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authorMatthew Heon <matthew.heon@pm.me>2021-03-02 11:58:32 -0500
committerMatthew Heon <matthew.heon@pm.me>2021-03-02 13:30:28 -0500
commit43e899c2ec2a874b9cb16f42bfd1e676981353b1 (patch)
treec8a42515aae42c0f50767323ed849ccbc8c2b2d5 /libpod
parent426178a49991106ffe222f12cc42409ae78dd257 (diff)
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Rewrite Rename backend in a more atomic fashion
Move the core of renaming logic into the DB. This guarantees a lot more atomicity than we have right now (our current solution, removing the container from the DB and re-creating it, is *VERY* not atomic and prone to leaving a corrupted state behind if things go wrong. Moving things into the DB allows us to remove most, but not all, of this - there's still a potential scenario where the c/storage rename fails but the Podman rename succeeds, and we end up with a mismatched state. Signed-off-by: Matthew Heon <matthew.heon@pm.me>
Diffstat (limited to 'libpod')
-rw-r--r--libpod/boltdb_state.go98
-rw-r--r--libpod/in_memory_state.go40
-rw-r--r--libpod/runtime_ctr.go113
-rw-r--r--libpod/state.go13
4 files changed, 166 insertions, 98 deletions
diff --git a/libpod/boltdb_state.go b/libpod/boltdb_state.go
index 6f2eaeab2..122dd080f 100644
--- a/libpod/boltdb_state.go
+++ b/libpod/boltdb_state.go
@@ -1681,6 +1681,104 @@ func (s *BoltState) RewriteContainerConfig(ctr *Container, newCfg *ContainerConf
return err
}
+// SafeRewriteContainerConfig rewrites a container's configuration in a more
+// limited fashion than RewriteContainerConfig. It is marked as safe to use
+// under most circumstances, unlike RewriteContainerConfig.
+// DO NOT USE TO: Change container dependencies, change pod membership, change
+// locks, change container ID.
+func (s *BoltState) SafeRewriteContainerConfig(ctr *Container, oldName, newName string, newCfg *ContainerConfig) error {
+ if !s.valid {
+ return define.ErrDBClosed
+ }
+
+ if !ctr.valid {
+ return define.ErrCtrRemoved
+ }
+
+ if newName != "" && newCfg.Name != newName {
+ return errors.Wrapf(define.ErrInvalidArg, "new name %s for container %s must match name in given container config", newName, ctr.ID())
+ }
+ if newName != "" && oldName == "" {
+ return errors.Wrapf(define.ErrInvalidArg, "must provide old name for container if a new name is given")
+ }
+
+ newCfgJSON, err := json.Marshal(newCfg)
+ if err != nil {
+ return errors.Wrapf(err, "error marshalling new configuration JSON for container %s", ctr.ID())
+ }
+
+ db, err := s.getDBCon()
+ if err != nil {
+ return err
+ }
+ defer s.deferredCloseDBCon(db)
+
+ err = db.Update(func(tx *bolt.Tx) error {
+ if newName != "" {
+ idBkt, err := getIDBucket(tx)
+ if err != nil {
+ return err
+ }
+ namesBkt, err := getNamesBucket(tx)
+ if err != nil {
+ return err
+ }
+ allCtrsBkt, err := getAllCtrsBucket(tx)
+ if err != nil {
+ return err
+ }
+
+ needsRename := true
+ if exists := namesBkt.Get([]byte(newName)); exists != nil {
+ if string(exists) == ctr.ID() {
+ // Name already associated with the ID
+ // of this container. No need for a
+ // rename.
+ needsRename = false
+ } else {
+ return errors.Wrapf(define.ErrCtrExists, "name %s already in use, cannot rename container %s", newName, ctr.ID())
+ }
+ }
+
+ if needsRename {
+ // We do have to remove the old name. The other
+ // buckets are ID-indexed so we just need to
+ // overwrite the values there.
+ if err := namesBkt.Delete([]byte(oldName)); err != nil {
+ return errors.Wrapf(err, "error deleting container %s old name from DB for rename", ctr.ID())
+ }
+ if err := idBkt.Put([]byte(ctr.ID()), []byte(newName)); err != nil {
+ return errors.Wrapf(err, "error renaming container %s in ID bucket in DB", ctr.ID())
+ }
+ if err := namesBkt.Put([]byte(newName), []byte(ctr.ID())); err != nil {
+ return errors.Wrapf(err, "error adding new name %s for container %s in DB", newName, ctr.ID())
+ }
+ if err := allCtrsBkt.Put([]byte(ctr.ID()), []byte(newName)); err != nil {
+ return errors.Wrapf(err, "error renaming container %s in all containers bucket in DB", ctr.ID())
+ }
+ }
+ }
+
+ ctrBkt, err := getCtrBucket(tx)
+ if err != nil {
+ return err
+ }
+
+ ctrDB := ctrBkt.Bucket([]byte(ctr.ID()))
+ if ctrDB == nil {
+ ctr.valid = false
+ return errors.Wrapf(define.ErrNoSuchCtr, "no container with ID %s found in DB", ctr.ID())
+ }
+
+ if err := ctrDB.Put(configKey, newCfgJSON); err != nil {
+ return errors.Wrapf(err, "error updating container %s config JSON", ctr.ID())
+ }
+
+ return nil
+ })
+ 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.
