metakeule · April 12, 2013 07:48 · Apr 12, 2013
diff --git a/limit.sql b/limit.sql
@@ -0,0 +1,2 @@
+-- limit the number of connections, username is allowed to use
+ALTER Role username CONNECTION LIMIT 10;
diff --git a/load.sh b/load.sh
@@ -0,0 +1,2 @@
+#!/bin/bash
+ab -n 2000 -c 200 http://localhost:8080/
diff --git a/main.go b/main.go
@@ -0,0 +1,150 @@
+package main
+
+import (
+	"database/sql"
+	"fmt"
+	"github.com/lib/pq"
+	"net/http"
+	"os"
+	"strings"
+)
+
+var DB *DbWrapper
+var dbLock = make(chan int, 1)
+var httpLock = make(chan int, 1)
+var nSql = 15
+var reqNum = 0
+
+func Connect(url string) (db *DbWrapper) {
+	p, err := pq.ParseURL(url)
+	if err != nil {
+		panic(err.Error())
+	}
+
+	db, err = Open("postgres", p)
+	db.Debug = true
+	if err != nil {
+		panic(err.Error())
+	}
+	return
+}
+
+func handler(w http.ResponseWriter, r *http.Request) {
+	<-httpLock
+	reqNum++
+	numErrs := 0
+	failed := []string{}
+	for i := 0; i < nSql; i++ {
+		res, err := DB.Query(fmt.Sprintf("SELECT '%v'::int", reqNum*100+i))
+		if err != nil {
+			numErrs++
+			s := strings.ToUpper(fmt.Sprintf("Error (Query): %s", err.Error()))
+			failed = append(failed, s)
+			fmt.Println(s)
+			continue
+		}
+		var ii int
+		res.Next()
+		err = res.Scan(&ii)
+		if err != nil {
+			fmt.Printf("Error (Scan): %s\n", err.Error())
+			continue
+		}
+		if reqNum*100+i != ii {
+			fmt.Printf("Error: %v != %v\n", reqNum*100+i, ii)
+		}
+	}
+	fmt.Printf("Num Errors: %v\nFailed: \n%s\n\n", numErrs, strings.Join(failed, "\n"))
+	fmt.Fprintf(w, "Num Errors: %v\nFailed: \n%s\n\n", numErrs, strings.Join(failed, "\n"))
+	httpLock <- 1
+}
+
+func Open(driverName, dataSourceName string) (ø *DbWrapper, ſ error) {
+	ø = &DbWrapper{dataSourceName: dataSourceName, driverName: driverName}
+	dbLock <- 1
+	return
+}
+
+// wraps a *sql.DB in order to do x queries at a time, to prevent
+//    pq: too many connections for role "user"
+// errors
+type DbWrapper struct {
+	dataSourceName string
+	driverName     string
+	db             *sql.DB
+	Debug          bool
+}
+
+func (ø *DbWrapper) Close() (err error) {
+	err = ø.db.Close()
+	if ø.Debug {
+		fmt.Println("disconnect from db")
+	}
+	dbLock <- 1
+	return
+}
+
+func (ø *DbWrapper) connect() (err error) {
+	<-dbLock
+	ø.db, err = sql.Open(ø.driverName, ø.dataSourceName)
+	// you may try this with go 1.1 beta2
+	//ø.db.SetMaxIdleConns(-1)
+	if ø.Debug {
+		fmt.Println("connect to db")
+	}
+	if err != nil {
+		fmt.Printf("can't connect to DB: %s\n", err.Error())
+	}
+	return
+}
+
+func (ø *DbWrapper) Query(query string, args ...interface{}) (rows *sql.Rows, err error) {
+	err = ø.connect()
+
+	if err != nil {
+		dbLock <- 1
+		return
+	}
+
+	if ø.Debug {
+		fmt.Printf("Query: \n------\n%s\n-----\nwith args: %#v\n", query, args)
+	}
+	st, err := ø.db.Prepare(query)
+	defer func() {
+		if st != nil {
+			st.Close()
+		}
+		ø.Close()
+	}()
+	if err != nil {
+		return
+	}
+	rows, err = st.Query(args...)
+	return
+}
+
+/*
+	prepare the postgres server with
+
+		ALTER Role username CONNECTION LIMIT 10;
+
+	run webserver with
+
+		export DB_URL=postgres://user:password@localhost:5432/database ; go run main.go
+
+	run ab with
+
+		ab -n 2000 -c 200 http://localhost:8080/
+
+*/
+func main() {
+	DB = Connect(os.Getenv("DB_URL"))
+	httpLock <- 1
+	http.HandleFunc("/", handler)
+	fmt.Println("serving on localhost:8080")
+
+	err := http.ListenAndServe(":8080", nil)
+	if err != nil {
+		fmt.Printf("Error (Serving): %s\n", err)
+	}
+}
diff --git a/run.sh b/run.sh
@@ -0,0 +1,2 @@
+#!/bin/bash
+export DB_URL=postgres://user:password@localhost:5432/database ; go run main.go
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		-- limit the number of connections, username is allowed to use
		ALTER Role username CONNECTION LIMIT 10;
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		#!/bin/bash
		ab -n 2000 -c 200 http://localhost:8080/
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		#!/bin/bash
		export DB_URL=postgres://user:password@localhost:5432/database ; go run main.go