Setup basic prom metrics endpoint (#624)

* Setup basic prom metrics endpoint
* Use default prom handler to expose go runtime metrics

pkg/api/api.go

@@ -16,6 +16,7 @@ import (
 	"github.com/sosedoff/pgweb/pkg/client"
 	"github.com/sosedoff/pgweb/pkg/command"
 	"github.com/sosedoff/pgweb/pkg/connection"
+	"github.com/sosedoff/pgweb/pkg/metrics"
 	"github.com/sosedoff/pgweb/pkg/shared"
 	"github.com/sosedoff/pgweb/static"
 )
@@ -278,6 +279,12 @@ func Disconnect(c *gin.Context) {
 		return
 	}
 
+	if command.Opts.Sessions {
+		result := DbSessions.Remove(getSessionId(c.Request))
+		successResponse(c, gin.H{"success": result})
+		return
+	}
+
 	conn := DB(c)
 	if conn == nil {
 		badRequest(c, errNotConnected)
@@ -492,6 +499,8 @@ func GetTableConstraints(c *gin.Context) {
 
 // HandleQuery runs the database query
 func HandleQuery(query string, c *gin.Context) {
+	metrics.IncrementQueriesCount()
+
 	rawQuery, err := base64.StdEncoding.DecodeString(desanitize64(query))
 	if err == nil {
 		query = string(rawQuery)

pkg/api/routes.go

@@ -4,6 +4,7 @@ import (
 	"github.com/gin-gonic/gin"
 
 	"github.com/sosedoff/pgweb/pkg/command"
+	"github.com/sosedoff/pgweb/pkg/metrics"
 )
 
 func SetupMiddlewares(group *gin.RouterGroup) {
@@ -53,3 +54,9 @@ func SetupRoutes(router *gin.Engine) {
 	api.GET("/bookmarks", GetBookmarks)
 	api.GET("/export", DataExport)
 }
+
+func SetupMetrics(engine *gin.Engine) {
+	if command.Opts.MetricsEnabled && command.Opts.MetricsAddr == "" {
+		engine.GET("/metrics", gin.WrapH(metrics.Handler()))
+	}
+}

pkg/api/session_manager.go

@@ -7,6 +7,7 @@ import (
 	"github.com/sirupsen/logrus"
 
 	"github.com/sosedoff/pgweb/pkg/client"
+	"github.com/sosedoff/pgweb/pkg/metrics"
 )
 
 type SessionManager struct {
@@ -58,8 +59,10 @@ func (m *SessionManager) Get(id string) *client.Client {
 
 func (m *SessionManager) Add(id string, conn *client.Client) {
 	m.mu.Lock()
+	defer m.mu.Unlock()
+
 	m.sessions[id] = conn
-	m.mu.Unlock()
+	metrics.SetSessionsCount(len(m.sessions))
 }
 
 func (m *SessionManager) Remove(id string) bool {
@@ -72,6 +75,7 @@ func (m *SessionManager) Remove(id string) bool {
 		delete(m.sessions, id)
 	}
 
+	metrics.SetSessionsCount(len(m.sessions))
 	return ok
 }