feat: update health endpoint (#924)

Author: mattjohnsonpint

CHANGELOG.md

@@ -8,6 +8,7 @@ NOTE: all releases may include dependency updates, not specifically mentioned
 
 - feat: integrate try-as library [#912](https://github.com/hypermodeinc/modus/pull/912)
 - fix: check topic actor status before publishing events [#918](https://github.com/hypermodeinc/modus/pull/918)
+- feat: update health endpoint [#924](https://github.com/hypermodeinc/modus/pull/924)
 
 ## 2025-06-25 - Runtime v0.18.2
 

runtime/actors/agents.go

@@ -323,27 +323,3 @@ func ListActiveAgents(ctx context.Context) ([]AgentInfo, error) {
 
 	return results, nil
 }
-
-func ListLocalAgents(ctx context.Context) []AgentInfo {
-	if _actorSystem == nil {
-		return nil
-	}
-
-	span, _ := utils.NewSentrySpanForCurrentFunc(ctx)
-	defer span.Finish()
-
-	actors := _actorSystem.Actors()
-	results := make([]AgentInfo, 0, len(actors))
-
-	for _, pid := range actors {
-		if actor, ok := pid.Actor().(*wasmAgentActor); ok {
-			results = append(results, AgentInfo{
-				Id:     actor.agentId,
-				Name:   actor.agentName,
-				Status: actor.status,
-			})
-		}
-	}
-
-	return results
-}

runtime/app/app.go

@@ -97,11 +97,15 @@ func ModusHomeDir() string {
 }
 
 func KubernetesNamespace() (string, bool) {
+	return kubernetesNamespace()
+}
+
+var kubernetesNamespace = sync.OnceValues(func() (string, bool) {
 	if ns := os.Getenv("NAMESPACE"); ns != "" {
 		return ns, true
 	}
 	if data, err := os.ReadFile("/var/run/secrets/kubernetes.io/serviceaccount/namespace"); err == nil {
 		return strings.TrimSpace(string(data)), true
 	}
 	return "", false
-}
+})

runtime/httpserver/health.go

@@ -10,43 +10,34 @@
 package httpserver
 
 import (
-	"encoding/json"
-	"fmt"
 	"net/http"
+	"runtime"
 
-	"github.com/hypermodeinc/modus/runtime/actors"
 	"github.com/hypermodeinc/modus/runtime/app"
+	"github.com/hypermodeinc/modus/runtime/logger"
+	"github.com/hypermodeinc/modus/runtime/utils"
 )
 
 var healthHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-	env := app.Config().Environment()
-	ver := app.VersionNumber()
-	agents := actors.ListLocalAgents(r.Context())
 
-	w.Header().Set("Content-Type", "application/json")
-	w.WriteHeader(http.StatusOK)
-
-	// custom format the JSON response for easy readability
-	_, _ = w.Write([]byte(`{
-  "status": "ok",
-  "environment": "` + env + `",
-  "version": "` + ver + `",
-`))
-
-	if len(agents) == 0 {
-		_, _ = w.Write([]byte(`  "agents": []` + "\n"))
-	} else {
-		_, _ = w.Write([]byte(`  "agents": [` + "\n"))
-		for i, agent := range agents {
-			if i > 0 {
-				_, _ = w.Write([]byte(",\n"))
-			}
-			name, _ := json.Marshal(agent.Name)
-			_, _ = w.Write(fmt.Appendf(nil, `    {"id": "%s", "name": %s, "status": "%s"}`, agent.Id, name, agent.Status))
-		}
-		_, _ = w.Write([]byte("\n  ]\n"))
+	data := []utils.KeyValuePair{
+		{Key: "status", Value: "ok"},
+		{Key: "environment", Value: app.Config().Environment()},
+		{Key: "app_version", Value: app.VersionNumber()},
+		{Key: "go_version", Value: runtime.Version()},
+	}
+	if ns, ok := app.KubernetesNamespace(); ok {
+		data = append(data, utils.KeyValuePair{Key: "kubernetes_namespace", Value: ns})
 	}
 
-	_, _ = w.Write([]byte("}\n"))
+	jsonBytes, err := utils.MakeJsonObject(data, true)
+	if err != nil {
+		logger.Err(r.Context(), err).Msg("Failed to serialize health check response.")
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
 
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusOK)
+	_, _ = w.Write(jsonBytes)
 })

runtime/utils/json.go

@@ -31,3 +31,59 @@ func JsonDeserialize(data []byte, v any) error {
 	dec.UseNumber()
 	return dec.Decode(v)
 }
+
+type KeyValuePair struct {
+	Key   string
+	Value any
+}
+
+// MakeJsonObject creates a JSON object from the given key-value pairs.
+func MakeJsonObject(pairs []KeyValuePair, pretty bool) ([]byte, error) {
+	var buf bytes.Buffer
+
+	if pretty {
+		buf.WriteString("{\n")
+		for i, kv := range pairs {
+			keyBytes, err := json.Marshal(kv.Key)
+			if err != nil {
+				return nil, err
+			}
+			valBytes, err := json.Marshal(kv.Value)
+			if err != nil {
+				return nil, err
+			}
+
+			buf.WriteString("  ")
+			buf.Write(keyBytes)
+			buf.WriteString(": ")
+			buf.Write(valBytes)
+			if i < len(pairs)-1 {
+				buf.WriteByte(',')
+			}
+			buf.WriteByte('\n')
+		}
+		buf.WriteString("}\n")
+	} else {
+		buf.WriteByte('{')
+		for i, kv := range pairs {
+			keyBytes, err := json.Marshal(kv.Key)
+			if err != nil {
+				return nil, err
+			}
+			valBytes, err := json.Marshal(kv.Value)
+			if err != nil {
+				return nil, err
+			}
+
+			buf.Write(keyBytes)
+			buf.WriteByte(':')
+			buf.Write(valBytes)
+			if i < len(pairs)-1 {
+				buf.WriteByte(',')
+			}
+		}
+		buf.WriteByte('}')
+	}
+
+	return buf.Bytes(), nil
+}