diff --git a/libpod/in_memory_state.go b/libpod/in_memory_state.go
index 26f15d9c8..3875878ed 100644
--- a/libpod/in_memory_state.go
+++ b/libpod/in_memory_state.go
@@ -822,6 +822,46 @@ func (s *InMemoryState) RewriteContainerConfig(ctr *Container, newCfg *Container
return nil
}
+// SafeRewriteContainerConfig rewrites a container's configuration.
+// It's safer than RewriteContainerConfig, but still has limitations. Please
+// read the comment in state.go before using.
+func (s *InMemoryState) SafeRewriteContainerConfig(ctr *Container, oldName, newName string, newCfg *ContainerConfig) error {
+ if !ctr.valid {
+ return define.ErrCtrRemoved
+ }
+
+ if _, err := s.nameIndex.Get(newName); err == nil {
+ return errors.Wrapf(define.ErrCtrExists, "name %s is in use", newName)
+ }
+
+ // If the container does not exist, return error
+ stateCtr, ok := s.containers[ctr.ID()]
+ if !ok {
+ ctr.valid = false
+ return errors.Wrapf(define.ErrNoSuchCtr, "container with ID %s not found in state", ctr.ID())
+ }
+
+ // Change name in registry.
+ if s.namespace != "" {
+ nsIndex, ok := s.namespaceIndexes[s.namespace]
+ if !ok {
+ return define.ErrInternal
+ }
+ nsIndex.nameIndex.Release(oldName)
+ if err := nsIndex.nameIndex.Reserve(newName, ctr.ID()); err != nil {
+ return errors.Wrapf(err, "error registering name %s", newName)
+ }
+ }
+ s.nameIndex.Release(oldName)
+ if err := s.nameIndex.Reserve(newName, ctr.ID()); err != nil {
+ return errors.Wrapf(err, "error registering name %s", newName)
+ }
+
+ stateCtr.config = newCfg
+
+ 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.
diff --git a/libpod/runtime_ctr.go b/libpod/runtime_ctr.go
index 8bf862bf2..301c4627d 100644
--- a/libpod/runtime_ctr.go
+++ b/libpod/runtime_ctr.go
@@ -74,8 +74,7 @@ func (r *Runtime) RestoreContainer(ctx context.Context, rSpec *spec.Spec, config
}
// RenameContainer renames the given container.
-// The given container object will be rendered unusable, and a new, renamed
-// Container will be returned.
+// Returns a copy of the container that has been renamed if successful.
func (r *Runtime) RenameContainer(ctx context.Context, ctr *Container, newName string) (*Container, error) {
ctr.lock.Lock()
defer ctr.lock.Unlock()
@@ -88,26 +87,6 @@ func (r *Runtime) RenameContainer(ctx context.Context, ctr *Container, newName s
return nil, define.RegexError
}
- // Check if the name is available.
- // This is *100% NOT ATOMIC* so any failures in-flight will do
- // *VERY BAD THINGS* to the state. So we have to try and catch all we
- // can before starting.
- if _, err := r.state.LookupContainerID(newName); err == nil {
- return nil, errors.Wrapf(define.ErrCtrExists, "name %s is already in use by another container", newName)
- }
- if _, err := r.state.LookupPod(newName); err == nil {
- return nil, errors.Wrapf(define.ErrPodExists, "name %s is already in use by another pod", newName)
- }
-
- // TODO: Investigate if it is possible to remove this limitation.
- depCtrs, err := r.state.ContainerInUse(ctr)
- if err != nil {
- return nil, err
- }
- if len(depCtrs) > 0 {
- return nil, errors.Wrapf(define.ErrCtrExists, "cannot rename container %s as it is in use by other containers: %v", ctr.ID(), strings.Join(depCtrs, ","))
- }
-
// We need to pull an updated config, in case another rename fired and
// the config was re-written.
newConf, err := r.state.GetContainerConfig(ctr.ID())
@@ -116,95 +95,33 @@ func (r *Runtime) RenameContainer(ctx context.Context, ctr *Container, newName s
}
ctr.config = newConf
- // TODO: This is going to fail if we have active exec sessions, too.
- // Investigate fixing that at a later date.
