Add ability to handle context cancellations for TCP protocol (#1389)

* Add ability to handle context cancellations.

* Fixed ability to handle context cancellations.

* Removed obsolete comments.

* Added missing change.

* Fixed data race on connection close().

* Synchronisation fix.

* Fixed data race on connection close().

* Sync conn.close() calls eparately. Add test.

* Add one more test.

* Final clean-up.

* Close net connection first, to release blocked reader, then all pending ops on that connection will be properly released.

* Make new tests pretty.

* Clean-up.

.gitignore

@@ -27,6 +27,7 @@ _testmain.go
 
 coverage.txt
 .idea/**
+.vscode/**
 dev/*
 .run/**
 

conn.go

@@ -25,6 +25,7 @@ import (
 	"log"
 	"net"
 	"os"
+	"sync"
 	"syscall"
 	"time"
 
@@ -42,6 +43,7 @@ func dial(ctx context.Context, addr string, num int, opt *Options) (*connect, er
 		conn   net.Conn
 		debugf = func(format string, v ...any) {}
 	)
+
 	switch {
 	case opt.DialContext != nil:
 		conn, err = opt.DialContext(ctx, addr)
@@ -53,9 +55,11 @@ func dial(ctx context.Context, addr string, num int, opt *Options) (*connect, er
 			conn, err = net.DialTimeout("tcp", addr, opt.DialTimeout)
 		}
 	}
+
 	if err != nil {
 		return nil, err
 	}
+
 	if opt.Debug {
 		if opt.Debugf != nil {
 			debugf = func(format string, v ...any) {
@@ -68,6 +72,7 @@ func dial(ctx context.Context, addr string, num int, opt *Options) (*connect, er
 			debugf = log.New(os.Stdout, fmt.Sprintf("[clickhouse][conn=%d][%s]", num, conn.RemoteAddr()), 0).Printf
 		}
 	}
+
 	compression := CompressionNone
 	if opt.Compression != nil {
 		switch opt.Compression.Method {
@@ -96,9 +101,11 @@ func dial(ctx context.Context, addr string, num int, opt *Options) (*connect, er
 			maxCompressionBuffer: opt.MaxCompressionBuffer,
 		}
 	)
+
 	if err := connect.handshake(opt.Auth.Database, opt.Auth.Username, opt.Auth.Password); err != nil {
 		return nil, err
 	}
+
 	if connect.revision >= proto.DBMS_MIN_PROTOCOL_VERSION_WITH_ADDENDUM {
 		if err := connect.sendAddendum(); err != nil {
 			return nil, err
@@ -109,6 +116,7 @@ func dial(ctx context.Context, addr string, num int, opt *Options) (*connect, er
 	if num == 1 && !resources.ClientMeta.IsSupportedClickHouseVersion(connect.server.Version) {
 		debugf("[handshake] WARNING: version %v of ClickHouse is not supported by this client - client supports %v", connect.server.Version, resources.ClientMeta.SupportedVersions())
 	}
+
 	return connect, nil
 }
 
@@ -131,6 +139,8 @@ type connect struct {
 	readTimeout          time.Duration
 	blockBufferSize      uint8
 	maxCompressionBuffer int
+	readerMutex          sync.Mutex
+	closeMutex           sync.Mutex
 }
 
 func (c *connect) settings(querySettings Settings) []proto.Setting {
@@ -153,15 +163,16 @@ func (c *connect) settings(querySettings Settings) []proto.Setting {
 	for k, v := range c.opt.Settings {
 		settings = append(settings, settingToProtoSetting(k, v))
 	}
+
 	for k, v := range querySettings {
 		settings = append(settings, settingToProtoSetting(k, v))
 	}
+
 	return settings
 }
 
 func (c *connect) isBad() bool {
-	switch {
-	case c.closed:
+	if c.isClosed() {
 		return true
 	}
 
@@ -172,19 +183,43 @@ func (c *connect) isBad() bool {
 	if err := c.connCheck(); err != nil {
 		return true
 	}
+
 	return false
 }
 
