SMQ-2801 - Add health check endpoint for CoAP adapter (#3022)

Signed-off-by: Felix Gateru <felix.gateru@gmail.com>

coap/api/transport.go

@@ -4,7 +4,9 @@
 package api
 
 import (
+	"bytes"
 	"context"
+	"encoding/json"
 	"fmt"
 	"io"
 	"log/slog"
@@ -72,6 +74,17 @@ func (h *CoAPHandler) ServeCOAP(w mux.ResponseWriter, m *mux.Message) {
 	}
 	defer h.sendResp(w, resp)
 
+	path, err := m.Path()
+	if err != nil {
+		h.logger.Warn(fmt.Sprintf("Error reading path: %s", err))
+		resp.SetCode(codes.BadRequest)
+		return
+	}
+	if strings.TrimPrefix(path, "/") == messaging.HealthTopicPrefix {
+		h.handleHealthCheck(w, m)
+		return
+	}
+
 	msg, err := h.decodeMessage(m)
 	if err != nil {
 		h.logger.Warn(fmt.Sprintf("Error decoding message: %s", err))
@@ -174,6 +187,25 @@ func (h *CoAPHandler) sendResp(w mux.ResponseWriter, resp *pool.Message) {
 	}
 }
 
+func (h *CoAPHandler) handleHealthCheck(w mux.ResponseWriter, m *mux.Message) {
+	pd := messaging.HealthInfo{
+		Status:    messaging.StatusOK,
+		Protocol:  protocol,
+		Timestamp: time.Now().UTC(),
+	}
+	pdBytes, err := json.Marshal(pd)
+	if err != nil {
+		h.logger.Warn(fmt.Sprintf("Error marshaling health info: %s", err))
+	}
+	resp := w.Conn().AcquireMessage(m.Context())
+	defer w.Conn().ReleaseMessage(resp)
+	resp.SetCode(codes.Content)
+	resp.SetToken(m.Token())
+	resp.SetContentFormat(message.AppJSON)
+	resp.SetBody(bytes.NewReader(pdBytes))
+	h.sendResp(w, resp)
+}
+
 func parseKey(msg *mux.Message) (string, error) {
 	authKey, err := msg.Options().GetString(message.URIQuery)
 	if err != nil {

pkg/messaging/health.go

@@ -0,0 +1,22 @@
+// Copyright (c) Abstract Machines
+// SPDX-License-Identifier: Apache-2.0
+
+package messaging
+
+import "time"
+
+const (
+	HealthTopicPrefix = "hc"
+	StatusOK          = "ok"
+)
+
+type HealthInfo struct {
+	// Status contains adapter status.
+	Status string `json:"status"`
+
+	// Protocol contains the protocol used.
+	Protocol string `json:"protocol"`
+
+	// Timestamp of health check.
+	Timestamp time.Time `json:"timestamp"`
+}