Adjust the amount of concurrent postgres connections

And respect cgroups when setting GOMAXPROCS

cmd/image-service/main.go

@@ -22,6 +22,7 @@ import (
 	api "github.com/DMarby/picsum-photos/internal/imageapi"
 
 	"github.com/jamiealquiza/envy"
+	"go.uber.org/automaxprocs/maxprocs"
 	"go.uber.org/zap"
 )
 
@@ -68,6 +69,9 @@ func main() {
 	log := logger.New(*loglevel)
 	defer log.Sync()
 
+	// Set GOMAXPROCS
+	maxprocs.Set(maxprocs.Logger(log.Infof))
+
 	// Set up context for shutting down
 	shutdownCtx, shutdown := context.WithCancel(context.Background())
 	defer shutdown()

cmd/picsum-photos/main.go

@@ -18,6 +18,7 @@ import (
 	"github.com/DMarby/picsum-photos/internal/logger"
 
 	"github.com/jamiealquiza/envy"
+	"go.uber.org/automaxprocs/maxprocs"
 	"go.uber.org/zap"
 )
 
@@ -42,7 +43,8 @@ var (
 	databaseFilePath = flag.String("database-file-path", "./test/fixtures/file/metadata.json", "path to the database file")
 
 	// Database - Postgresql
-	databasePostgresqlAddress = flag.String("database-postgresql-address", "postgresql://postgres@127.0.0.1/postgres", "postgresql address")
+	databasePostgresqlAddress  = flag.String("database-postgresql-address", "postgresql://postgres@127.0.0.1/postgres", "postgresql address")
+	databasePostgresqlMaxConns = flag.Int("database-postgresql-max-conns", 0, "postgresql max connections")
 
 	// HMAC
 	hmacKey = flag.String("hmac-key", "", "hmac key to use for authentication between services")
@@ -59,6 +61,9 @@ func main() {
 	log := logger.New(*loglevel)
 	defer log.Sync()
 
+	// Set GOMAXPROCS
+	maxprocs.Set(maxprocs.Logger(log.Infof))
+
 	// Set up context for shutting down
 	shutdownCtx, shutdown := context.WithCancel(context.Background())
 	defer shutdown()
@@ -144,7 +149,7 @@ func setupBackends() (database database.Provider, err error) {
 	case "file":
 		database, err = fileDatabase.New(*databaseFilePath)
 	case "postgresql":
-		database, err = postgresql.New(*databasePostgresqlAddress)
+		database, err = postgresql.New(*databasePostgresqlAddress, *databasePostgresqlMaxConns)
 	default:
 		err = fmt.Errorf("invalid database backend")
 	}

go.mod

@@ -15,6 +15,7 @@ require (
 	github.com/spf13/cobra v1.0.0 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
 	github.com/twmb/murmur3 v1.1.3
+	go.uber.org/automaxprocs v1.3.0
 	go.uber.org/zap v1.15.0
 	golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9 // indirect
 	golang.org/x/lint v0.0.0-20200302205851-738671d3881b // indirect

go.sum

@@ -355,6 +355,8 @@ go.uber.org/atomic v1.3.2/go.mod h1:gD2HeocX3+yG+ygLZcrzQJaqmWj9AIm7n08wl/qW/PE=
 go.uber.org/atomic v1.4.0/go.mod h1:gD2HeocX3+yG+ygLZcrzQJaqmWj9AIm7n08wl/qW/PE=
 go.uber.org/atomic v1.6.0 h1:Ezj3JGmsOnG1MoRWQkPBsKLe9DwWD9QeXzTRzzldNVk=
 go.uber.org/atomic v1.6.0/go.mod h1:sABNBOSYdrvTF6hTgEIbc7YasKWGhgEQZyfxyTvoXHQ=
+go.uber.org/automaxprocs v1.3.0 h1:II28aZoGdaglS5vVNnspf28lnZpXScxtIozx1lAjdb0=
+go.uber.org/automaxprocs v1.3.0/go.mod h1:9CWT6lKIep8U41DDaPiH6eFscnTyjfTANNQNx6LrIcA=
 go.uber.org/multierr v1.1.0/go.mod h1:wR5kodmAFQ0UK8QlbwjlSNy0Z68gJhDJUG5sjR94q/0=
 go.uber.org/multierr v1.5.0 h1:KCa4XfM8CWFCpxXRGok+Q0SS/0XBhMDbHHGABQLvD2A=
 go.uber.org/multierr v1.5.0/go.mod h1:FeouvMocqHpRaaGuG9EjoKcStLC43Zu/fmqdUMPcKYU=

internal/database/postgresql/postgresql.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"database/sql"
 	"fmt"
+	"math"
 	"math/rand"
 	"time"
 
@@ -27,13 +28,17 @@ type Provider struct {
 }
 
 // New establishes the database connection and returns a new Provider instance
-func New(address string) (*Provider, error) {
+func New(address string, maxConns int) (*Provider, error) {
 	// Establish the database connection
 	db, err := sqlx.Open("pgx", address)
 	if err != nil {
 		return nil, err
 	}
 
+	// Limit the maximum open and idle database connections
+	db.SetMaxOpenConns(maxConns)
+	db.SetMaxIdleConns(int(math.Ceil(float64(maxConns) / 2)))
+
 	// Use Unsafe so that the app doesn't fail if we add new columns to the database
 	return &Provider{
 		db: db.Unsafe(),

internal/database/postgresql/postgresql_test.go

@@ -116,7 +116,7 @@ func TestPostgresql(t *testing.T) {
 
 // mustInitialize connects to and migrates the database
 func mustInitialize(t *testing.T, migrationsURL string) *postgresql.Provider {
-	db, err := postgresql.New(address)
+	db, err := postgresql.New(address, 0)
 	if err != nil {
 		t.Fatal(err)
 	}