Add structure for new exec session tracking to DB

As part of the rework of exec sessions, we need to address them
independently of containers. In the new API, we need to be able
to fetch them by their ID, regardless of what container they are
associated with. Unfortunately, our existing exec sessions are
tied to individual containers; there's no way to tell what
container a session belongs to and retrieve it without getting
every exec session for every container.

This adds a pointer to the container an exec session is
associated with to the database. The sessions themselves are
still stored in the container.

Exec-related APIs have been restructured to work with the new
database representation. The originally monolithic API has been
split into a number of smaller calls to allow more fine-grained
control of lifecycle. Support for legacy exec sessions has been
retained, but in a deprecated fashion; we should remove this in
a few releases.

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

1 files changed, 136 insertions, 2 deletions

diff --git a/libpod/in_memory_state.go b/libpod/in_memory_state.go
index 2144671a5..ca562ab7e 100644
--- a/libpod/in_memory_state.go
+++ b/libpod/in_memory_state.go
@@ -20,10 +20,16 @@ type InMemoryState struct {
 	pods map[string]*Pod
 	// Maps container ID to container struct.
 	containers map[string]*Container
-	volumes    map[string]*Volume
+	// Maps volume ID to volume struct
+	volumes map[string]*Volume
+	// Maps exec session ID to ID of associated container
+	execSessions map[string]string
 	// Maps container ID to a list of IDs of dependencies.
-	ctrDepends    map[string][]string
+	ctrDepends map[string][]string
+	// Maps volume ID to IDs of dependencies
 	volumeDepends map[string][]string
+	// Maps container ID to IDs of associated exec sessions.
+	ctrExecSessions map[string][]string
 	// Maps pod ID to a map of container ID to container struct.
 	podContainers map[string]map[string]*Container
 	// Global name registry - ensures name uniqueness and performs lookups.
@@ -51,10 +57,13 @@ func NewInMemoryState() (State, error) {
 	state.pods = make(map[string]*Pod)
 	state.containers = make(map[string]*Container)
 	state.volumes = make(map[string]*Volume)
+	state.execSessions = make(map[string]string)
 
 	state.ctrDepends = make(map[string][]string)
 	state.volumeDepends = make(map[string][]string)
 
+	state.ctrExecSessions = make(map[string][]string)
+
 	state.podContainers = make(map[string]map[string]*Container)
 
 	state.nameIndex = registrar.NewRegistrar()
@@ -316,6 +325,13 @@ func (s *InMemoryState) RemoveContainer(ctr *Container) error {
 		return errors.Wrapf(define.ErrCtrExists, "the following containers depend on container %s: %s", ctr.ID(), depsStr)
 	}
 
+	// Ensure we don't have active exec sessions
+	ctrSessions := s.ctrExecSessions[ctr.ID()]
+	if len(ctrSessions) > 0 {
+		sessStr := strings.Join(ctrSessions, ", ")
+		return errors.Wrapf(define.ErrCtrExists, "the following exec sessions are running for container %s: %s", ctr.ID(), sessStr)
+	}
+
 	if _, ok := s.containers[ctr.ID()]; !ok {
 		ctr.valid = false
 		return errors.Wrapf(define.ErrNoSuchCtr, "no container exists in state with ID %s", ctr.ID())
@@ -437,6 +453,117 @@ func (s *InMemoryState) GetContainerConfig(id string) (*ContainerConfig, error)
 	return ctr.Config(), nil
 }
 
