Adds DrainConnectionsTimeout microcluster configuration (#867)

In microcluster, there is now a configuration that allows us to drain
any current connections before shutting down the unix / http servers.

Note that the servers will also be shut down when removing a node, or if
bootstrapping or joining a node fails. If we're not waiting for the
connection to drain, we may close current connections before managing to
write a response to the clients, resulting in them getting EOF errors.

Adds the --disable-update-node-config-controller k8sd flag, with 10s as
the default value.

src/k8s/cmd/k8sd/k8sd.go

@@ -1,6 +1,8 @@
 package k8sd
 
 import (
+	"time"
+
 	cmdutil "github.com/canonical/k8s/cmd/util"
 	"github.com/canonical/k8s/pkg/k8sd/app"
 	"github.com/canonical/k8s/pkg/log"
@@ -19,6 +21,7 @@ var rootCmdOpts struct {
 	disableFeatureController            bool
 	disableUpdateNodeConfigController   bool
 	disableCSRSigningController         bool
+	drainConnectionsTimeout             time.Duration
 }
 
 func addCommands(root *cobra.Command, group *cobra.Group, commands ...*cobra.Command) {
@@ -55,6 +58,7 @@ func NewRootCmd(env cmdutil.ExecutionEnvironment) *cobra.Command {
 				DisableUpdateNodeConfigController:   rootCmdOpts.disableUpdateNodeConfigController,
 				DisableFeatureController:            rootCmdOpts.disableFeatureController,
 				DisableCSRSigningController:         rootCmdOpts.disableCSRSigningController,
+				DrainConnectionsTimeout:             rootCmdOpts.drainConnectionsTimeout,
 			})
 			if err != nil {
 				cmd.PrintErrf("Error: Failed to initialize k8sd: %v", err)
@@ -88,6 +92,7 @@ func NewRootCmd(env cmdutil.ExecutionEnvironment) *cobra.Command {
 
 	cmd.Flags().Uint("port", 0, "Default port for the HTTP API")
 	cmd.Flags().MarkDeprecated("port", "this flag does not have any effect, and will be removed in a future version")
+	cmd.Flags().DurationVar(&rootCmdOpts.drainConnectionsTimeout, "drain-connection-timeout", 10*time.Second, "amount of time to allow for all connections to drain when shutting down")
 
 	cmd.AddCommand(newSqlCmd(env))
 

src/k8s/pkg/k8sd/api/endpoints.go

@@ -3,6 +3,7 @@ package api
 
 import (
 	"context"
+	"time"
 
 	apiv1 "github.com/canonical/k8s-snap-api/api/v1"
 	"github.com/canonical/microcluster/v2/rest"
@@ -15,7 +16,7 @@ type Endpoints struct {
 
 // New creates a new API server instance.
 // Context is the context to use for the API servers endpoints.
-func New(ctx context.Context, provider Provider) map[string]rest.Server {
+func New(ctx context.Context, provider Provider, drainConnectionsTimeout time.Duration) map[string]rest.Server {
 	k8sd := &Endpoints{
 		context:  ctx,
 		provider: provider,
@@ -31,6 +32,7 @@ func New(ctx context.Context, provider Provider) map[string]rest.Server {
 					Endpoints:  k8sd.Endpoints(),
 				},
 			},
+			DrainConnectionsTimeout: drainConnectionsTimeout,
 		},
 	}
 }

src/k8s/pkg/k8sd/app/app.go

@@ -45,6 +45,8 @@ type Config struct {
 	DisableFeatureController bool
 	// DisableCSRSigningController is a bool flag to disable csrsigning controller.
 	DisableCSRSigningController bool
+	// DrainConnectionsTimeout is the amount of time to allow for all connections to drain when shutting down.
+	DrainConnectionsTimeout time.Duration
 }
 
 // App is the k8sd microcluster instance.
@@ -232,12 +234,13 @@ func (a *App) Run(ctx context.Context, customHooks *state.Hooks) error {
 	}
 
 	err := a.cluster.Start(ctx, microcluster.DaemonArgs{
-		Version:          string(apiv1.K8sdAPIVersion),
-		Verbose:          a.config.Verbose,
-		Debug:            a.config.Debug,
-		Hooks:            hooks,
-		ExtensionServers: api.New(ctx, a),
-		ExtensionsSchema: database.SchemaExtensions,
+		Version:                 string(apiv1.K8sdAPIVersion),
+		Verbose:                 a.config.Verbose,
+		Debug:                   a.config.Debug,
+		Hooks:                   hooks,
+		ExtensionServers:        api.New(ctx, a, a.config.DrainConnectionsTimeout),
+		ExtensionsSchema:        database.SchemaExtensions,
+		DrainConnectionsTimeout: a.config.DrainConnectionsTimeout,
 	})
 	if err != nil {
 		return fmt.Errorf("failed to run microcluster: %w", err)