Add ability to rewrite pod configs in the database

Necessary for rewriting lock IDs as part of renumber.

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

libpod/boltdb_state.go

@@ -827,6 +827,50 @@ func (s *BoltState) RewriteContainerConfig(ctr *Container, newCfg *ContainerConf
 	return err
 }
 
+// RewritePodConfig rewrites a pod's configuration.
+// WARNING: This function is DANGEROUS. Do not use without reading the full
+// comment on this function in state.go.
+func (s *BoltState) RewritePodConfig(pod *Pod, newCfg *PodConfig) error {
+	if !s.valid {
+		return ErrDBClosed
+	}
+
+	if !pod.valid {
+		return ErrPodRemoved
+	}
+
+	newCfgJSON, err := json.Marshal(newCfg)
+	if err != nil {
+		return errors.Wrapf(err, "error marshalling new configuration JSON for container %s", pod.ID())
+	}
+
+	db, err := s.getDBCon()
+	if err != nil {
+		return err
+	}
+	defer s.closeDBCon(db)
+
+	err = db.Update(func(tx *bolt.Tx) error {
+		podBkt, err := getPodBucket(tx)
+		if err != nil {
+			return err
+		}
+
+		podDB := podBkt.Bucket([]byte(pod.ID()))
+		if podDB == nil {
+			pod.valid = false
+			return errors.Wrapf(ErrNoSuchPod, "no pod with ID %s found in DB", pod.ID())
+		}
+
+		if err := podDB.Put(configKey, newCfgJSON); err != nil {
+			return errors.Wrapf(err, "error updating pod %s config JSON", pod.ID())
+		}
+
+		return nil
+	})
+	return err
+}
+
 // Pod retrieves a pod given its full ID
 func (s *BoltState) Pod(id string) (*Pod, error) {
 	if id == "" {

libpod/in_memory_state.go

@@ -410,6 +410,26 @@ func (s *InMemoryState) RewriteContainerConfig(ctr *Container, newCfg *Container
 	return nil
 }
 
+// RewritePodConfig rewrites a pod's configuration.
+// This function is DANGEROUS, even with in-memory state.
+// Please read the full comment on it in state.go before using it.
+func (s *InMemoryState) RewritePodConfig(pod *Pod, newCfg *PodConfig) error {
+	if !pod.valid {
+		return ErrPodRemoved
+	}
+
+	// If the pod does not exist, return error
+	statePod, ok := s.pods[pod.ID()]
+	if !ok {
+		pod.valid = false
+		return errors.Wrapf(ErrNoSuchPod, "pod with ID %s not found in state", pod.ID())
+	}
+
+	statePod.config = newCfg
+
+	return nil
+}
+
 // Volume retrieves a volume from its full name
 func (s *InMemoryState) Volume(name string) (*Volume, error) {
 	if name == "" {

libpod/state.go

@@ -107,10 +107,19 @@ type State interface {
 	// newer, but identical, configuration fields), or during libpod init
 	// WHILE HOLDING THE ALIVE LOCK (to prevent other libpod instances from
 	// being initialized).
+	// Most things in config can be changed by this, but container ID and
+	// name ABSOLUTELY CANNOT BE ALTERED. If you do so, there is a high
+	// potential for database corruption.
 	// There are a lot of capital letters and conditions here, but the short
 	// answer is this: use this only very sparingly, and only if you really
 	// know what you're doing.
 	RewriteContainerConfig(ctr *Container, newCfg *ContainerConfig) error
+	// PLEASE READ THE ABOVE DESCRIPTION BEFORE USING.
+	// This function is identical to RewriteContainerConfig, save for the
+	// fact that it is used with pods instead.
+	// It is subject to the same conditions as RewriteContainerConfig.
+	// Please do not use this unless you know what you're doing.
+	RewritePodConfig(pod *Pod, newCfg *PodConfig) error
 
 	// Accepts full ID of pod.
 	// If the pod given is not in the set namespace, an error will be

libpod/state_test.go

@@ -1334,6 +1334,42 @@ func TestRewriteContainerConfigRewritesConfig(t *testing.T) {
 	})
 }
 
+func TestRewritePodConfigDoesNotExist(t *testing.T) {
+	runForAllStates(t, func(t *testing.T, state State, manager lock.Manager) {
+		err := state.RewritePodConfig(&Pod{}, &PodConfig{})
+		assert.Error(t, err)
+	})
+}
+
+func TestRewritePodConfigNotInState(t *testing.T) {
+	runForAllStates(t, func(t *testing.T, state State, manager lock.Manager) {
+		testPod, err := getTestPod1(manager)
+		assert.NoError(t, err)
+		err = state.RewritePodConfig(testPod, &PodConfig{})
+		assert.Error(t, err)
+	})
+}
+
+func TestRewritePodConfigRewritesConfig(t *testing.T) {
+	runForAllStates(t, func(t *testing.T, state State, manager lock.Manager) {
+		testPod, err := getTestPod1(manager)
+		assert.NoError(t, err)
+
+		err = state.AddPod(testPod)
+		assert.NoError(t, err)
+
+		testPod.config.CgroupParent = "/another_cgroup_parent"
+
+		err = state.RewritePodConfig(testPod, testPod.config)
+		assert.NoError(t, err)
+
+		testPodFromState, err := state.Pod(testPod.ID())
+		assert.NoError(t, err)
+
+		testPodsEqual(t, testPodFromState, testPod, true)
+	})
+}
+
 func TestGetPodDoesNotExist(t *testing.T) {
 	runForAllStates(t, func(t *testing.T, state State, manager lock.Manager) {
 		_, err := state.Pod("doesnotexist")