Merge pull request #80 from victor-perov/victor-perov/return-error-of…

…-failed-connection

Return original error when connection to ClickHouse failed

conn_go18.go

@@ -14,9 +14,9 @@ import (
 // Ping implements the driver.Pinger
 func (c *conn) Ping(ctx context.Context) error {
 	if c.transport == nil {
-		return driver.ErrBadConn
+		return ErrTransportNil
 	}
-	// make request with empty body, response should be "Ok"
+	// make request with empty body, response must be "Ok"
 	u := &url.URL{Scheme: c.url.Scheme, User: c.url.User, Host: c.url.Host, Path: "/"}
 	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
 	if err != nil {
@@ -27,11 +27,14 @@ func (c *conn) Ping(ctx context.Context) error {
 		c.cancel = nil
 	}()
 	if err != nil {
-		return driver.ErrBadConn
+		return err
 	}
 	resp, err := ioutil.ReadAll(respBody)
-	if err != nil || len(resp) != 4 || !strings.HasPrefix(string(resp), "Ok.") {
-		return driver.ErrBadConn
+	if err != nil {
+		return err
+	}
+	if len(resp) != 4 || !strings.HasPrefix(string(resp), "Ok.") {
+		return ErrIncorrectResponse
 	}
 	return nil
 }

errors.go

@@ -9,11 +9,13 @@ import (
 
 // Various errors the driver might return. Can change between driver versions.
 var (
-	ErrPlaceholderCount = errors.New("clickhouse: wrong placeholder count")
-	ErrNameParams       = errors.New("clickhouse: driver does not support the use of Named Parameters")
-	ErrMalformed        = errors.New("clickhouse: response is malformed")
-	ErrNoLastInsertID   = errors.New("no LastInsertId available")
-	ErrNoRowsAffected   = errors.New("no RowsAffected available")
+	ErrPlaceholderCount  = errors.New("clickhouse: wrong placeholder count")
+	ErrNameParams        = errors.New("clickhouse: driver does not support the use of Named Parameters")
+	ErrMalformed         = errors.New("clickhouse: response is malformed")
+	ErrTransportNil      = errors.New("clickhouse: transport must be set")
+	ErrIncorrectResponse = errors.New("clickhouse: response must contain 'Ok.'")
+	ErrNoLastInsertID    = errors.New("no LastInsertId available")
+	ErrNoRowsAffected    = errors.New("no RowsAffected available")
 )
 
 var errorRe = regexp.MustCompile(`(?s)Code: (\d+),.+DB::Exception: (.+),.*`)