/
service.go
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/
service.go
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// Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserved.
// 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 pserver
import (
"bufio"
"bytes"
"encoding/binary"
"encoding/gob"
"encoding/json"
"errors"
"fmt"
"hash/crc32"
"io/ioutil"
"os"
"path"
"strconv"
"strings"
"sync"
"time"
"github.com/golang/protobuf/proto"
uuid "github.com/satori/go.uuid"
pb "github.com/PaddlePaddle/Paddle/go/proto"
log "github.com/inconshreveable/log15"
)
// ElementType is the type of elements of a Parameter.
type ElementType int
// ErrCheckpointNotFound indicates that the pserver checkpoint could
// not be found.
var ErrCheckpointNotFound = errors.New("checkpoint not found in etcd")
// RPC error message.
const (
AlreadyInitialized = "pserver already initialized"
Uninitialized = "pserver not fully initialized"
WrongChecksum = "checkpoint file checksum validation failed"
)
// Supported element types.
const (
Int32 ElementType = iota
UInt32
Int64
UInt64
Float32
Float64
)
// Parameter is a piece of data to sync with the parameter server.
type Parameter struct {
Name string
ElementType ElementType
Content []byte
}
func float32ToString(b []byte) string {
f := make([]float32, len(b)/4)
buf := bytes.NewReader(b)
err := binary.Read(buf, binary.LittleEndian, &f)
if err != nil {
return ""
}
return fmt.Sprintf("%v", f)
}
func float32ByteToString(c []byte) string {
var a []byte
var b []byte
if len(c) <= 80 {
a = c
} else {
a = c[0:40]
b = c[len(c)-40:]
}
var s string
s = float32ToString(a)
if b == nil {
return s
}
s = strings.Replace(s, "]", "", -1) + "..." + strings.Replace(float32ToString(b), "[", "", -1)
return s
}
func (p Parameter) String() string {
if p.ElementType != Float32 {
return fmt.Sprintf("name:%v ElementType:%v",
p.Name, p.ElementType)
}
return float32ByteToString(p.Content)
}
// ParameterWithConfig contains the parameter and the configuration.
type ParameterWithConfig struct {
Param Parameter
Config []byte // parameter configuration in Proto Buffer format
}
// checkpointMeta saves checkpoint metadata
type checkpointMeta struct {
UUID string `json:"uuid"`
Path string `json:"path"`
CRC32 uint32 `json:"crc32"`
Timestamp int64 `json:"timestamp"`
}
// Checkpoint is the pserver shard persist in file.
type Checkpoint []parameterCheckpoint
// Gradient is the gradient of the parameter.
type Gradient Parameter
// Service is the RPC service for pserver.
type Service struct {
initialized chan struct{}
idx int
checkpointInterval time.Duration
checkpointPath string
client KVStore
mu sync.Mutex
optMap map[string]*optimizer
}
// parameterCheckpoint saves parameter checkpoint.
type parameterCheckpoint struct {
ParameterWithConfig
State []byte
}
type KVStore interface {
GetKey(key string, timeout time.Duration) ([]byte, error)
PutKey(key string, value []byte, timeout time.Duration, withLease bool) error
}
func loadMeta(e KVStore, idx int) (meta checkpointMeta, err error) {
v, err := e.GetKey(PsCheckpoint+strconv.Itoa(idx), 3*time.Second)
if err != nil {
return
}
if len(v) == 0 {
err = ErrCheckpointNotFound
return
}
if err = json.Unmarshal(v, &meta); err != nil {
return
}
return
}
// LoadCheckpoint loads checkpoint from file.
func LoadCheckpoint(e KVStore, idx int) (Checkpoint, error) {
log.Info("Loading checkpoint", "pserver index", idx)
defer traceTime(time.Now(), "load checkpoint")
cpMeta, err := loadMeta(e, idx)
if err != nil {
return nil, err
}
content, err := ioutil.ReadFile(cpMeta.Path)
if err != nil {
return nil, err
}
crc32 := crc32.ChecksumIEEE(content)
if crc32 != cpMeta.CRC32 {
return nil, errors.New(WrongChecksum)
}
dec := gob.NewDecoder(bytes.NewReader(content))
var cp Checkpoint
if err = dec.Decode(&cp); err != nil {
return nil, err
}
return cp, nil
}
// NewService creates a new service, will bypass etcd registration if no
// endpoints specified. It will recovery from checkpoint file if a exists a specified checkpoint.
func NewService(idx int, interval time.Duration, path string, client KVStore, cp Checkpoint) (*Service, error) {
s := &Service{
idx: idx,
checkpointInterval: interval,
checkpointPath: path,
client: client,
}
s.optMap = make(map[string]*optimizer)
s.initialized = make(chan struct{})
if cp != nil {
for _, item := range cp {
p := ParameterWithConfig{
Param: item.Param,
Config: item.Config,
}
s.optMap[p.Param.Name] = newOptimizer(p, item.State)
}
close(s.initialized)
}
return s, nil
}
// InitParam initializes a parameter.
func (s *Service) InitParam(paramWithConfigs ParameterWithConfig, _ *int) error {
select {
case <-s.initialized:
log.Warn("init param called but parameters already initialized.")
return errors.New(AlreadyInitialized)
default:
}
c := &pb.OptimizerConfig{}
proto.Unmarshal(paramWithConfigs.Config, c)
log.Debug(fmt.Sprintf("OptimizerConfig:%v", c))
s.mu.Lock()
defer s.mu.Unlock()
// TODO(helin): check if paramWithConfigs.Param.Content is
// properly memory aligned, if not, make copy to a memory
// aligned region.
