/*
此api实现复制写入操作 步骤如下:
1.先写入本地
2. 如果需要复制则 将消息投递replicate到master
3. 如果2操作成功完成则返回
4. 如果2失败,则删除本地副本并投递删除消息到master
5. 返回4的结果
同理删除
*/
func ReplicatedWrite(masterNode string, s *storage.Store, volumeId storage.VolumeId, needle *storage.Needle, r *http.Request) (size uint32, errorStatus string) {
ret, err := s.Write(volumeId, needle)
needToReplicate := !s.HasVolume(volumeId)
if err != nil {
errorStatus = "Failed to write to local disk (" + err.Error() + ")"
} else if ret > 0 { //写入成功
needToReplicate = needToReplicate || s.GetVolume(volumeId).NeedToReplicate()
} else {
errorStatus = "Failed to write to local disk"
}
//??? --lewgun
if !needToReplicate && ret > 0 {
needToReplicate = s.GetVolume(volumeId).NeedToReplicate()
}
if needToReplicate { //send to other replica locations
if r.FormValue("type") != "replicate" { //只有最原始的才会执行distributedOperation
//向master复制
if !distributedOperation(masterNode,
s,
volumeId,
func(location operation.Location) bool {
_, err := operation.Upload(
"http://"+location.Url+r.URL.Path+"?type=replicate&ts="+strconv.FormatUint(needle.LastModified, 10),
string(needle.Name),
bytes.NewReader(needle.Data),
needle.IsGzipped(),
string(needle.Mime))
return err == nil
})
{
ret = 0
errorStatus = "Failed to write to replicas for volume " + volumeId.String()
}// if !distributedOperation(masterNode,
} // if r.FormValue("type") != "replicate" {
}
//复制失败,删除本地副本
if errorStatus != "" {
if _, err = s.Delete(volumeId, needle); err != nil {
errorStatus += "\nCannot delete " + strconv.FormatUint(needle.Id, 10) + " from " +
volumeId.String() + ": " + err.Error()
} else {
distributedOperation(
masterNode,
s,
volumeId,
func(location operation.Location) bool {
return nil == util.Delete("http://"+location.Url+r.URL.Path+"?type=replicate")
}
) // distributedOperation(...)
} // if errorStatus != "" {
}
size = ret
return
}
func distributedOperation(masterNode string, store *storage.Store, volumeId storage.VolumeId, op func(location operation.Location) bool) bool {
if lookupResult, lookupErr := operation.Lookup(masterNode, volumeId.String()); lookupErr == nil {
length := 0
selfUrl := (store.Ip + ":" + strconv.Itoa(store.Port))
results := make(chan bool)
for _, location := range lookupResult.Locations {
//排除自己
if location.Url != selfUrl {
length++
//异步复制
go func(location operation.Location, results chan bool) {
results <- op(location)
}(location, results)
}
}
ret := true
//等待操作结束 无论成功与否
for i := 0; i < length; i++ {
ret = ret && <-results
}
return ret
} else {
glog.V(0).Infoln("Failed to lookup for", volumeId, lookupErr.Error())
}
return false
}
//http://192.168.1.1:8080/admin/assign_volume
func AllocateVolume(dn *DataNode, vid storage.VolumeId, option *VolumeGrowOption) error {
values := make(url.Values)
values.Add("volume", vid.String())
values.Add("collection", option.Collection)
values.Add("replication", option.ReplicaPlacement.String())
values.Add("ttl", option.Ttl.String())
jsonBlob, err := util.Post("http://"+dn.PublicUrl+"/admin/assign_volume", values)
if err != nil {
return err
}
var ret AllocateVolumeResult
if err := json.Unmarshal(jsonBlob, &ret); err != nil {
return err
}
if ret.Error != "" {
return errors.New(ret.Error)
}
return nil
}
func (vg *VolumeGrowth) grow(topo *Topology, vid storage.VolumeId, option *VolumeGrowOption, servers ...*DataNode) error {
for _, server := range servers {
if err := AllocateVolume(server, vid, option); err == nil {
vi := storage.VolumeInfo{
Id: vid,
Size: 0,
Collection: option.Collection,
ReplicaPlacement: option.ReplicaPlacement,
Ttl: option.Ttl,
Version: storage.CurrentVersion,
}
server.AddOrUpdateVolume(vi)
topo.RegisterVolumeLayout(vi, server)
glog.V(0).Infoln("Created Volume", vid, "on", server)
} else {
glog.V(0).Infoln("Failed to assign", vid, "to", servers, "error", err)
return fmt.Errorf("Failed to assign %s: %s", vid.String(), err.Error())
}
}
return nil
}