From 27ea5d36c46107510962d54468b539b37057b416 Mon Sep 17 00:00:00 2001
From: Xiang Li <xiangli.cs@gmail.com>
Date: Fri, 1 Apr 2016 14:48:07 -0700
Subject: [PATCH] raft: refactor inflight

---
 raft/progress.go      | 29 +++++++++++++++++++----------
 raft/progress_test.go | 11 -----------
 2 files changed, 19 insertions(+), 21 deletions(-)

diff --git a/raft/progress.go b/raft/progress.go
index 11f53409d4c..c5dbb655649 100644
--- a/raft/progress.go
+++ b/raft/progress.go
@@ -64,12 +64,17 @@ type Progress struct {
 	RecentActive bool
 
 	// inflights is a sliding window for the inflight messages.
+	// Each inflight message might contain more than one entries
+	// and has a size limit defined in raft config as MaxSizePerMsg.
+	// Thus inflight effectively limits both the number of inflight messages
+	// and the bandwidth each Progress can use.
 	// When inflights is full, no more message should be sent.
 	// When a leader sends out a message, the index of the last
 	// entry should be added to inflights. The index MUST be added
 	// into inflights in order.
 	// When a leader receives a reply, the previous inflights should
-	// be freed by calling inflights.freeTo.
+	// be freed by calling inflights.freeTo with the index of the last
+	// received entry.
 	ins *inflights
 }
 
@@ -183,14 +188,13 @@ type inflights struct {
 	// number of inflights in the buffer
 	count int
 
-	// the size of the buffer
-	size   int
+	// buffer contains the index of the last entry
+	// inside one message.
 	buffer []uint64
 }
 
 func newInflights(size int) *inflights {
 	return &inflights{
-		size:   size,
 		buffer: make([]uint64, size),
 	}
 }
@@ -201,8 +205,9 @@ func (in *inflights) add(inflight uint64) {
 		panic("cannot add into a full inflights")
 	}
 	next := in.start + in.count
-	if next >= in.size {
-		next -= in.size
+	size := in.size()
+	if next >= size {
+		next -= size
 	}
 	in.buffer[next] = inflight
 	in.count++
@@ -220,10 +225,10 @@ func (in *inflights) freeTo(to uint64) {
 		if to < in.buffer[idx] { // found the first large inflight
 			break
 		}
-
+		size := in.size()
 		// increase index and maybe rotate
-		if idx++; idx >= in.size {
-			idx -= in.size
+		if idx++; idx >= size {
+			idx -= size
 		}
 	}
 	// free i inflights and set new start index
@@ -235,7 +240,11 @@ func (in *inflights) freeFirstOne() { in.freeTo(in.buffer[in.start]) }
 
 // full returns true if the inflights is full.
 func (in *inflights) full() bool {
-	return in.count == in.size
+	return in.count == len(in.buffer)
+}
+
+func (in *inflights) size() int {
+	return len(in.buffer)
 }
 
 // resets frees all inflights.
diff --git a/raft/progress_test.go b/raft/progress_test.go
index 4cea14e875a..3d80d534995 100644
--- a/raft/progress_test.go
+++ b/raft/progress_test.go
@@ -22,7 +22,6 @@ import (
 func TestInflightsAdd(t *testing.T) {
 	// no rotating case
 	in := &inflights{
-		size:   10,
 		buffer: make([]uint64, 10),
 	}
 
@@ -33,7 +32,6 @@ func TestInflightsAdd(t *testing.T) {
 	wantIn := &inflights{
 		start: 0,
 		count: 5,
-		size:  10,
 		//               ↓------------
 		buffer: []uint64{0, 1, 2, 3, 4, 0, 0, 0, 0, 0},
 	}
@@ -49,7 +47,6 @@ func TestInflightsAdd(t *testing.T) {
 	wantIn2 := &inflights{
 		start: 0,
 		count: 10,
-		size:  10,
 		//               ↓---------------------------
 		buffer: []uint64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
 	}
@@ -61,7 +58,6 @@ func TestInflightsAdd(t *testing.T) {
 	// rotating case
 	in2 := &inflights{
 		start:  5,
-		size:   10,
 		buffer: make([]uint64, 10),
 	}
 
@@ -72,7 +68,6 @@ func TestInflightsAdd(t *testing.T) {
 	wantIn21 := &inflights{
 		start: 5,
 		count: 5,
-		size:  10,
 		//                              ↓------------
 		buffer: []uint64{0, 0, 0, 0, 0, 0, 1, 2, 3, 4},
 	}
@@ -88,7 +83,6 @@ func TestInflightsAdd(t *testing.T) {
 	wantIn22 := &inflights{
 		start: 5,
 		count: 10,
-		size:  10,
 		//               -------------- ↓------------
 		buffer: []uint64{5, 6, 7, 8, 9, 0, 1, 2, 3, 4},
 	}
@@ -110,7 +104,6 @@ func TestInflightFreeTo(t *testing.T) {
 	wantIn := &inflights{
 		start: 5,
 		count: 5,
-		size:  10,
 		//                              ↓------------
 		buffer: []uint64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
 	}
@@ -124,7 +117,6 @@ func TestInflightFreeTo(t *testing.T) {
 	wantIn2 := &inflights{
 		start: 9,
 		count: 1,
-		size:  10,
 		//                                          ↓
 		buffer: []uint64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
 	}
@@ -143,7 +135,6 @@ func TestInflightFreeTo(t *testing.T) {
 	wantIn3 := &inflights{
 		start: 3,
 		count: 2,
-		size:  10,
 		//                           ↓-----
 		buffer: []uint64{10, 11, 12, 13, 14, 5, 6, 7, 8, 9},
 	}
@@ -157,7 +148,6 @@ func TestInflightFreeTo(t *testing.T) {
 	wantIn4 := &inflights{
 		start: 5,
 		count: 0,
-		size:  10,
 		//                                   ↓
 		buffer: []uint64{10, 11, 12, 13, 14, 5, 6, 7, 8, 9},
 	}
@@ -178,7 +168,6 @@ func TestInflightFreeFirstOne(t *testing.T) {
 	wantIn := &inflights{
 		start: 1,
 		count: 9,
-		size:  10,
 		//                  ↓------------------------
 		buffer: []uint64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
 	}