SetMaxOpenConns > zookeepers

[JohnCoene]

I'm running into an issue when I set SetMaxOpenConns to something greater than the number of zookeeper nodes available.

I'm not confident whether it is a bug or intentional, though my understanding was that I could create multiple connections to single cluster.

I believe the error occurs here because eindex is out of range.

go-drill/client.go

Line 173 in eb99719

return newClient, newClient.ConnectEndpoint(ctx, zook.GetEndpoint(newClient.drillBits[eindex]))

Example

package main

import (
	"database/sql"
	"fmt"
	"log"
	"strings"
	"sync"

	_ "github.com/factset/go-drill/driver"
)

type AWS struct {
	key    string
	secret string
}

var maxConnections int = 6

func ConnectDrill() (*sql.DB, error) {
	props := []string{
		"zk=localhost:2181,localhost:2182,localhost:2183",
		"cluster=drillbits1",
		"schema=s3",
	}

	db, err := sql.Open("drill", strings.Join(props, ";"))
	if err != nil {
		return nil, err
	}
	if err = db.Ping(); err != nil {
		return nil, err
	}

	db.SetMaxOpenConns(maxConnections)

	return db, nil
}

func query(con *sql.DB, wg *sync.WaitGroup) {
	defer wg.Done()
	rows, err := con.Query("SELECT * FROM sys.drillbits")

	if err != nil {
		log.Panic(err)
	}

	for rows.Next() {
		rows.Scan()
	}
	fmt.Println("queried")
}

func main() {
	var wg sync.WaitGroup

	con, _ := ConnectDrill()

	wg.Add(10)
	go query(con, &wg)
	go query(con, &wg)
	go query(con, &wg)
	go query(con, &wg)
	go query(con, &wg)
	go query(con, &wg)
	go query(con, &wg)
	go query(con, &wg)
	go query(con, &wg)
	go query(con, &wg)

	wg.Wait()
}

oroutine 75 [running]:
github.com/factset/go-drill.(*Client).NewConnection(0xc0000f1500, {0xa9c7f0, 0xc000024110})
	/home/john/go/pkg/mod/github.com/factset/go-drill@v1.2.0/client.go:173 +0x475
github.com/JohnCoene/go-drill/driver.(*connector).Connect(0x0?, {0xa9c7f0?, 0xc000024110?})
	/home/john/Golang/src/github.com/JohnCoene/go-drill/driver/connector.go:19 +0x2f
database/sql.(*DB).conn(0xc00020cd00, {0xa9c7f0, 0xc000024110}, 0x1)
	/usr/local/go/src/database/sql/sql.go:1395 +0x782
database/sql.(*DB).query(0x0?, {0xa9c7f0, 0xc000024110}, {0x9c8f44, 0x1b}, {0x0, 0x0, 0x0}, 0x0?)
	/usr/local/go/src/database/sql/sql.go:1732 +0x5d
database/sql.(*DB).QueryContext(0x0?, {0xa9c7f0, 0xc000024110}, {0x9c8f44, 0x1b}, {0x0, 0x0, 0x0})
	/usr/local/go/src/database/sql/sql.go:1710 +0xda
database/sql.(*DB).Query(...)
	/usr/local/go/src/database/sql/sql.go:1728
main.query(0x0?, 0x0?)
	/home/john/Golang/src/github.com/JohnCoene/go-drill/cmd/main.go:42 +0x8c
created by main.main
	/home/john/Golang/src/github.com/JohnCoene/go-drill/cmd/main.go:66 +0x299
exit status 2

shell returned 1

And thanks for making this package!