Adding config option to limit connections to the db

cmd/web/config.toml

@@ -70,10 +70,17 @@
 
   [server.backend]
     # Drivers: https://github.com/golang/go/wiki/SQLDrivers
-    # Postgres: https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNSTRING
     driver = "postgres"
+
+    # Postgres: https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNSTRING
     url = "postgresql://postgres@localhost:15432/eri?sslmode=disable"
 
+    # Maximum connections allowed to the backend
+    maxConnections = 10
+
+    # Maximum idle connections (must be less than maxConnections). 0 Means no idle connections are retained.
+    maxIdleConnections = 2
+
   [server.graphql]
 
     prettyOutput = true

cmd/web/config/config.go

@@ -72,8 +72,10 @@ type Config struct {
 			Prefix string `toml:"prefix"`
 		} `toml:"profiler"`
 		Backend struct {
-			Driver string `toml:"driver"`
-			URL    string `toml:"url"`
+			Driver             string `toml:"driver"`
+			URL                string `toml:"url"`
+			MaxConnections     uint   `toml:"maxConnections"`
+			MaxIdleConnections uint   `toml:"maxIdleConnections"`
 		} `toml:"backend"`
 		GraphQL struct {
 			PrettyOutput bool `toml:"prettyOutput" flag:"pretty" env:"PRETTY"`

cmd/web/erihttp/server.go

@@ -3,13 +3,16 @@ package erihttp
 import (
 	"io"
 	"log"
+	"net"
 	"net/http"
 	"time"
 
 	"github.com/Dynom/ERI/cmd/web/config"
+	"github.com/sirupsen/logrus"
+	"golang.org/x/net/netutil"
 )
 
-func BuildHTTPServer(mux http.Handler, config config.Config, logWriter io.Writer, handlers ...func(h http.Handler) http.Handler) *http.Server {
+func BuildHTTPServer(mux http.Handler, config config.Config, logger logrus.FieldLogger, logWriter io.Writer, handlers ...func(h http.Handler) http.Handler) *Server {
 	for _, h := range handlers {
 		mux = h(mux)
 	}
@@ -30,5 +33,34 @@ func BuildHTTPServer(mux http.Handler, config config.Config, logWriter io.Writer
 		ErrorLog:          log.New(logWriter, "", 0),
 	}
 
-	return server
+	listener, err := net.Listen("tcp", config.Server.ListenOn)
+	if err != nil {
+		logger.WithFields(logrus.Fields{
+			"error":     err,
+			"listen_on": config.Server.ListenOn,
+		}).Error("Unable to start listener")
+	}
+
+	if config.Server.ConnectionLimit > 0 {
+		listener = netutil.LimitListener(listener, int(config.Server.ConnectionLimit))
+	}
+
+	server.RegisterOnShutdown(func() {
+		err := listener.Close()
+		logger.WithError(err).Debug("Closing listener")
+	})
+
+	return &Server{
+		server:   server,
+		listener: listener,
+	}
+}
+
+type Server struct {
+	server   *http.Server
+	listener net.Listener
+}
+
+func (s *Server) ServeERI() error {
+	return s.server.Serve(s.listener)
 }

cmd/web/erihttp/server_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 
 	"github.com/Dynom/ERI/cmd/web/config"
+	"github.com/sirupsen/logrus/hooks/test"
 )
 
 func TestBuildHTTPServer(t *testing.T) {
@@ -26,7 +27,9 @@ func TestBuildHTTPServer(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			logWriter := &bytes.Buffer{}
-			got := BuildHTTPServer(tt.args.mux, tt.args.config, logWriter, tt.args.handlers...)
+			l, _ := test.NewNullLogger()
+
+			got := BuildHTTPServer(tt.args.mux, tt.args.config, l, logWriter, tt.args.handlers...)
 			if gotLogWriter := logWriter.String(); gotLogWriter != tt.wantLogWriter {
 				t.Errorf("BuildHTTPServer() gotLogWriter = %v, want %v", gotLogWriter, tt.wantLogWriter)
 			}

cmd/web/main.go

@@ -2,15 +2,13 @@ package main
 
 import (
 	"io"
-	"net"
 	"net/http"
 	"os"
 	"time"
 
 	"github.com/Dynom/ERI/cmd/web/pubsub/gcp"
 	"github.com/Dynom/ERI/runtimer"
 	"github.com/rs/cors"
-	"golang.org/x/net/netutil"
 
 	"github.com/Pimmr/rig"
 
@@ -148,7 +146,7 @@ func main() {
 		AllowedHeaders: conf.Server.CORS.AllowedHeaders,
 	})
 
-	s := erihttp.BuildHTTPServer(mux, conf, logWriter,
+	s := erihttp.BuildHTTPServer(mux, conf, logger, logWriter,
 		handlers.WithPathStrip(logger, conf.Server.PathStrip),
 		handlers.NewRateLimitHandler(logger, bucket, conf.Server.RateLimiter.ParkedTTL.AsDuration()),
 		handlers.WithRequestLogger(logger),
@@ -161,19 +159,6 @@ func main() {
 		"listen_on": conf.Server.ListenOn,
 	}).Info("Done, serving requests")
 
-	listener, err := net.Listen("tcp", conf.Server.ListenOn)
-	if err != nil {
-		logger.WithFields(logrus.Fields{
-			"error":     err,
-			"listen_on": conf.Server.ListenOn,
-		}).Error("Unable to start listener")
-	}
-	defer listener.Close()
-
-	if conf.Server.ConnectionLimit > 0 {
-		listener = netutil.LimitListener(listener, int(conf.Server.ConnectionLimit))
-	}
-
-	err = s.Serve(listener)
+	err = s.ServeERI()
 	logger.Errorf("HTTP server stopped %s", err)
 }

cmd/web/util.go

@@ -196,6 +196,9 @@ func createPGPersister(conf config.Config, logger logrus.FieldLogger, hitList *h
 		return nil, nil, err
 	}
 
+	sqlConn.SetMaxOpenConns(int(conf.Server.Backend.MaxConnections))
+	sqlConn.SetMaxIdleConns(int(conf.Server.Backend.MaxIdleConnections))
+
 	err = sqlConn.Ping()
 	if err != nil {
 		return nil, nil, err