lib/protoparser: removed unnecessary call to SetReadDeadline when reading a stream of data

The OS should return any buffered data in the stream without the need to set the read timeout.

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/696

lib/protoparser/common/lines_reader.go

@@ -2,13 +2,10 @@ package common
 
 import (
 	"bytes"
-	"errors"
 	"fmt"
 	"io"
-	"net"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/bytesutil"
-	"github.com/VictoriaMetrics/VictoriaMetrics/lib/fasttime"
 )
 
 // The maximum size of a single line returned by ReadLinesBlock.
@@ -44,7 +41,6 @@ func ReadLinesBlockExt(r io.Reader, dstBuf, tailBuf []byte, maxLineLen int) ([]b
 	dstBuf = append(dstBuf[:0], tailBuf...)
 	tailBuf = tailBuf[:0]
 again:
-	startTime := fasttime.UnixTimestamp()
 	n, err := r.Read(dstBuf[len(dstBuf):cap(dstBuf)])
 	// Check for error only if zero bytes read from r, i.e. no forward progress made.
 	// Otherwise process the read data.
@@ -59,16 +55,6 @@ again:
 			// This fixes https://github.com/VictoriaMetrics/VictoriaMetrics/issues/60 .
 			return dstBuf, tailBuf, nil
 		}
-		var ne net.Error
-		if errors.As(err, &ne) && ne.Timeout() {
-			if fasttime.UnixTimestamp() == startTime {
-				// Prevent from busy loop when timeout erorrs are returned immediately.
-				// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/696 .
-				return dstBuf, tailBuf, fmt.Errorf("detected busy loop with repeated timeout error")
-			}
-			// Return empty results for an ordinary timeout.
-			return dstBuf, tailBuf, nil
-		}
 		return dstBuf, tailBuf, err
 	}
 	dstBuf = dstBuf[:len(dstBuf)+n]

lib/protoparser/graphite/streamparser.go

@@ -4,7 +4,6 @@ import (
 	"flag"
 	"fmt"
 	"io"
-	"net"
 	"runtime"
 	"sync"
 	"time"
@@ -37,20 +36,11 @@ func ParseStream(r io.Reader, callback func(rows []Row) error) error {
 	return ctx.Error()
 }
 
-const flushTimeout = 3 * time.Second
-
 func (ctx *streamContext) Read(r io.Reader) bool {
 	readCalls.Inc()
 	if ctx.err != nil {
 		return false
 	}
-	if c, ok := r.(net.Conn); ok {
-		if err := c.SetReadDeadline(time.Now().Add(flushTimeout)); err != nil {
-			readErrors.Inc()
-			ctx.err = fmt.Errorf("cannot set read deadline: %w", err)
-			return false
-		}
-	}
 	ctx.reqBuf, ctx.tailBuf, ctx.err = common.ReadLinesBlock(r, ctx.reqBuf, ctx.tailBuf)
 	if ctx.err != nil {
 		if ctx.err != io.EOF {

lib/protoparser/opentsdb/streamparser.go

@@ -4,7 +4,6 @@ import (
 	"flag"
 	"fmt"
 	"io"
-	"net"
 	"runtime"
 	"sync"
 	"time"
@@ -36,20 +35,11 @@ func ParseStream(r io.Reader, callback func(rows []Row) error) error {
 	return ctx.Error()
 }
 
-const flushTimeout = 3 * time.Second
-
 func (ctx *streamContext) Read(r io.Reader) bool {
 	readCalls.Inc()
 	if ctx.err != nil {
 		return false
 	}
-	if c, ok := r.(net.Conn); ok {
-		if err := c.SetReadDeadline(time.Now().Add(flushTimeout)); err != nil {
-			readErrors.Inc()
-			ctx.err = fmt.Errorf("cannot set read deadline: %w", err)
-			return false
-		}
-	}
 	ctx.reqBuf, ctx.tailBuf, ctx.err = common.ReadLinesBlock(r, ctx.reqBuf, ctx.tailBuf)
 	if ctx.err != nil {
 		if ctx.err != io.EOF {

lib/protoparser/prometheus/streamparser.go

@@ -3,7 +3,6 @@ package prometheus
 import (
 	"fmt"
 	"io"
-	"net"
 	"runtime"
 	"sync"
 	"time"
@@ -37,20 +36,11 @@ func ParseStream(r io.Reader, isGzipped bool, callback func(rows []Row) error) e
 	return ctx.Error()
 }
 
-const flushTimeout = 3 * time.Second
-
 func (ctx *streamContext) Read(r io.Reader) bool {
 	readCalls.Inc()
 	if ctx.err != nil {
 		return false
 	}
-	if c, ok := r.(net.Conn); ok {
-		if err := c.SetReadDeadline(time.Now().Add(flushTimeout)); err != nil {
-			readErrors.Inc()
-			ctx.err = fmt.Errorf("cannot set read deadline: %w", err)
-			return false
-		}
-	}
 	ctx.reqBuf, ctx.tailBuf, ctx.err = common.ReadLinesBlock(r, ctx.reqBuf, ctx.tailBuf)
 	if ctx.err != nil {
 		if ctx.err != io.EOF {