Basic version of libcontainer API.

This version has mostly the behavior available today and the
functionality agreed upon in other PRs. Further changes will be sent as
smaller PRs for discussion.

Docker-DCO-1.1-Signed-off-by: Victor Marmol <vmarmol@google.com> (github: vmarmol)

api.go

@@ -1,23 +1,150 @@
+/*
+API for libcontainer.
+
+NOTE: The API is in flux and mainly not implemented. Proceed with caution until further notice.
+*/
 package libcontainer
 
 import (
-	"github.com/docker/libcontainer/cgroups/fs"
-	"github.com/docker/libcontainer/network"
+	"io"
 )
 
-// Returns all available stats for the given container.
-func GetStats(container *Config, state *State) (*ContainerStats, error) {
-	var containerStats ContainerStats
-	stats, err := fs.GetStats(container.Cgroups)
-	if err != nil {
-		return &containerStats, err
-	}
-	containerStats.CgroupStats = stats
-	networkStats, err := network.GetStats(&state.NetworkState)
-	if err != nil {
-		return &containerStats, err
-	}
-	containerStats.NetworkStats = networkStats
+// Name of a container.
+//
+// Allowable characters for container names are:
+// - Alpha numeric ([a-zA-Z0-9])
+// - Underscores (_)
+type Name string
 
-	return &containerStats, nil
+// The running state of the container.
+type RunState int
+
+const (
+	// The container exists and is running.
+	RUNNING RunState = iota
+
+	// The container exists, it is in the process of being paused.
+	PAUSING RunState = iota
+
+	// The container exists, but all its processes are paused.
+	PAUSED RunState = iota
+
+	// The container does not exist.
+	DESTROYED RunState = iota
+)
+
+// Configuration for a process to be run inside a container.
+type ProcessConfig struct {
+	// The command to be run followed by any arguments.
+	Args []string
+
+	// Map of environment variables to their values.
+	Env []string
+
+	// Stdin is a pointer to a reader which provides the standard input stream.
+	// Stdout is a pointer to a writer which receives the standard output stream.
+	// Stderr is a pointer to a writer which receives the standard error stream.
+	//
+	// If a reader or writer is nil, the input stream is assumed to be empty and the output is
+	// discarded.
+	//
+	// The readers and writers, if supplied, are closed when the process terminates. Their Close
+	// methods should be idempotent.
+	//
+	// Stdout and Stderr may refer to the same writer in which case the output is interspersed.
+	Stdin  *io.ReadCloser
+	Stdout *io.WriteCloser
+	Stderr *io.WriteCloser
+
+	// TODO(vmarmol): Complete.
+	// ProcessConfig take over some of the runtime config from Config.
+	// This is anything that can be set per-process that enters the container and its namespaces.
+	//
+	// Things like:
+	// - Namespaces
+	// - Capabilities
+	// - User/Groups
+	// - Working directory
+}
+
+// Factory of libcontainer containers.
+type Factory interface {
+	// Creates a new container as specified, and starts an init process inside.
+	//
+	// The container and PID of the init process is returned. The init must be reaped by the caller.
+	//
+	// Errors: name already exists,
+	//         config or initialConfig invalid,
+	//         system error.
+	//
+	// Arguments:
+	//   name: The user-provided name of the container. Used to identify this container, must be unique
+	//         in this machine.
+	//   config: The configuration of the new container.
+	//   initialProcess: The configuration of the init to run inside the container.
+	//
+	// On error, any partially created container parts are cleaned up (the operation is atomic).
+	Create(name Name, config *Config, initialProcess *ProcessConfig) (*Container, int, error)
+}
+
+// A libcontainer container object. Must be created by the Factory above.
+//
+// Each container is thread-safe within the same process. Since a container can
+// be destroyed by a separate process, any function may return that the container
+// was not found.
+type Container interface {
+	// Returns the name of this container.
+	Name() Name
+
+	// Returns the current run state of the container.
+	//
+	// Errors: container no longer exists,
+	//         system error.
+	RunState() (RunState, error)
+
+	// Returns the current config of the container.
+	//
+	// Errors: container no longer exists,
+	//         system error.
+	Config() (*Config, error)
+
+	// Destroys the container after killing all running processes.
+	//
+	// Any event registrations are removed before the container is destroyed.
+	// No error is returned if the container is already destroyed.
+	//
+	// Errors: system error.
+	Destroy() error
+
+	// Returns the PIDs inside this container. The PIDs are in the namespace of the calling process.
+	//
+	// Errors: container no longer exists,
+	//         system error.
+	//
+	// Some of the returned PIDs may no longer refer to processes in the Container, unless
+	// the Container state is PAUSED in which case every PID in the slice is valid.
+	Processes() ([]int, error)
+
+	// Returns statistics for the container.
+	//
+	// Errors: container no longer exists,
+	//         system error.
+	Stats() (*ContainerStats, error)
+
+	// If the Container state is RUNNING or PAUSING, sets the Container state to PAUSING and pauses
+	// the execution of any user processes. Asynchronously, when the container finished being paused the
+	// state is changed to PAUSED.
+	// If the Container state is PAUSED, do nothing.
+	//
+	// Errors: container no longer exists,
+	//         system error.
+	Pause() error
+
+	// If the Container state is PAUSED, resumes the execution of any user processes in the
+	// Container before setting the Container state to RUNNING.
+	// If the Container state is RUNNING, do nothing.
+	//
+	// Errors: container no longer exists,
+	//         system error.
+	Resume() error
 }

api_temp.go

@@ -0,0 +1,29 @@
+/*
+Temporary API endpoint for libcontainer while the full API is finalized (api.go).
+*/
+package libcontainer
+
+import (
+	"github.com/docker/libcontainer/cgroups/fs"
+	"github.com/docker/libcontainer/network"
+)
+
+// TODO(vmarmol): Complete Stats() in final libcontainer API and move users to that.
+// DEPRECATED: The below portions are only to be used during the transition to the official API.
+
+// Returns all available stats for the given container.
+func GetStats(container *Config, state *State) (*ContainerStats, error) {
+	var containerStats ContainerStats
+	stats, err := fs.GetStats(container.Cgroups)
+	if err != nil {
+		return &containerStats, err
+	}
+	containerStats.CgroupStats = stats
+	networkStats, err := network.GetStats(&state.NetworkState)
+	if err != nil {
+		return &containerStats, err
+	}
+	containerStats.NetworkStats = networkStats
+
+	return &containerStats, nil
+}