 }
 
 // MarshalJSON encodes Metadata into bytes in json format.