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 +1,86 @@
+package phase
+
+import (
+	"fmt"
+	"strings"
+	"sync"
+
+	"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
+
+	steps map[*cluster.Host][]string
+}
+
+// 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.steps = make(map[*cluster.Host][]string)
+	for _, h := range config.Spec.Hosts {
+		if len(h.Hooks) > 0 {
+			p.steps[h] = h.Hooks.ForActionAndStage(p.Action, p.Stage)
+		}
+	}
+
+	return nil
+}
+
+// ShouldRun is true when there are hosts that need to be connected
+func (p *RunHooks) ShouldRun() bool {
+	return len(p.steps) > 0
+}
+
+// Run does all the prep work on the hosts in parallel
+func (p *RunHooks) Run() error {
+	var wg sync.WaitGroup
+	var errors []string
+	type erritem struct {
+		host string
+		err  error
+	}
+	ec := make(chan erritem, 1)
+
+	wg.Add(len(p.steps))
+
+	for h, steps := range p.steps {
+		go func(h *cluster.Host, steps []string) {
+			for _, s := range steps {
+				err := h.Exec(s)
+				if err != nil {
+					ec <- erritem{h.String(), err}
+					return // do not exec remaining steps if one fails
+				}
+			}
+
+			ec <- erritem{h.String(), nil}
+		}(h, steps)
+	}
+
+	go func() {
+		for e := range ec {
+			if e.err != nil {
+				errors = append(errors, fmt.Sprintf("%s: %s", e.host, e.err.Error()))
+			}
+			wg.Done()
+		}
+	}()
+
+	wg.Wait()
+
+	if len(errors) > 0 {
+		return fmt.Errorf("failed on %d hosts:\n - %s", len(errors), strings.Join(errors, "\n - "))
+	}
+
+	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:
+            - "date > /before-apply.hook"
+          after:
+            - "date > /after-apply.hook"
     - role: worker
       uploadBinary: true
       os: "$OS_OVERRIDE"