app/vminsert: fix inifinite loop when reading two lines without newline in the end

Fixes https://github.com/VictoriaMetrics/VictoriaMetrics/issues/82

app/vminsert/common/lines_reader.go

@@ -24,6 +24,7 @@ func ReadLinesBlock(r io.Reader, dstBuf, tailBuf []byte) ([]byte, []byte, error)
 		dstBuf = bytesutil.Resize(dstBuf, defaultBlockSize)
 	}
 	dstBuf = append(dstBuf[:0], tailBuf...)
+	tailBuf = tailBuf[:0]
 again:
 	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.
@@ -34,7 +35,7 @@ again:
 		}
 		if err == io.EOF && len(dstBuf) > 0 {
 			// Missing newline in the end of stream. This is OK,
-			/// so suppress io.EOF for now. It will be returned during the next
+			// so suppress io.EOF for now. It will be returned during the next
 			// call to ReadLinesBlock.
 			// This fixes https://github.com/VictoriaMetrics/VictoriaMetrics/issues/60 .
 			return dstBuf, tailBuf, nil

app/vminsert/common/lines_reader_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"reflect"
 	"testing"
 )
 
@@ -40,7 +41,73 @@ func (fr *failureReader) Read(p []byte) (int, error) {
 	return 0, fmt.Errorf("some error")
 }
 
-func TestReadLineBlockSuccessSingleByteReader(t *testing.T) {
+func TestReadLinesBlockMultiLinesSingleByteReader(t *testing.T) {
+	f := func(s string, linesExpected []string) {
+		t.Helper()
+
+		r := &singleByteReader{
+			b: []byte(s),
+		}
+		var err error
+		var dstBuf, tailBuf []byte
+		var lines []string
+		for {
+			dstBuf, tailBuf, err = ReadLinesBlock(r, dstBuf, tailBuf)
+			if err != nil {
+				if err == io.EOF {
+					break
+				}
+				t.Fatalf("unexpected error in ReadLinesBlock(%q): %s", s, err)
+			}
+			lines = append(lines, string(dstBuf))
+		}
+		if !reflect.DeepEqual(lines, linesExpected) {
+			t.Fatalf("unexpected lines after reading %q: got %q; want %q", s, lines, linesExpected)
+		}
+	}
+
+	f("", nil)
+	f("foo", []string{"foo"})
+	f("foo\n", []string{"foo"})
+	f("foo\nbar", []string{"foo", "bar"})
+	f("\nfoo\nbar", []string{"", "foo", "bar"})
+	f("\nfoo\nbar\n", []string{"", "foo", "bar"})
+	f("\nfoo\nbar\n\n", []string{"", "foo", "bar", ""})
+}
+
+func TestReadLinesBlockMultiLinesBytesBuffer(t *testing.T) {
+	f := func(s string, linesExpected []string) {
+		t.Helper()
+
+		r := bytes.NewBufferString(s)
+		var err error
+		var dstBuf, tailBuf []byte
+		var lines []string
+		for {
+			dstBuf, tailBuf, err = ReadLinesBlock(r, dstBuf, tailBuf)
+			if err != nil {
+				if err == io.EOF {
+					break
+				}
+				t.Fatalf("unexpected error in ReadLinesBlock(%q): %s", s, err)
+			}
+			lines = append(lines, string(dstBuf))
+		}
+		if !reflect.DeepEqual(lines, linesExpected) {
+			t.Fatalf("unexpected lines after reading %q: got %q; want %q", s, lines, linesExpected)
+		}
+	}
+
+	f("", nil)
+	f("foo", []string{"foo"})
+	f("foo\n", []string{"foo"})
+	f("foo\nbar", []string{"foo", "bar"})
+	f("\nfoo\nbar", []string{"\nfoo", "bar"})
+	f("\nfoo\nbar\n", []string{"\nfoo\nbar"})
+	f("\nfoo\nbar\n\n", []string{"\nfoo\nbar\n"})
+}
+
+func TestReadLinesBlockSuccessSingleByteReader(t *testing.T) {
 	f := func(s, dstBufExpected, tailBufExpected string) {
 		t.Helper()
 
@@ -87,7 +154,7 @@ func TestReadLineBlockSuccessSingleByteReader(t *testing.T) {
 	f(string(b), string(b[:maxLineSize]), "")
 }
 
-func TestReadLineBlockSuccessBytesBuffer(t *testing.T) {
+func TestReadLinesBlockSuccessBytesBuffer(t *testing.T) {
 	f := func(s, dstBufExpected, tailBufExpected string) {
 		t.Helper()
 

app/vminsert/influx/parser_test.go

@@ -348,4 +348,30 @@ func TestRowsUnmarshalSuccess(t *testing.T) {
 			},
 		},
 	})
+	// No newline after the second line.
+	// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/82
+	f("foo,tag=xyz field=1.23 48934\n"+
+		"bar x=-1i", &Rows{
+		Rows: []Row{
+			{
+				Measurement: "foo",
+				Tags: []Tag{{
+					Key:   "tag",
+					Value: "xyz",
+				}},
+				Fields: []Field{{
+					Key:   "field",
+					Value: 1.23,
+				}},
+				Timestamp: 48934,
+			},
+			{
+				Measurement: "bar",
+				Fields: []Field{{
+					Key:   "x",
+					Value: -1,
+				}},
+			},
+		},
+	})
 }