dbsqlconnfail: pq or database/sql ErrBadConn unhealthy connection reuse

Readme.md

$ go install
$ dbsqlconnfail

In another window:

$ curl localhost:8080/1
OK
$ # kill postgres, let it restart
$ curl localhost:8080/1
FAIL

Restart postgres + dbsqlconnfail, then:

$ curl localhost:8080/2
OK
$ # kill postgres, let it restart
$ curl localhost:8080/2
OK

main.go

package main

import (
	"database/sql"
	"fmt"
	"github.com/bmizerany/pq"
	"net/http"
)

func main() {
	opendb("postgres://bgentry:@localhost:5432/maestro")
	http.HandleFunc("/1", func(w http.ResponseWriter, r *http.Request) {
		response(w, TestDbConnection1())
	})
	http.HandleFunc("/2", func (w http.ResponseWriter, r *http.Request) {
		response(w, TestDbConnection2())
	})
	switch {
		case !TestDbConnection1(): panic("failed test 1")
		case !TestDbConnection2(): panic("failed test 2")
	}
	http.ListenAndServe(":8080", nil)
}

var pg *sql.DB

func opendb(databaseURL string) {
	cs, err := pq.ParseURL(databaseURL)
	if err != nil {
		fmt.Printf("fatal database_url_parse_error error=%v\n", err.Error())
	}

	cs += " sslmode=disable"

	pg, err = sql.Open("postgres", cs)
	if err != nil {
		fmt.Printf("fatal database_connection_error error=%v\n", err.Error())
	}
}

func response(w http.ResponseWriter, result bool) {
	if result {
		w.Write([]byte("OK\n"))
	} else {
		w.WriteHeader(500)
		w.Write([]byte("FAIL\n"))
	}
}

func TestDbConnection1() bool {
	var r int
	err := pg.QueryRow("SELECT 1").Scan(&r)
	return handleConnTest(r, err)
}

func TestDbConnection2() bool {
	var r int
	rows, err := pg.Query("SELECT 1")
	if err != nil {
		fmt.Printf("Error during test query: %v\n", err)
		return false
	}
	rows.Next()
	err = rows.Scan(&r)
	if err != nil {
		fmt.Printf("Error during test scan: %v\n", err)
		return false
	}
	return handleConnTest(r, err)
}

func handleConnTest(r int, err error) bool {
	switch {
	case err != nil:
		fmt.Printf("error db_connection_test_failure error=%v\n", err.Error())
		return false
	case r != 1:
		fmt.Printf("error db_connection_test_failure error=%v\n", fmt.Sprintf("query returned %v", r))
		return false
	}
	return true
}