+// Add an exec session to the database
+func (s *InMemoryState) AddExecSession(ctr *Container, session *ExecSession) error {
+	if !ctr.valid {
+		return define.ErrCtrRemoved
+	}
+	if session.ContainerID() != ctr.ID() {
+		return errors.Wrapf(define.ErrInvalidArg, "container ID and exec session ID must match")
+	}
+	if _, ok := s.containers[ctr.ID()]; !ok {
+		return define.ErrNoSuchCtr
+	}
+
+	if _, ok := s.execSessions[session.ID()]; ok {
+		return define.ErrExecSessionExists
+	}
+
+	s.execSessions[session.ID()] = ctr.ID()
+
+	ctrSessions, ok := s.ctrExecSessions[ctr.ID()]
+	if !ok {
+		ctrSessions = []string{}
+	}
+
+	ctrSessions = append(ctrSessions, session.ID())
+	s.ctrExecSessions[ctr.ID()] = ctrSessions
+
+	return nil
+}
+
+// Get an exec session from the database by full or partial ID.
+func (s *InMemoryState) GetExecSession(id string) (string, error) {
+	if id == "" {
+		return "", define.ErrEmptyID
+	}
+
+	session, ok := s.execSessions[id]
+	if !ok {
+		return "", define.ErrNoSuchExecSession
+	}
+
+	return session, nil
+}
+
+// RemoveExecSession removes an exec session from the database.
+func (s *InMemoryState) RemoveExecSession(session *ExecSession) error {
+	if _, ok := s.execSessions[session.ID()]; !ok {
+		return define.ErrNoSuchExecSession
+	}
+
+	ctrSessions, ok := s.ctrExecSessions[session.ContainerID()]
+	// If !ok - internal state seems inconsistent, but the thing we wanted
+	// to remove is gone. Continue.
+	if ok {
+		newSessions := []string{}
+		for _, sess := range ctrSessions {
+			if sess != session.ID() {
+				newSessions = append(newSessions, sess)
+			}
+		}
+		s.ctrExecSessions[session.ContainerID()] = newSessions
+	}
+
+	delete(s.execSessions, session.ID())
+
+	return nil
+}
+
+// GetContainerExecSessions retrieves all exec sessions for the given container.
+func (s *InMemoryState) GetContainerExecSessions(ctr *Container) ([]string, error) {
+	if !ctr.valid {
+		return nil, define.ErrCtrRemoved
+	}
+	if _, ok := s.containers[ctr.ID()]; !ok {
+		ctr.valid = false
+		return nil, define.ErrNoSuchCtr
+	}
+
+	ctrSessions := s.ctrExecSessions[ctr.ID()]
+
+	return ctrSessions, nil
+}
+
+// RemoveContainerExecSessions removes all exec sessions for the given
+// container.
+func (s *InMemoryState) RemoveContainerExecSessions(ctr *Container) error {
+	if !ctr.valid {
+		return define.ErrCtrRemoved
+	}
+	if _, ok := s.containers[ctr.ID()]; !ok {
+		ctr.valid = false
+		return define.ErrNoSuchCtr
+	}
+
+	ctrSessions, ok := s.ctrExecSessions[ctr.ID()]
+	if !ok {
+		return nil
+	}
+
+	for _, sess := range ctrSessions {
+		if _, ok := s.execSessions[sess]; !ok {
+			// We have an internal state inconsistency
+			// Error out
+			return errors.Wrapf(define.ErrInternal, "inconsistent database state: exec session %s is missing", sess)
+		}
+		delete(s.execSessions, sess)
+	}
+	delete(s.ctrExecSessions, ctr.ID())
+
+	return nil
+}
+
 // RewriteContainerConfig rewrites a container's configuration.
 // This function is DANGEROUS, even with an in-memory state.
 // Please read the full comment on it in state.go before using it.
@@ -1056,6 +1183,13 @@ func (s *InMemoryState) RemoveContainerFromPod(pod *Pod, ctr *Container) error {
 		return errors.Wrapf(define.ErrCtrExists, "the following containers depend on container %s: %s", ctr.ID(), depsStr)
 	}
 
+	// Ensure we don't have active exec sessions
+	ctrSessions := s.ctrExecSessions[ctr.ID()]
+	if len(ctrSessions) > 0 {
+		sessStr := strings.Join(ctrSessions, ", ")
+		return errors.Wrapf(define.ErrCtrExists, "the following exec sessions are running for container %s: %s", ctr.ID(), sessStr)
+	}
+
 	// Retrieve pod containers
 	podCtrs, ok := s.podContainers[pod.ID()]
 	if !ok {