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07-leak-kills-mysql.go
57 lines (48 loc) · 1.06 KB
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07-leak-kills-mysql.go
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package main
import (
"database/sql"
_ "github.com/go-sql-driver/mysql"
"log"
)
// This code has a leak and will die after 16,382 executions. Imagine this is
// your long-running API. ~16k executions could take minutes, hours, or days.
// Multiple by N-many servers, and the failure seems to appear randomly without
// a single, unifying cause. The fix is extremely simple.
func main() {
db, err := sql.Open("mysql", "daniel:foo@tcp(localhost:3306)/")
if err != nil {
log.Fatal(err)
}
defer db.Close()
n := 0
for {
if err := doImportantWork(db); err != nil {
log.Fatal("Failed after doing important work only ", n, " times :-(")
}
n++
}
}
func doImportantWork(db *sql.DB) error {
stmt, err := db.Prepare("SELECT 'something important'")
if err != nil {
return err
}
rows, err := stmt.Query()
if err != nil {
return err
}
defer rows.Close()
for rows.Next() {
var something string
err := rows.Scan(&something)
if err != nil {
return err
}
// throw away the result
}
err = rows.Err()
if err != nil {
return err
}
return nil
}