lib/handshake: log read/write operation duration on connection errors

This improve debuggability of network errors

app/vmstorage/transport/server.go

@@ -311,7 +311,7 @@ func (s *Server) processVMInsertConn(bc *handshake.BufferedConn) error {
 		}
 		reqBuf = bytesutil.Resize(reqBuf, int(packetSize))
 		if n, err := io.ReadFull(bc, reqBuf); err != nil {
-			return fmt.Errorf("cannot read packet with size %d: %w; read only %d bytes", packetSize, err, n)
+			return fmt.Errorf("cannot read packet with size %d bytes: %w; read only %d bytes", packetSize, err, n)
 		}
 		// Send `ack` to vminsert that the packet has been received.
 		deadline := time.Now().Add(5 * time.Second)

lib/handshake/buffered_conn.go

@@ -2,8 +2,10 @@ package handshake
 
 import (
 	"bufio"
+	"fmt"
 	"io"
 	"net"
+	"time"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/encoding/zstd"
 )
@@ -43,14 +45,24 @@ func newBufferedConn(c net.Conn, compressionLevel int, isReadCompressed bool) *B
 
 // Read reads up to len(p) from bc to p.
 func (bc *BufferedConn) Read(p []byte) (int, error) {
-	return bc.br.Read(p)
+	startTime := time.Now()
+	n, err := bc.br.Read(p)
+	if err != nil {
+		err = fmt.Errorf("cannot read data in %.3f seconds: %w", time.Since(startTime).Seconds(), err)
+	}
+	return n, err
 }
 
 // Write writes p to bc.
 //
 // Do not forget to call Flush if needed.
 func (bc *BufferedConn) Write(p []byte) (int, error) {
-	return bc.bw.Write(p)
+	startTime := time.Now()
+	n, err := bc.bw.Write(p)
+	if err != nil {
+		err = fmt.Errorf("cannot write data in %.3f seconds: %w", time.Since(startTime).Seconds(), err)
+	}
+	return n, err
 }
 
 // Close closes bc.