[#91] Update values for health metric

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

CHANGELOG.md

@@ -29,6 +29,7 @@ This document outlines major changes between releases.
 - Limit number of objects to delete at one time (TrueCloudLab#37)
 - CompleteMultipartUpload handler now sends whitespace characters to keep alive client's connection (#60)
 - Support new system attributes (#64)
+- Changed values for `frostfs_s3_gw_state_health` metric (#91)
 
 ## [0.26.0] - 2022-12-28
 

cmd/s3-gw/app.go

@@ -182,6 +182,7 @@ func (a *App) initAPI(ctx context.Context) {
 
 func (a *App) initMetrics() {
 	a.metrics = metrics.NewAppMetrics(a.log, frostfs.NewPoolStatistic(a.pool), a.cfg.GetBool(cfgPrometheusEnabled))
+	a.metrics.SetHealth(metrics.HealthStatusStarting)
 }
 
 func (a *App) initResolver() {
@@ -369,7 +370,7 @@ func (a *App) Wait() {
 }
 
 func (a *App) setHealthStatus() {
-	a.metrics.SetHealth(1)
+	a.metrics.SetHealth(metrics.HealthStatusReady)
 }
 
 // Serve runs HTTP server to handle S3 API requests.

metrics/app.go

@@ -37,7 +37,7 @@ func (m *AppMetrics) SetEnabled(enabled bool) {
 	m.mu.Unlock()
 }
 
-func (m *AppMetrics) SetHealth(status int32) {
+func (m *AppMetrics) SetHealth(status HealthStatus) {
 	if !m.isEnabled() {
 		return
 	}
@@ -48,7 +48,7 @@ func (m *AppMetrics) SetHealth(status int32) {
 func (m *AppMetrics) Shutdown() {
 	m.mu.Lock()
 	if m.enabled {
-		m.gate.State.SetHealth(0)
+		m.gate.State.SetHealth(HealthStatusShuttingDown)
 		m.enabled = false
 	}
 	m.gate.Unregister()

metrics/state.go

@@ -4,6 +4,16 @@ import "github.com/prometheus/client_golang/prometheus"
 
 const stateSubsystem = "state"
 
+// HealthStatus of the gate application.
+type HealthStatus int32
+
+const (
+	HealthStatusUndefined    HealthStatus = 0
+	HealthStatusStarting     HealthStatus = 1
+	HealthStatusReady        HealthStatus = 2
+	HealthStatusShuttingDown HealthStatus = 3
+)
+
 type stateMetrics struct {
 	healthCheck prometheus.Gauge
 }
@@ -27,6 +37,6 @@ 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))
 }