[#32] Update health metric values

Now values are:
0 - undefined
1 - starting
2 - ready
3 - shutting down

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>

CHANGELOG.md

@@ -14,6 +14,7 @@ This document outlines major changes between releases.
 - Errors have become more detailed (#18)
 - Update system attribute names (#22)
 - Separate integration tests with build tags (#24)
+- Changed values for `frostfs_http_gw_state_health` metric (#32)
 
 ### Updating from v0.26.0
 

app.go

@@ -62,15 +62,10 @@ type (
 
 	gateMetrics struct {
 		logger   *zap.Logger
-		provider GateMetricsProvider
+		provider *metrics.GateMetrics
 		mu       sync.RWMutex
 		enabled  bool
 	}
-
-	GateMetricsProvider interface {
-		SetHealth(int32)
-		Unregister()
-	}
 )
 
 // WithLogger returns Option to set a specific logger.
@@ -214,9 +209,10 @@ func (a *app) getResolverConfig() ([]string, *resolver.Config) {
 func (a *app) initMetrics() {
 	gateMetricsProvider := metrics.NewGateMetrics(a.pool)
 	a.metrics = newGateMetrics(a.log, gateMetricsProvider, a.cfg.GetBool(cfgPrometheusEnabled))
+	a.metrics.SetHealth(metrics.HealthStatusStarting)
 }
 
-func newGateMetrics(logger *zap.Logger, provider GateMetricsProvider, enabled bool) *gateMetrics {
+func newGateMetrics(logger *zap.Logger, provider *metrics.GateMetrics, enabled bool) *gateMetrics {
 	if !enabled {
 		logger.Warn("metrics are disabled")
 	}
@@ -236,7 +232,7 @@ func (m *gateMetrics) SetEnabled(enabled bool) {
 	m.mu.Unlock()
 }
 
-func (m *gateMetrics) SetHealth(status int32) {
+func (m *gateMetrics) SetHealth(status metrics.HealthStatus) {
 	m.mu.RLock()
 	if !m.enabled {
 		m.mu.RUnlock()
@@ -250,7 +246,7 @@ func (m *gateMetrics) SetHealth(status int32) {
 func (m *gateMetrics) Shutdown() {
 	m.mu.Lock()
 	if m.enabled {
-		m.provider.SetHealth(0)
+		m.provider.SetHealth(metrics.HealthStatusShuttingDown)
 		m.enabled = false
 	}
 	m.provider.Unregister()
@@ -335,7 +331,7 @@ func (a *app) Wait() {
 }
 
 func (a *app) setHealthStatus() {
-	a.metrics.SetHealth(1)
+	a.metrics.SetHealth(metrics.HealthStatusReady)
 }
 
 func (a *app) Serve(ctx context.Context) {

metrics/metrics.go

@@ -31,6 +31,16 @@ const (
 	methodCreateSession    = "create_session"
 )
 
+// HealthStatus of the gate application.
+type HealthStatus int32
+
+const (
+	HealthStatusUndefined    HealthStatus = 0
+	HealthStatusStarting     HealthStatus = 1
+	HealthStatusReady        HealthStatus = 2
+	HealthStatusShuttingDown HealthStatus = 3
+)
+
 type GateMetrics struct {
 	stateMetrics
 	poolMetricsCollector
@@ -87,7 +97,7 @@ func (m stateMetrics) unregister() {
 	prometheus.Unregister(m.healthCheck)
 }
 
-func (m stateMetrics) SetHealth(s int32) {
+func (m stateMetrics) SetHealth(s HealthStatus) {
 	m.healthCheck.Set(float64(s))
 }