1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187
|
// Copyright 2017 Canonical Ltd.
//
// 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 fsms
import (
"encoding/binary"
"io"
"log"
"sync"
"github.com/CanonicalLtd/raft-test/internal/event"
"github.com/hashicorp/raft"
"github.com/pkg/errors"
)
// Wraps a raft.FSM, adding control on logs, snapshots and restores.
type fsmWrapper struct {
logger *log.Logger
// ID of of the raft server associated with this FSM.
id raft.ServerID
// Wrapped FSM
fsm raft.FSM
// Total number of commands applied by this FSM.
commands uint64
// Total number of snapshots performed on this FSM.
snapshots uint64
// Total number of restores performed on this FSM.
restores uint64
// Events that should be fired when a certain command log is events.
events map[uint64][]*event.Event
mu sync.RWMutex
}
func newFSMWrapper(logger *log.Logger, id raft.ServerID, fsm raft.FSM) *fsmWrapper {
return &fsmWrapper{
logger: logger,
id: id,
fsm: fsm,
events: make(map[uint64][]*event.Event),
}
}
func (f *fsmWrapper) Apply(log *raft.Log) interface{} {
result := f.fsm.Apply(log)
f.mu.Lock()
f.commands++
f.mu.Unlock()
f.logger.Printf("[DEBUG] raft-test: fsm %s: applied %d", f.id, f.commands)
if events, ok := f.events[f.commands]; ok {
for _, event := range events {
event.Fire()
event.Block()
}
}
return result
}
// Snapshot always return a dummy snapshot and no error without doing
// anything.
func (f *fsmWrapper) Snapshot() (raft.FSMSnapshot, error) {
snapshot, err := f.fsm.Snapshot()
if snapshot != nil {
f.mu.Lock()
f.snapshots++
snapshot = &fsmSnapshotWrapper{
commands: f.commands,
snapshot: snapshot,
}
f.mu.Unlock()
}
return snapshot, err
}
// Restore always return a nil error without reading anything from
// the reader.
func (f *fsmWrapper) Restore(reader io.ReadCloser) error {
if err := binary.Read(reader, binary.LittleEndian, &f.commands); err != nil {
return errors.Wrap(err, "failed to restore commands count")
}
if err := f.fsm.Restore(reader); err != nil {
return errors.Wrap(err, "failed to perform restore on user's FSM")
}
if events, ok := f.events[f.commands]; ok {
for _, event := range events {
event.Fire()
event.Block()
}
}
f.mu.Lock()
f.restores++
f.mu.Unlock()
return nil
}
// This method must be called whenever the server associated with this FSM is
// about to transition to the leader state, and before any new command log is
// applied.
//
// It resets the internal state of the fsm, such as the list of applied command
// logs and the scheduled events.
func (f *fsmWrapper) electing() {
f.mu.Lock()
defer f.mu.Unlock()
for n := range f.events {
delete(f.events, n)
}
}
// Return an event that will fire when the n'th command log for the term is
// applied on this FSM. It's assumed that this FSM is associated with the
// current leader.
func (f *fsmWrapper) whenApplied(n uint64) *event.Event {
e := event.New()
f.mu.RLock()
defer f.mu.RUnlock()
if f.commands >= n {
// Fire immediately.
go e.Fire()
} else {
_, ok := f.events[n]
if !ok {
f.events[n] = make([]*event.Event, 0)
}
f.events[n] = append(f.events[n], e)
}
return e
}
// Return the total number of command logs applied by this FSM.
func (f *fsmWrapper) Commands() uint64 {
return f.commands
}
// Return the total number of snapshots performed by this FSM.
func (f *fsmWrapper) Snapshots() uint64 {
return f.snapshots
}
// Return the total number of restores performed by this FSM.
func (f *fsmWrapper) Restores() uint64 {
return f.restores
}
type fsmSnapshotWrapper struct {
commands uint64
snapshot raft.FSMSnapshot
}
func (s *fsmSnapshotWrapper) Persist(sink raft.SnapshotSink) error {
// Augment the snapshot with the current command count.
if err := binary.Write(sink, binary.LittleEndian, s.commands); err != nil {
return errors.Wrap(err, "failed to augment snapshot with commands count")
}
if err := s.snapshot.Persist(sink); err != nil {
return errors.Wrap(err, "failed to perform snapshot on user's FSM")
}
return nil
}
func (s *fsmSnapshotWrapper) Release() {}
|