-
- var pod *Pod
- if ctr.config.Pod != "" {
- tmpPod, err := r.state.Pod(ctr.config.Pod)
- if err != nil {
- return nil, errors.Wrapf(err, "error retrieving container %s pod", ctr.ID())
- }
- pod = tmpPod
- // Lock pod to ensure it's not removed while we're working
- pod.lock.Lock()
- defer pod.lock.Unlock()
- }
-
- // Lock all volumes to ensure they are not removed while we're working
- volsLocked := make(map[string]bool)
- for _, namedVol := range ctr.config.NamedVolumes {
- if volsLocked[namedVol.Name] {
- continue
- }
- vol, err := r.state.Volume(namedVol.Name)
- if err != nil {
- return nil, errors.Wrapf(err, "error retrieving volume used by container %s", ctr.ID())
- }
-
- volsLocked[vol.Name()] = true
- vol.lock.Lock()
- defer vol.lock.Unlock()
- }
-
logrus.Infof("Going to rename container %s from %q to %q", ctr.ID(), ctr.Name(), newName)
- // Step 1: remove the old container.
- if pod != nil {
- if err := r.state.RemoveContainerFromPod(pod, ctr); err != nil {
- return nil, errors.Wrapf(err, "error renaming container %s", ctr.ID())
- }
- } else {
- if err := r.state.RemoveContainer(ctr); err != nil {
- return nil, errors.Wrapf(err, "error renaming container %s", ctr.ID())
- }
- }
-
- // Step 2: Make a new container based on the old one.
- // TODO: Should we deep-copy the container config and state, to be safe?
- newCtr := new(Container)
- newCtr.config = ctr.config
- newCtr.state = ctr.state
- newCtr.lock = ctr.lock
- newCtr.ociRuntime = ctr.ociRuntime
- newCtr.runtime = r
- newCtr.rootlessSlirpSyncR = ctr.rootlessSlirpSyncR
- newCtr.rootlessSlirpSyncW = ctr.rootlessSlirpSyncW
- newCtr.rootlessPortSyncR = ctr.rootlessPortSyncR
- newCtr.rootlessPortSyncW = ctr.rootlessPortSyncW
-
- newCtr.valid = true
- newCtr.config.Name = newName
-
- // Step 3: Add that new container to the DB
- if pod != nil {
- if err := r.state.AddContainerToPod(pod, newCtr); err != nil {
- return nil, errors.Wrapf(err, "error renaming container %s", newCtr.ID())
- }
- } else {
- if err := r.state.AddContainer(newCtr); err != nil {
- return nil, errors.Wrapf(err, "error renaming container %s", newCtr.ID())
- }
- }
+ // Step 1: Alter the config. Save the old name, we need it to rewrite
+ // the config.
+ oldName := ctr.config.Name
+ ctr.config.Name = newName
- // Step 4: Save the new container, to force the state to be written to
- // the DB. This may not be necessary, depending on DB implementation,
- // but let's do it to be safe.
- if err := newCtr.save(); err != nil {
- return nil, err
+ // Step 2: rewrite the old container's config in the DB.
+ if err := r.state.SafeRewriteContainerConfig(ctr, oldName, ctr.config.Name, ctr.config); err != nil {
+ // Assume the rename failed.
+ // Set config back to the old name so reflect what is actually
+ // present in the DB.
+ ctr.config.Name = oldName
+ return nil, errors.Wrapf(err, "error renaming container %s", ctr.ID())
}
- // Step 5: rename the container in c/storage.
+ // Step 3: rename the container in c/storage.
// This can fail if the name is already in use by a non-Podman
// container. This puts us in a bad spot - we've already renamed the
// container in Podman. We can swap the order, but then we have the
// opposite problem. Atomicity is a real problem here, with no easy
// solution.
- if err := r.store.SetNames(newCtr.ID(), []string{newCtr.Name()}); err != nil {
+ if err := r.store.SetNames(ctr.ID(), []string{ctr.Name()}); err != nil {
return nil, err
}
- return newCtr, nil
+ return ctr, nil
}
func (r *Runtime) initContainerVariables(rSpec *spec.Spec, config *ContainerConfig) (*Container, error) {
diff --git a/libpod/state.go b/libpod/state.go
index 074d21740..4b711bae9 100644
--- a/libpod/state.go
+++ b/libpod/state.go
@@ -155,6 +155,19 @@ type State interface {
// answer is this: use this only very sparingly, and only if you really
// know what you're doing.
RewriteContainerConfig(ctr *Container, newCfg *ContainerConfig) error
+ // This is a more limited version of RewriteContainerConfig, though it
+ // comes with the added ability to alter a container's name. In exchange
+ // it loses the ability to manipulate the container's locks.
+ // It is not intended to be as restrictive as RewriteContainerConfig, in
+ // that we allow it to be run while other Podman processes are running,
+ // and without holding the alive lock.
+ // Container ID and pod membership still *ABSOLUTELY CANNOT* be altered.
+ // Also, you cannot change a container's dependencies - shared namespace
+ // containers or generic dependencies - at present. This is
+ // theoretically possible but not yet implemented.
+ // If newName is not "" the container will be renamed to the new name.
+ // The oldName parameter is only required if newName is given.
+ SafeRewriteContainerConfig(ctr *Container, oldName, newName string, newCfg *ContainerConfig) error
// PLEASE READ THE DESCRIPTION FOR RewriteContainerConfig BEFORE USING.
// This function is identical to RewriteContainerConfig, save for the
// fact that it is used with pods instead.