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, 26 insertions, 0 deletions

diff --git a/libpod/state.go b/libpod/state.go
index b246b5eac..9690e5819 100644
--- a/libpod/state.go
+++ b/libpod/state.go
@@ -72,6 +72,8 @@ type State interface {
 	// Removes container from state.
 	// Containers that are part of pods must use RemoveContainerFromPod.
 	// The container must be part of the set namespace.
+	// All dependencies must be removed first.
+	// All exec sessions referencing the container must be removed first.
 	RemoveContainer(ctr *Container) error
 	// UpdateContainer updates a container's state from the backing store.
 	// The container must be part of the set namespace.
@@ -95,6 +97,30 @@ type State interface {
 	// Return a container config from the database by full ID
 	GetContainerConfig(id string) (*ContainerConfig, error)
 
+	// Add creates a reference to an exec session in the database.
+	// The container the exec session is attached to will be recorded.
+	// The container state will not be modified.
+	// The actual exec session itself is part of the container's state.
+	// We assume higher-level callers will add the session by saving the
+	// container's state before calling this. This only ensures that the ID
+	// of the exec session is associated with the ID of the container.
+	// Implementations may, but are not required to, verify that the state
+	// of the given container has an exec session with the ID given.
+	AddExecSession(ctr *Container, session *ExecSession) error
+	// Get retrieves the container a given exec session is attached to.
+	GetExecSession(id string) (string, error)
+	// Remove a reference to an exec session from the database.
+	// This will not modify container state to remove the exec session there
+	// and instead only removes the session ID -> container ID reference
+	// added by AddExecSession.
+	RemoveExecSession(session *ExecSession) error
+	// Get the IDs of all exec sessions attached to a given container.
+	GetContainerExecSessions(ctr *Container) ([]string, error)
+	// Remove all exec sessions for a single container.
+	// Usually used as part of removing the container.
+	// As with RemoveExecSession, container state will not be modified.
+	RemoveContainerExecSessions(ctr *Container) error
+
 	// PLEASE READ FULL DESCRIPTION BEFORE USING.
 	// Rewrite a container's configuration.
 	// This function breaks libpod's normal prohibition on a read-only