raft_flow_control_test.go

// Copyright 2015 The etcd Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package raft

import (
	"testing"

	"github.com/stretchr/testify/require"

	pb "go.etcd.io/raft/v3/raftpb"
)

// TestMsgAppFlowControlFull ensures:
// 1. msgApp can fill the sending window until full
// 2. when the window is full, no more msgApp can be sent.

func TestMsgAppFlowControlFull(t *testing.T) {
	r := newTestRaft(1, 5, 1, newTestMemoryStorage(withPeers(1, 2)))
	r.becomeCandidate()
	r.becomeLeader()

	pr2 := r.trk.Progress[2]
	// force the progress to be in replicate state
	pr2.BecomeReplicate()
	// fill in the inflights window
	for i := 0; i < r.trk.MaxInflight; i++ {
		r.Step(pb.Message{From: 1, To: 1, Type: pb.MsgProp, Entries: []pb.Entry{{Data: []byte("somedata")}}})
		ms := r.readMessages()
		require.Len(t, ms, 1)
		require.Equal(t, pb.MsgApp, ms[0].Type)
	}

	// ensure 1
	require.True(t, pr2.IsPaused())

	// ensure 2
	for i := 0; i < 10; i++ {
		r.Step(pb.Message{From: 1, To: 1, Type: pb.MsgProp, Entries: []pb.Entry{{Data: []byte("somedata")}}})
		ms := r.readMessages()
		require.Empty(t, ms)
	}
}

// TestMsgAppFlowControlMoveForward ensures msgAppResp can move
// forward the sending window correctly:
// 1. valid msgAppResp.index moves the windows to pass all smaller or equal index.
// 2. out-of-dated msgAppResp has no effect on the sliding window.
func TestMsgAppFlowControlMoveForward(t *testing.T) {
	r := newTestRaft(1, 5, 1, newTestMemoryStorage(withPeers(1, 2)))
	r.becomeCandidate()
	r.becomeLeader()

	pr2 := r.trk.Progress[2]
	// force the progress to be in replicate state
	pr2.BecomeReplicate()
	// fill in the inflights window
	for i := 0; i < r.trk.MaxInflight; i++ {
		r.Step(pb.Message{From: 1, To: 1, Type: pb.MsgProp, Entries: []pb.Entry{{Data: []byte("somedata")}}})
		r.readMessages()
	}

	// 1 is noop, 2 is the first proposal we just sent.
	// so we start with 2.
	for tt := 2; tt < r.trk.MaxInflight; tt++ {
		// move forward the window
		r.Step(pb.Message{From: 2, To: 1, Type: pb.MsgAppResp, Index: uint64(tt)})
		r.readMessages()

		// fill in the inflights window again
		r.Step(pb.Message{From: 1, To: 1, Type: pb.MsgProp, Entries: []pb.Entry{{Data: []byte("somedata")}}})
		ms := r.readMessages()
		require.Len(t, ms, 1)
		require.Equal(t, pb.MsgApp, ms[0].Type)

		// ensure 1
		require.True(t, pr2.IsPaused())

		// ensure 2
		for i := 0; i < tt; i++ {
			r.Step(pb.Message{From: 2, To: 1, Type: pb.MsgAppResp, Index: uint64(i)})
			require.True(t, pr2.IsPaused())
		}
	}
}

// TestMsgAppFlowControlRecvHeartbeat ensures a heartbeat response
// frees one slot if the window is full.
func TestMsgAppFlowControlRecvHeartbeat(t *testing.T) {
	r := newTestRaft(1, 5, 1, newTestMemoryStorage(withPeers(1, 2)))
	r.becomeCandidate()
	r.becomeLeader()

	pr2 := r.trk.Progress[2]
	// force the progress to be in replicate state
	pr2.BecomeReplicate()
	// fill in the inflights window
	for i := 0; i < r.trk.MaxInflight; i++ {
		r.Step(pb.Message{From: 1, To: 1, Type: pb.MsgProp, Entries: []pb.Entry{{Data: []byte("somedata")}}})
		r.readMessages()
	}

	for tt := 1; tt < 5; tt++ {
		// recv tt msgHeartbeatResp and expect one free slot
		for i := 0; i < tt; i++ {
			require.True(t, pr2.IsPaused())
			// Unpauses the progress, sends an empty MsgApp, and pauses it again.
			r.Step(pb.Message{From: 2, To: 1, Type: pb.MsgHeartbeatResp})
			ms := r.readMessages()
			require.Len(t, ms, 1)
			require.Equal(t, pb.MsgApp, ms[0].Type)
			require.Empty(t, ms[0].Entries)
		}

		// No more appends are sent if there are no heartbeats.
		for i := 0; i < 10; i++ {
			require.True(t, pr2.IsPaused())
			r.Step(pb.Message{From: 1, To: 1, Type: pb.MsgProp, Entries: []pb.Entry{{Data: []byte("somedata")}}})
			ms := r.readMessages()
			require.Empty(t, ms)
		}

		// clear all pending messages.
		r.Step(pb.Message{From: 2, To: 1, Type: pb.MsgHeartbeatResp})
		r.readMessages()
	}
}