Configurable hooks to run commands on target hosts during operations

cmd/apply.go

@@ -76,6 +76,7 @@ var applyCommand = &cli.Command{
 			&phase.ValidateHosts{},
 			&phase.GatherK0sFacts{},
 			&phase.ValidateFacts{SkipDowngradeCheck: ctx.Bool("disable-downgrade-check")},
+			&phase.RunHooks{Stage: "before", Action: "apply"},
 			&phase.ConfigureK0s{},
 			&phase.Restore{
 				RestoreFrom: ctx.String("restore-from"),
@@ -87,6 +88,7 @@ var applyCommand = &cli.Command{
 			&phase.UpgradeWorkers{
 				NoDrain: ctx.Bool("no-drain"),
 			},
+			&phase.RunHooks{Stage: "after", Action: "apply"},
 			&phase.Disconnect{},
 		)
 

cmd/backup.go

@@ -47,7 +47,9 @@ var backupCommand = &cli.Command{
 			&phase.DetectOS{},
 			&phase.GatherFacts{},
 			&phase.GatherK0sFacts{},
+			&phase.RunHooks{Stage: "before", Action: "backup"},
 			&phase.Backup{},
+			&phase.RunHooks{Stage: "after", Action: "backup"},
 			&phase.Disconnect{},
 		)
 

cmd/reset.go

@@ -70,7 +70,9 @@ var resetCommand = &cli.Command{
 			&phase.DetectOS{},
 			&phase.PrepareHosts{},
 			&phase.GatherK0sFacts{},
+			&phase.RunHooks{Stage: "before", Action: "reset"},
 			&phase.Reset{},
+			&phase.RunHooks{Stage: "after", Action: "reset"},
 			&phase.Disconnect{},
 		)
 

config/cluster/hook.go

@@ -0,0 +1,12 @@
+package cluster
+
+// Hooks define a list of hooks such as hooks["apply"]["before"] = ["ls -al", "rm foo.txt"]
+type Hooks map[string]map[string][]string
+
+// ForActionAndStage return hooks for given action and stage
+func (h Hooks) ForActionAndStage(action, stage string) []string {
+	if len(h[action]) > 0 {
+		return h[action][stage]
+	}
+	return nil
+}

config/cluster/host.go

@@ -28,6 +28,7 @@ type Host struct {
 	InstallFlags     Flags             `yaml:"installFlags,omitempty"`
 	Files            []UploadFile      `yaml:"files,omitempty"`
 	OSIDOverride     string            `yaml:"os,omitempty"`
+	Hooks            Hooks             `yaml:"hooks,omitempty"`
 
 	Metadata   HostMetadata `yaml:"-"`
 	Configurer configurer   `yaml:"-"`

phase/runhooks.go

@@ -0,0 +1,53 @@
+package phase
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/k0sproject/k0sctl/config"
+	"github.com/k0sproject/k0sctl/config/cluster"
+)
+
+var _ phase = &RunHooks{}
+
+// RunHooks phase runs a set of hooks configured for the host
+type RunHooks struct {
+	Action string
+	Stage  string
+	hosts  cluster.Hosts
+}
+
+// Title for the phase
+func (p *RunHooks) Title() string {
+	return fmt.Sprintf("Run %s %s Hooks", strings.Title(p.Stage), strings.Title(p.Action))
+}
+
+// Prepare digs out the hosts with steps from the config
+func (p *RunHooks) Prepare(config *config.Cluster) error {
+	p.hosts = config.Spec.Hosts.Filter(func(h *cluster.Host) bool {
+		return len(h.Hooks.ForActionAndStage(p.Action, p.Stage)) > 0
+	})
+
+	return nil
+}
+
+// ShouldRun is true when there are hosts that need to be connected
+func (p *RunHooks) ShouldRun() bool {
+	return len(p.hosts) > 0
+}
+
+// Run does all the prep work on the hosts in parallel
+func (p *RunHooks) Run() error {
+	return p.hosts.ParallelEach(p.runHooksForHost)
+}
+
+func (p *RunHooks) runHooksForHost(h *cluster.Host) error {
+	steps := h.Hooks.ForActionAndStage(p.Action, p.Stage)
+	for _, s := range steps {
+		err := h.Exec(s)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}

smoke-test/k0sctl.yaml.tpl

@@ -9,6 +9,12 @@ spec:
         address: "127.0.0.1"
         port: 9022
         keyPath: ./id_rsa_k0s
+      hooks:
+        apply:
+          before:
+            - "echo hello > apply.hook"
+          after:
+            - "grep -q hello apply.hook"
     - role: worker
       uploadBinary: true
       os: "$OS_OVERRIDE"

smoke-test/smoke-basic.sh

@@ -13,4 +13,7 @@ envsubst < "${K0SCTL_TEMPLATE}" > k0sctl.yaml
 deleteCluster
 createCluster
 ../k0sctl apply --config k0sctl.yaml --debug
+# Check that the hooks got actually ran properly
+footloose ssh root@manager0 -- grep -q hello apply.hook
+
 ../k0sctl kubeconfig --config k0sctl.yaml | grep -v -- "-data"