From b101064f8b88cdfe719326430e40f43414af9990 Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@gmail.com>
Date: Wed, 11 Sep 2019 14:11:37 +0300
Subject: [PATCH] all: report the number of bytes read on io.ReadFull error

This should simplify error investigation similar to https://github.com/VictoriaMetrics/VictoriaMetrics/issues/175
---
 app/vmselect/netstorage/netstorage.go | 4 ++--
 app/vmstorage/transport/server.go     | 8 ++++----
 lib/handshake/handshake.go            | 4 ++--
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/app/vmselect/netstorage/netstorage.go b/app/vmselect/netstorage/netstorage.go
index 5f61882c3..ff3d53925 100644
--- a/app/vmselect/netstorage/netstorage.go
+++ b/app/vmselect/netstorage/netstorage.go
@@ -1296,8 +1296,8 @@ func readBytes(buf []byte, bc *handshake.BufferedConn, maxDataSize int) ([]byte,
 	if dataSize == 0 {
 		return buf, nil
 	}
-	if _, err := io.ReadFull(bc, buf); err != nil {
-		return buf, fmt.Errorf("cannot read data with size %d: %s", dataSize, err)
+	if n, err := io.ReadFull(bc, buf); err != nil {
+		return buf, fmt.Errorf("cannot read data with size %d: %s; read only %d bytes", dataSize, err, n)
 	}
 	return buf, nil
 }
diff --git a/app/vmstorage/transport/server.go b/app/vmstorage/transport/server.go
index 2fcdcdea7..b09e07d0c 100644
--- a/app/vmstorage/transport/server.go
+++ b/app/vmstorage/transport/server.go
@@ -291,8 +291,8 @@ func (s *Server) processVMInsertConn(r io.Reader) error {
 			return fmt.Errorf("too big packet size: %d; shouldn't exceed %d", packetSize, consts.MaxInsertPacketSize)
 		}
 		buf = bytesutil.Resize(buf, int(packetSize))
-		if _, err := io.ReadFull(r, buf); err != nil {
-			return fmt.Errorf("cannot read packet with size %d: %s", packetSize, err)
+		if n, err := io.ReadFull(r, buf); err != nil {
+			return fmt.Errorf("cannot read packet with size %d: %s; read only %d bytes", packetSize, err, n)
 		}
 		vminsertPacketsRead.Inc()
 
@@ -386,8 +386,8 @@ func (ctx *vmselectRequestCtx) readDataBufBytes(maxDataSize int) error {
 	if dataSize == 0 {
 		return nil
 	}
-	if _, err := io.ReadFull(ctx.bc, ctx.dataBuf); err != nil {
-		return fmt.Errorf("cannot read data with size %d: %s", dataSize, err)
+	if n, err := io.ReadFull(ctx.bc, ctx.dataBuf); err != nil {
+		return fmt.Errorf("cannot read data with size %d: %s; read only %d bytes", dataSize, err, n)
 	}
 	return nil
 }
diff --git a/lib/handshake/handshake.go b/lib/handshake/handshake.go
index 0a71bdd1a..814611985 100644
--- a/lib/handshake/handshake.go
+++ b/lib/handshake/handshake.go
@@ -158,8 +158,8 @@ func readData(c net.Conn, dataLen int) ([]byte, error) {
 		return nil, fmt.Errorf("cannot set read deadline: %s", err)
 	}
 	data := make([]byte, dataLen)
-	if _, err := io.ReadFull(c, data); err != nil {
-		return nil, fmt.Errorf("cannot read message with size %d: %s", dataLen, err)
+	if n, err := io.ReadFull(c, data); err != nil {
+		return nil, fmt.Errorf("cannot read message with size %d: %s; read only %d bytes", dataLen, err, n)
 	}
 	if err := c.SetReadDeadline(zeroTime); err != nil {
 		return nil, fmt.Errorf("cannot reset read deadline: %s", err)