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Check connection liveness in beginTx
This commit fixes for ClickHouse#213. If the connection closes from the server side for some reason, the database driver returns driver.ErrBadConn to database/sql. Usually, database/sql retries a request, assuming that the error occurs in a function that could be called first after retrieving a connection from the pool. But beginTx in clickhouse-go doesn't perform any network interaction and driver.ErrBadConn is returned later in the transaction. database/sql doesn't retry it because assumes that connection is alive - beginTx didn't return the error. This commit adds a method to check the connection liveness and performs that check in beginTx function. The check is taken from go-sql-driver/mysql#934. There is no way to check the liveness of a secure connection, as long as there is no access to raw TCP net.Conn in clickhouse-go.
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Damir Sayfutdinov
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Oct 8, 2021
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,57 @@ | ||
| // +build linux darwin dragonfly freebsd netbsd openbsd solaris illumos | ||
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| package clickhouse | ||
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| import ( | ||
| "errors" | ||
| "fmt" | ||
| "io" | ||
| "syscall" | ||
| "time" | ||
| ) | ||
|
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| var errUnexpectedRead = errors.New("unexpected read from socket") | ||
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| func (conn *connect) connCheck() error { | ||
| var sysErr error | ||
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| sysConn, ok := conn.Conn.(syscall.Conn) | ||
| if !ok { | ||
| return nil | ||
| } | ||
| rawConn, err := sysConn.SyscallConn() | ||
| if err != nil { | ||
| return err | ||
| } | ||
| // If this connection has a ReadTimeout which we've been setting on | ||
| // reads, reset it to zero value before we attempt a non-blocking | ||
| // read, otherwise we may get os.ErrDeadlineExceeded for the cached | ||
| // connection from the pool with an expired timeout. | ||
| if conn.readTimeout != 0 { | ||
| err = conn.SetReadDeadline(time.Time{}) | ||
| if err != nil { | ||
| return fmt.Errorf("set read deadline: %w", err) | ||
| } | ||
| conn.lastReadDeadlineTime = time.Time{} | ||
| } | ||
| err = rawConn.Read(func(fd uintptr) bool { | ||
| var buf [1]byte | ||
| n, err := syscall.Read(int(fd), buf[:]) | ||
| switch { | ||
| case n == 0 && err == nil: | ||
| sysErr = io.EOF | ||
| case n > 0: | ||
| sysErr = errUnexpectedRead | ||
| case err == syscall.EAGAIN || err == syscall.EWOULDBLOCK: | ||
| sysErr = nil | ||
| default: | ||
| sysErr = err | ||
| } | ||
| return true | ||
| }) | ||
| if err != nil { | ||
| return err | ||
| } | ||
|
|
||
| return sysErr | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,9 @@ | ||
| // +build !linux,!darwin,!dragonfly,!freebsd,!netbsd,!openbsd,!solaris,!illumos | ||
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| package clickhouse | ||
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| import "net" | ||
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| func connCheck(conn net.Conn) error { | ||
| return nil | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,85 @@ | ||
| package clickhouse | ||
|
|
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| import ( | ||
| "context" | ||
| "database/sql" | ||
| "database/sql/driver" | ||
| "testing" | ||
| "time" | ||
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| "github.com/stretchr/testify/assert" | ||
| ) | ||
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| func Test_ConnCheck(t *testing.T) { | ||
| const ( | ||
| ddl = ` | ||
| CREATE TABLE clickhouse_test_conncheck ( | ||
| Value String | ||
| ) Engine = Memory | ||
| ` | ||
| dml = ` | ||
| INSERT INTO clickhouse_test_conncheck | ||
| VALUES (?) | ||
| ` | ||
| ) | ||
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| if connect, err := sql.Open("clickhouse", "tcp://127.0.0.1:9000?debug=false"); assert.NoError(t, err) { | ||
| // We could change settings only at session level. | ||
| // If we have only 1 connection, we guarantee that we change settings for them. | ||
| connect.SetMaxOpenConns(1) | ||
| if _, err := connect.Exec("DROP TABLE IF EXISTS clickhouse_test_conncheck"); assert.NoError(t, err) { | ||
| if _, err := connect.Exec(ddl); assert.NoError(t, err) { | ||
| _, err = connect.Exec("set idle_connection_timeout=1") | ||
| assert.NoError(t, err) | ||
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| _, err = connect.Exec("set tcp_keep_alive_timeout=0") | ||
| assert.NoError(t, err) | ||
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| time.Sleep(1100 * time.Millisecond) | ||
| ctx := context.Background() | ||
| tx, err := connect.BeginTx(ctx, nil) | ||
| assert.NoError(t, err) | ||
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| _, err = tx.PrepareContext(ctx, dml) | ||
| assert.NoError(t, err) | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| func Test_ConnCheckNegative(t *testing.T) { | ||
| const ( | ||
| ddl = ` | ||
| CREATE TABLE clickhouse_test_conncheck_negative ( | ||
| Value String | ||
| ) Engine = Memory | ||
| ` | ||
| dml = ` | ||
| INSERT INTO clickhouse_test_conncheck_negative | ||
| VALUES (?) | ||
| ` | ||
| ) | ||
|
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| if connect, err := sql.Open("clickhouse", "tcp://127.0.0.1:9000?debug=true&check_connection_liveness=false"); assert.NoError(t, err) { | ||
| // We can only change the settings at the connection level. | ||
| // If we have only one connection, we change the settings specifically for that connection. | ||
| connect.SetMaxOpenConns(1) | ||
| if _, err := connect.Exec("DROP TABLE IF EXISTS clickhouse_test_conncheck_negative"); assert.NoError(t, err) { | ||
| if _, err := connect.Exec(ddl); assert.NoError(t, err) { | ||
| _, err = connect.Exec("set idle_connection_timeout=1") | ||
| assert.NoError(t, err) | ||
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| _, err = connect.Exec("set tcp_keep_alive_timeout=0") | ||
| assert.NoError(t, err) | ||
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| time.Sleep(1100 * time.Millisecond) | ||
| ctx := context.Background() | ||
| tx, err := connect.BeginTx(ctx, nil) | ||
| assert.NoError(t, err) | ||
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| _, err = tx.PrepareContext(ctx, dml) | ||
| assert.Equal(t, driver.ErrBadConn, err) | ||
| } | ||
| } | ||
| } | ||
| } |