add healthcheck service

internal/api/http/handlerbuilder.go

@@ -5,6 +5,7 @@ import (
 	"net/http"
 	"net/http/pprof"
 
+	"git.loyso.art/frx/devsim/internal/probe"
 	"git.loyso.art/frx/devsim/internal/store"
 )
 
@@ -36,6 +37,11 @@ func (s *handlersBuilder) MountProfileHandlers() {
 	s.mux.HandleFunc("/debug/pprof/trace", pprof.Trace)
 }
 
+func (s *handlersBuilder) MountProbeHandlers(r probe.Reporter) {
+	s.mux.HandleFunc("/health", livenessHandler(r))
+	s.mux.HandleFunc("/ready", readinessHandler(r))
+}
+
 func (s *handlersBuilder) Build() http.Handler {
 	return s.mux
 }

internal/api/http/healthhandlers.go

@@ -0,0 +1,55 @@
+package http
+
+import (
+	"net/http"
+
+	"git.loyso.art/frx/devsim/internal/probe"
+)
+
+// ListenAndServe runs server to accept incoming connections. This function blocks on
+// handling connections.
+func livenessHandler(reporter probe.Reporter) http.HandlerFunc {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodGet {
+			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+			return
+		}
+
+		switch reporter.ReportLiveness() {
+		case probe.LivenessOk:
+			w.WriteHeader(http.StatusOK)
+		case probe.LivenessTimeout:
+			w.WriteHeader(http.StatusInternalServerError)
+		case probe.LivenessUnknown:
+			w.WriteHeader(http.StatusOK)
+		}
+	})
+}
+
+func readinessHandler(reporter probe.Reporter) http.HandlerFunc {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodGet {
+			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+			return
+		}
+
+		var status string
+		var code int
+		switch reporter.ReportReadiness() {
+		case probe.ReadinessOk:
+			status = "ok"
+			code = http.StatusOK
+		case probe.ReadinessFailed:
+			status = "failed"
+			code = http.StatusInternalServerError
+		case probe.ReadinessNotReady:
+			status = "not-ready"
+			code = http.StatusOK
+		case probe.ReadinessUnknown:
+			status = "unknown"
+			code = http.StatusOK
+		}
+		w.Header().Set("X-Readiness-Status", status)
+		w.WriteHeader(code)
+	})
+}