implement host info update hook

main.go

@@ -5,6 +5,7 @@ import (
 	"encoding/xml"
 	"flag"
 	"fmt"
+	"io"
 	"lux/crypto"
 	"lux/host"
 	"lux/node"
@@ -13,6 +14,7 @@ import (
 	"net"
 	"net/netip"
 	"os"
+	"os/exec"
 	"os/signal"
 	"strings"
 	"syscall"
@@ -34,6 +36,12 @@ type LogConfig struct {
 	LogPath string   `xml:",innerxml"`
 }
 
+type UpdateHookConfig struct {
+	XMLName xml.Name `xml:"hook"`
+	HostID  string   `xml:"id"`
+	Script  string   `xml:"script"`
+}
+
 type NodeConfig struct {
 	XMLName   xml.Name `xml:"node"`
 	KeyStore  string   `xml:"keystore"`
@@ -53,6 +61,8 @@ type NodeConfig struct {
 	DNS []string `xml:"dns"`
 
 	Log LogConfig `xml:"log"`
+
+	Hooks []UpdateHookConfig `xml:"hook"`
 }
 
 func setupLogging(log LogConfig) {
@@ -124,6 +134,40 @@ func bootstrapNode() {
 
 var log = logging.MustGetLogger("main")
 
+type hookUpdateSubscriber struct {
+	Hooks map[proto.LuxID]UpdateHookConfig
+}
+
+func (subscriber *hookUpdateSubscriber) HandleStateUpdate(state node.LuxHostState) {
+	hook, ok := subscriber.Hooks[state.HostId]
+	if !ok {
+		return
+	}
+
+	// spawn executable and pipe xml host state into it's stdin
+	xmlBytes, err := xml.Marshal(&rpc.LuxRpcHost{
+		HostID:   state.HostId.String(),
+		Hostname: state.State.Hostname,
+		State:    state.State.IntoRpc(),
+	})
+	if err != nil {
+		log.Errorf("failed to marshal host update for hook: %v\n", err)
+		return
+	}
+
+	buffer := bytes.Buffer{}
+	buffer.Write(xmlBytes)
+
+	cmd := exec.Command(hook.Script)
+	cmd.Stdin = &buffer
+	cmd.Stdout = io.Discard
+	cmd.Stderr = io.Discard
+
+	if err := cmd.Run(); err != nil {
+		log.Warningf("failed to execute script %s: %v\n", hook.Script, err)
+	}
+}
+
 func nodeMain() {
 	xmlBytes, err := os.ReadFile(configPath)
 	if err != nil {
@@ -234,6 +278,21 @@ func nodeMain() {
 		}
 	}
 
+	// add update hooks
+	hook := hookUpdateSubscriber{
+		Hooks: make(map[proto.LuxID]UpdateHookConfig),
+	}
+	for _, item := range config.Hooks {
+		id, err := proto.ParseLuxID(item.HostID)
+		if err != nil {
+			log.Criticalf("failed to parse hook host id %s: %v\n", item.HostID, err)
+			os.Exit(1)
+		}
+
+		hook.Hooks[id] = item
+	}
+	node.AddSubscriber(&hook)
+
 	// start node
 	node.Start()