1// Copyright 2015 The etcd Authors
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15package raft
16
17import (
18	"errors"
19
20	pb "go.etcd.io/etcd/raft/raftpb"
21)
22
23// Bootstrap initializes the RawNode for first use by appending configuration
24// changes for the supplied peers. This method returns an error if the Storage
25// is nonempty.
26//
27// It is recommended that instead of calling this method, applications bootstrap
28// their state manually by setting up a Storage that has a first index > 1 and
29// which stores the desired ConfState as its InitialState.
30func (rn *RawNode) Bootstrap(peers []Peer) error {
31	if len(peers) == 0 {
32		return errors.New("must provide at least one peer to Bootstrap")
33	}
34	lastIndex, err := rn.raft.raftLog.storage.LastIndex()
35	if err != nil {
36		return err
37	}
38
39	if lastIndex != 0 {
40		return errors.New("can't bootstrap a nonempty Storage")
41	}
42
43	// We've faked out initial entries above, but nothing has been
44	// persisted. Start with an empty HardState (thus the first Ready will
45	// emit a HardState update for the app to persist).
46	rn.prevHardSt = emptyState
47
48	// TODO(tbg): remove StartNode and give the application the right tools to
49	// bootstrap the initial membership in a cleaner way.
50	rn.raft.becomeFollower(1, None)
51	ents := make([]pb.Entry, len(peers))
52	for i, peer := range peers {
53		cc := pb.ConfChange{Type: pb.ConfChangeAddNode, NodeID: peer.ID, Context: peer.Context}
54		data, err := cc.Marshal()
55		if err != nil {
56			return err
57		}
58
59		ents[i] = pb.Entry{Type: pb.EntryConfChange, Term: 1, Index: uint64(i + 1), Data: data}
60	}
61	rn.raft.raftLog.append(ents...)
62
63	// Now apply them, mainly so that the application can call Campaign
64	// immediately after StartNode in tests. Note that these nodes will
65	// be added to raft twice: here and when the application's Ready
66	// loop calls ApplyConfChange. The calls to addNode must come after
67	// all calls to raftLog.append so progress.next is set after these
68	// bootstrapping entries (it is an error if we try to append these
69	// entries since they have already been committed).
70	// We do not set raftLog.applied so the application will be able
71	// to observe all conf changes via Ready.CommittedEntries.
72	//
73	// TODO(bdarnell): These entries are still unstable; do we need to preserve
74	// the invariant that committed < unstable?
75	rn.raft.raftLog.committed = uint64(len(ents))
76	for _, peer := range peers {
77		rn.raft.applyConfChange(pb.ConfChange{NodeID: peer.ID, Type: pb.ConfChangeAddNode}.AsV2())
78	}
79	return nil
80}
81