+func (c *connect) isClosed() bool {
+	c.closeMutex.Lock()
+	defer c.closeMutex.Unlock()
+
+	return c.closed
+}
+
+func (c *connect) setClosed() {
+	c.closeMutex.Lock()
+	defer c.closeMutex.Unlock()
+
+	c.closed = true
+}
+
 func (c *connect) close() error {
+	c.closeMutex.Lock()
 	if c.closed {
+		c.closeMutex.Unlock()
 		return nil
 	}
 	c.closed = true
-	c.buffer = nil
-	c.reader = nil
+	c.closeMutex.Unlock()
+
 	if err := c.conn.Close(); err != nil {
 		return err
 	}
+
+	c.buffer = nil
+
+	c.readerMutex.Lock()
+	c.reader = nil
+	c.readerMutex.Unlock()
+
 	return nil
 }
 
@@ -193,6 +228,7 @@ func (c *connect) progress() (*Progress, error) {
 	if err := progress.Decode(c.reader, c.revision); err != nil {
 		return nil, err
 	}
+
 	c.debugf("[progress] %s", &progress)
 	return &progress, nil
 }
@@ -202,6 +238,7 @@ func (c *connect) exception() error {
 	if err := e.Decode(c.reader); err != nil {
 		return err
 	}
+
 	c.debugf("[exception] %s", e.Error())
 	return &e
 }
@@ -218,6 +255,12 @@ func (c *connect) compressBuffer(start int) error {
 }
 
 func (c *connect) sendData(block *proto.Block, name string) error {
+	if c.isClosed() {
+		err := errors.New("attempted sending on closed connection")
+		c.debugf("[send data] err: %v", err)
+		return err
+	}
+
 	c.debugf("[send data] compression=%q", c.compression)
 	c.buffer.PutByte(proto.ClientData)
 	c.buffer.PutString(name)
@@ -227,6 +270,7 @@ func (c *connect) sendData(block *proto.Block, name string) error {
 	if err := block.EncodeHeader(c.buffer, c.revision); err != nil {
 		return err
 	}
+
 	for i := range block.Columns {
 		if err := block.EncodeColumn(c.buffer, c.revision, i); err != nil {
 			return err
@@ -242,33 +286,50 @@ func (c *connect) sendData(block *proto.Block, name string) error {
 			compressionOffset = 0
 		}
 	}
+
 	if err := c.compressBuffer(compressionOffset); err != nil {
 		return err
 	}
+
 	if err := c.flush(); err != nil {
 		switch {
 		case errors.Is(err, syscall.EPIPE):
 			c.debugf("[send data] pipe is broken, closing connection")
-			c.closed = true
+			c.setClosed()
 		case errors.Is(err, io.EOF):
 			c.debugf("[send data] unexpected EOF, closing connection")
-			c.closed = true
+			c.setClosed()
 		default:
 			c.debugf("[send data] unexpected error: %v", err)
 		}
 		return err
 	}
+
 	defer func() {
 		c.buffer.Reset()
 	}()
+
 	return nil
 }
 
 func (c *connect) readData(ctx context.Context, packet byte, compressible bool) (*proto.Block, error) {
+	if c.isClosed() {
+		err := errors.New("attempted reading on closed connection")
+		c.debugf("[read data] err: %v", err)
+		return nil, err
+	}
+
+	if c.reader == nil {
+		err := errors.New("attempted reading on nil reader")
+		c.debugf("[read data] err: %v", err)
+		return nil, err
+	}
+
 	if _, err := c.reader.Str(); err != nil {
 		c.debugf("[read data] str error: %v", err)
 		return nil, err
 	}
+
 	if compressible && c.compression != CompressionNone {
 		c.reader.EnableCompression()
 		defer c.reader.DisableCompression()
@@ -285,6 +346,7 @@ func (c *connect) readData(ctx context.Context, packet byte, compressible bool)
 		c.debugf("[read data] decode error: %v", err)
 		return nil, err
 	}
+
 	block.Packet = packet
 	c.debugf("[read data] compression=%q. block: columns=%d, rows=%d", c.compression, len(block.Columns), block.Rows())
 	return &block, nil
@@ -295,10 +357,12 @@ func (c *connect) flush() error {
 		// Nothing to flush.
 		return nil
 	}
+
 	n, err := c.conn.Write(c.buffer.Buf)
 	if err != nil {
 		return errors.Wrap(err, "write")
 	}
+
 	if n != len(c.buffer.Buf) {
 		return errors.New("wrote less than expected")
 	}