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postgresqlでのconnection timeout

Posted at

症状

pgpool-IIをネットワークインターフェースごと落とした際に、connect_timeoutを設定していても
初回のクエリ実行でのみtimeoutがエラーが返ってこないという現象にあたったのでそれの対処方法
https://godoc.org/github.com/lib/pq

症状が出た時の環境

  • golang: 1.7系
  • ドライバ: lib/pq
  • pgpool-II: 3.6.1
  • PostgreSQL: 9.5

対処方法

golangを1.8にバージョンアップしてQueryRowContextを使う
https://golang.org/pkg/database/sql/#DB.QueryRowContext

QueryRow以外にもContext版があるのでそちらを使う

//前の処理
//Timeout Contextを作成
ctx, cancel := context.WithTimeout(context.Background(), time.Second)
defer cancel()

errChan := make(chan error, 1)

query := "select name from user limit 1"
var name string

go func() {
 errChan <- db.QueryRowContext(ctx, query).Scan(&name)
}()

select {
case <-ctx.Done():
	err = ctx.Err()
	break
case err = <-errChan:
	break
}
//続きの処理
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