temp: externalize CommandManager

This commit demonstrates the use of custom overlord managers by
turning the CommandManager into an external one.

internals/daemon/api_tasks.go

@@ -20,6 +20,7 @@ import (
 	"os"
 
 	"github.com/canonical/pebble/internals/logger"
+	"github.com/canonical/pebble/internals/overlord/cmdstate"
 	"github.com/canonical/pebble/internals/overlord/state"
 )
 
@@ -44,8 +45,8 @@ func v1GetTaskWebsocket(c *Command, req *http.Request, _ *UserState) Response {
 	var connect websocketConnectFunc
 	switch task.Kind() {
 	case "exec":
-		commandMgr := c.d.overlord.CommandManager()
-		connect = commandMgr.Connect
+		commandMgr := c.d.overlord.GetManagerByTag(CommandManagerTag)
+		connect = commandMgr.(*cmdstate.CommandManager).Connect
 	default:
 		logger.Noticef("Websocket %s: %q tasks do not have websockets", task.ID(), task.Kind())
 		return statusBadRequest("%q tasks do not have websockets", task.Kind())

internals/daemon/daemon.go

@@ -39,13 +39,18 @@ import (
 	"github.com/canonical/pebble/internals/osutil/sys"
 	"github.com/canonical/pebble/internals/overlord"
 	"github.com/canonical/pebble/internals/overlord/checkstate"
+	"github.com/canonical/pebble/internals/overlord/cmdstate"
 	"github.com/canonical/pebble/internals/overlord/restart"
 	"github.com/canonical/pebble/internals/overlord/servstate"
 	"github.com/canonical/pebble/internals/overlord/standby"
 	"github.com/canonical/pebble/internals/overlord/state"
 	"github.com/canonical/pebble/internals/systemd"
 )
 
+const (
+	CommandManagerTag = 1
+)
+
 var (
 	// ManagerGenerators passes build functions to create external managers.
 	//
@@ -789,6 +794,13 @@ func New(opts *Options) (*Daemon, error) {
 		httpAddress:         opts.HTTPAddress,
 	}
 
+	ManagerGenerators = append(
+		ManagerGenerators,
+		func(o *overlord.Overlord) (overlord.ManagerTag, overlord.StateManager) {
+			commandMgr := cmdstate.NewManager(o.TaskRunner())
+			return CommandManagerTag, commandMgr
+		})
+
 	ovld, err := overlord.New(opts.Dir, d, opts.ServiceOutput, ManagerGenerators)
 	if err == errExpectedReboot {
 		// we proceed without overlord until we reach Stop

internals/overlord/overlord.go

@@ -29,7 +29,6 @@ import (
 
 	"github.com/canonical/pebble/internals/osutil"
 	"github.com/canonical/pebble/internals/overlord/checkstate"
-	"github.com/canonical/pebble/internals/overlord/cmdstate"
 	"github.com/canonical/pebble/internals/overlord/logstate"
 	"github.com/canonical/pebble/internals/overlord/patch"
 	"github.com/canonical/pebble/internals/overlord/restart"
@@ -73,7 +72,6 @@ type Overlord struct {
 	inited         bool
 	runner         *state.TaskRunner
 	serviceMgr     *servstate.ServiceManager
-	commandMgr     *cmdstate.CommandManager
 	checkMgr       *checkstate.CheckManager
 	logMgr         *logstate.LogManager
 	customManagers map[ManagerTag]StateManager
@@ -134,9 +132,6 @@ func New(
 	}
 	o.addManager(o.serviceMgr)
 
-	o.commandMgr = cmdstate.NewManager(o.runner)
-	o.addManager(o.commandMgr)
-
 	o.checkMgr = checkstate.NewManager()
 
 	// Tell check manager about plan updates.
@@ -433,12 +428,6 @@ func (o *Overlord) ServiceManager() *servstate.ServiceManager {
 	return o.serviceMgr
 }
 
-// CommandManager returns the command manager responsible for executing
-// commands under the overlord.
-func (o *Overlord) CommandManager() *cmdstate.CommandManager {
-	return o.commandMgr
-}
-
 // CheckManager returns the check manager responsible for running health
 // checks under the overlord.
 func (o *Overlord) CheckManager() *checkstate.CheckManager {