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master.go
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master.go
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package main
import (
"encoding/json"
"fmt"
"log"
"math/rand"
"net/http"
"strconv"
"strings"
)
type RegisterChunkserverRequest struct {
Url string `json:"url"`
}
type RegisterChunkserverResponse struct {
}
type UploadInitRequest struct {
FileName string `json:"fileName"`
FileSize uint64 `json:"fileSize"`
}
type UploadInitResponse struct {
Identifier string `json:"identifier"`
ChunkSize uint64 `json:"chunkSize"`
NumberOfChunks uint64 `json:"numberOfChunks"`
Chunkservers []string `json:"chunkservers"`
}
type ChunkUploadSuccessRequest struct {
ChunkIdentifier string `json:"chunkIdentifier"`
Chunkserver string `json:"chunkserver"`
}
type GetResponse struct {
FileName string
Locations []string
}
type FileMetadata struct {
FileName string
FileSize uint64
NumberOfChunks uint64
Replicas [][]string
}
type MasterServer struct {
Port string
ChunkSize uint64
ChunkserverUrls map[string]struct{}
Files map[string]FileMetadata
}
func NewMasterServer(port string, chunkSize uint64) *MasterServer {
return &MasterServer{port, chunkSize, make(map[string]struct{}), make(map[string]FileMetadata)}
}
func (master *MasterServer) run() error {
master.registerUploadEndpoint()
master.registerGetEndpoint()
master.registerReportChunkUploadSuccessEndpoint()
master.registerRegisterChunkserverEndpoint()
if err := http.ListenAndServe(":"+master.Port, nil); err != nil {
log.Fatal(err)
}
return nil
}
func (master *MasterServer) registerUploadEndpoint() {
http.HandleFunc("/upload", loggingMiddleware(func(w http.ResponseWriter, r *http.Request) {
var uploadReq UploadInitRequest
if err := json.NewDecoder(r.Body).Decode(&uploadReq); err != nil {
http.Error(w, "error parsing request body", 400)
return
}
if len(master.ChunkserverUrls) == 0 {
http.Error(w, "no chunkserver available", 500)
return
}
fileIdentifier := getIdentifierFromFilename(uploadReq.FileName)
numberOfChunks := calcNumberOfChunks(uploadReq.FileSize, master.ChunkSize)
// urls := reflect.ValueOf(master.ChunkserverUrls).MapKeys()
// randomChunkserver := urls[rand.Intn(len(urls))].String()
chunkservers := make([]string, 0, len(master.ChunkserverUrls))
for k := range master.ChunkserverUrls {
chunkservers = append(chunkservers, k)
}
master.Files[fileIdentifier] = FileMetadata{uploadReq.FileName, uploadReq.FileSize, numberOfChunks, make([][]string, numberOfChunks)}
response := UploadInitResponse{
Identifier: fileIdentifier,
ChunkSize: master.ChunkSize,
NumberOfChunks: numberOfChunks,
Chunkservers: chunkservers,
}
json.NewEncoder(w).Encode(response)
}))
}
func (master *MasterServer) registerGetEndpoint() {
http.HandleFunc("/get", loggingMiddleware(func(w http.ResponseWriter, r *http.Request) {
fileIdentifier := r.URL.Query()["id"][0]
metadata, ok := master.Files[fileIdentifier]
if !ok {
http.Error(w, fmt.Sprintf("file with identifier '%v' not found", fileIdentifier), http.StatusNotFound)
return
}
locations := make([]string, metadata.NumberOfChunks)
for i, v := range metadata.Replicas {
if len(v) == 0 {
http.Error(w, "file exists but not all chunks are currently available", http.StatusNotFound)
return
}
// for now we pick a random chunkserver for each chunk.
// GFS picks the chunkserver that is closest to the client and does bulk requests
locations[i] = metadata.Replicas[i][rand.Intn(len(metadata.Replicas[i]))]
}
response := GetResponse{
FileName: metadata.FileName,
Locations: locations,
}
json.NewEncoder(w).Encode(response)
}))
}
func (master *MasterServer) registerReportChunkUploadSuccessEndpoint() {
http.HandleFunc("/uploadSuccessful", loggingMiddleware(func(w http.ResponseWriter, r *http.Request) {
var uploadSuccessReq ChunkUploadSuccessRequest
if err := json.NewDecoder(r.Body).Decode(&uploadSuccessReq); err != nil {
http.Error(w, "error parsing request body", 400)
return
}
parts := strings.Split(uploadSuccessReq.ChunkIdentifier, "_")
fileIdentifier := parts[0]
chunkIndex, err := strconv.Atoi(parts[1])
if err != nil {
http.Error(w, fmt.Sprintf("error parsing chunk index: %v", err), http.StatusBadRequest)
}
master.Files[fileIdentifier].Replicas[chunkIndex] = append(master.Files[fileIdentifier].Replicas[chunkIndex], uploadSuccessReq.Chunkserver)
}))
}
func (master *MasterServer) registerRegisterChunkserverEndpoint() {
http.HandleFunc("/chunkserver", loggingMiddleware(func(w http.ResponseWriter, r *http.Request) {
var registerReq RegisterChunkserverRequest
if err := json.NewDecoder(r.Body).Decode(®isterReq); err != nil {
http.Error(w, "error parsing request body", 400)
}
master.ChunkserverUrls[registerReq.Url] = struct{}{}
response := RegisterChunkserverResponse{}
json.NewEncoder(w).Encode(response)
}))
}