s.optMap[paramWithConfigs.Param.Name] = newOptimizer(paramWithConfigs, nil)
log.Info(
"init parameter",
"name", paramWithConfigs.Param.Name,
"config len", len(paramWithConfigs.Config),
"param len", len(paramWithConfigs.Param.Content),
"type", paramWithConfigs.Param.ElementType,
)
return nil
}
// FinishInitParams tells the parameter server that the parameter
// initialization has finished.
func (s *Service) FinishInitParams(_ int, _ *int) error {
select {
case <-s.initialized:
log.Warn("finished init param called but parameters already initialized.")
return errors.New(AlreadyInitialized)
default:
}
close(s.initialized)
go func() {
t := time.Tick(s.checkpointInterval)
for range t {
err := s.checkpoint()
if err != nil {
log.Error("checkpoint error", log.Ctx{"error": err})
}
}
}()
log.Info("init parameter finished.")
return nil
}
// SendGrad sends gradient to parameter servers for parameter
// optimization.
func (s *Service) SendGrad(g Gradient, _ *int) error {
select {
case <-s.initialized:
default:
log.Warn("received gradient before initialization.",
"name", g.Name, "size", len(g.Content), "type", g.ElementType)
return errors.New(Uninitialized)
}
s.mu.Lock()
defer s.mu.Unlock()
o, ok := s.optMap[g.Name]
if !ok {
log.Warn("received gradient but can't find name.",
"name", g.Name, "size", len(g.Content), "type", g.ElementType)
return fmt.Errorf("parameter: %s does not exist", g.Name)
}
log.Debug(Parameter(g).String())
log.Info("received gradient from trainer, updating gradient.",
"name", g.Name, "size", len(g.Content), "type", g.ElementType)
return o.UpdateParameter(g)
}
// GetParam gets parameters from the parameter server.
func (s *Service) GetParam(name string, parameter *Parameter) error {
<-s.initialized
s.mu.Lock()
defer s.mu.Unlock()
opt, ok := s.optMap[name]
if !ok {
log.Warn("trainer wants to get a parameter that does not exist.", "name", name)
return fmt.Errorf("parameter: %s does not exist", name)
}
// The parameter content (a byte slice) may change
// during RPC serialization due to write from other
// goroutine, we allow it since mini-batch based deep
// learning optimization methods are stochastic in
// nature. This race condition is allowed deliberately
// to save the program from making a copy of the
// parameter content.
parameter.Name = name
parameter.ElementType = opt.elementType
parameter.Content = opt.GetWeights()
log.Debug(parameter.String())
log.Info("sending parameter to the trainer", "name", parameter.Name, "size", len(parameter.Content), "type", parameter.ElementType)
return nil
}
func traceTime(start time.Time, name string) {
elapsed := time.Since(start)
log.Info("time elapsed", log.Ctx{"name": name, "elapsed": elapsed})
}
// checkpoint saves checkpoint to disk.
//
// checkpoint should be only called after the parameters are
// initialized.
func (s *Service) checkpoint() (err error) {
log.Info("Begin save checkpoint.")
defer traceTime(time.Now(), "save checkpoint")
s.mu.Lock()
cp := make([]parameterCheckpoint, len(s.optMap))
index := 0
// TODO(helin): write checkpoint incrementally to reduce memory
// footprint during checkpoint.
for name, opt := range s.optMap {
var pc parameterCheckpoint
pc.Param.Name = name
pc.Param.ElementType = opt.elementType
pc.Param.Content = opt.GetWeights()
pc.Config = opt.config
pc.State = opt.GetStates()
cp[index] = pc
index++
}
s.mu.Unlock()
var buf bytes.Buffer
encoder := gob.NewEncoder(&buf)
err = encoder.Encode(cp)
if err != nil {
return
}
if _, err = os.Stat(s.checkpointPath); os.IsNotExist(err) {
err = os.MkdirAll(s.checkpointPath, os.ModePerm)
if err != nil {
return
}
}
id := uuid.NewV4().String()
p := path.Join(s.checkpointPath, id)
f, err := os.Create(p)
if err != nil {
return
}
defer func() {
closeErr := f.Close()
if closeErr != nil {
if err != nil {
log.Error("error close checkpoint file", log.Ctx{"error": closeErr})
} else {
// Set closeErr as return value.
err = closeErr
}
}
}()
writer := bufio.NewWriter(f)
_, err = writer.Write(buf.Bytes())
if err != nil {
return
}
err = writer.Flush()
if err != nil {
return
}
oldMeta, err := loadMeta(s.client, s.idx)
if err == ErrCheckpointNotFound {
log.Info("old meta not found, skip removing old meta")
err = nil
} else if err == nil {
log.Info("removing old meta")
if oldMeta.Path != "" {
rmErr := os.Remove(oldMeta.Path)
if rmErr != nil {
// log error, but still treat checkpoint as
// successful.
log.Error("remove old meta file error", log.Ctx{"error": rmErr})
}
}
}
if err != nil {
return
}
crc32 := crc32.ChecksumIEEE(buf.Bytes())
cpMeta := checkpointMeta{
UUID: id,
Timestamp: time.Now().UnixNano(),
CRC32: crc32,
Path: p,
}
json, err := json.Marshal(cpMeta)
if err != nil {
return
}
err = s.client.PutKey(PsCheckpoint+strconv.Itoa(s.idx), json, 3*time.Second, false)
if err != nil {
return
}
return
}