/
cstore.go
200 lines (178 loc) · 4.89 KB
/
cstore.go
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package main
import (
"fmt"
"http"
"http/httptest"
"io/ioutil"
"log"
"os"
"regexp"
"strings"
"sync"
"url"
)
var (
url_regexp = regexp.MustCompile("^/([0-9a-f]*)$")
)
// Our server state.
type handler struct {
locker sync.RWMutex // Must be held to access content.
content map[string][]byte // Maps SHA256 digest to content.
registry *Registry // Used to find server with content.
client *http.Client // Used for recursive calls.
}
// Safely store content in our hash table.
func (h *handler) setContent(digest string, content []byte) {
h.locker.Lock()
defer h.locker.Unlock()
h.content[digest] = content
}
// Store content in our hash table and let everybody know we have it.
func (h *handler) setContentAndRegister(digest string, content []byte) {
h.setContent(digest, content)
if err := h.registry.RegisterDigest(digest); err != nil {
log.Println("Unable to register", digest)
}
}
// Safely fetch content from our hash table. Return nil if we don't have
// any content for the specified digest.
func (h *handler) getContent(digest string) []byte {
h.locker.RLock()
defer h.locker.RUnlock()
return h.content[digest]
}
// Read and write content via HTTP.
func (h *handler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
log.Println(req.Method, req.URL.Path)
// Extract the SHA digest from our URL.
digest, err := parseUrlPath(req.URL.Path)
if err != nil {
w.WriteHeader(http.StatusForbidden)
fmt.Fprintln(w, err)
return
}
switch req.Method {
case "GET":
h.serveGET(digest, w, req)
case "PUT":
h.servePUT(digest, w, req)
default:
w.WriteHeader(http.StatusMethodNotAllowed)
}
}
// Parse a URL path. We expect all paths to be "/" followed by an SHA256
// sum. (We may add support for a bare "/" if we add POST support.)
func parseUrlPath(path string) (digest string, err os.Error) {
match := url_regexp.FindStringSubmatch(path)
if match == nil || len(match[1]) != 64 {
err = os.NewError("Invalid resource path")
return
}
digest = strings.ToLower(match[1])
return
}
// Attempt to fetch a stored blob.
func (h *handler) serveGET(digest string, w http.ResponseWriter, req *http.Request) {
content := h.getContent(digest)
if content == nil {
content = h.tryRecursiveGET(digest)
if content == nil {
w.WriteHeader(http.StatusNotFound)
return
}
}
if _, err := w.Write(content); err != nil {
log.Println("Error writing response:", err)
return
}
}
// Attempt to GET the specified digest from another server.
// TODO: Think hard about error conditions here.
func (h *handler) tryRecursiveGET(digest string) (content []byte) {
servers, err := h.registry.FindServers(digest)
if err != nil {
log.Println("Error checking registry:", err)
return nil
}
for _, server := range(servers) {
url := "http://" + server + "/" + digest
content, err = h.tryGET(url)
if err != nil {
log.Printf("Error fetching data:", err)
} else {
h.setContentAndRegister(digest, content)
return
}
}
return nil
}
// Try fetching a single URL.
func (h *handler) tryGET(url string) (content []byte, err os.Error) {
resp, err := h.client.Get(url)
if err != nil {
return
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
err = os.NewError("Error fetching data: " + resp.Status)
return
}
return ioutil.ReadAll(resp.Body)
}
// Attempt to store a new blob.
func (h *handler) servePUT(digest string, w http.ResponseWriter, req *http.Request) {
dr := NewDigestReader(req.Body)
content, err := ioutil.ReadAll(dr)
if err != nil {
w.WriteHeader(http.StatusInternalServerError)
fmt.Fprintln(w, "Could not read payload")
return
}
if digest != dr.Digest() {
w.WriteHeader(http.StatusBadRequest)
fmt.Fprintln(w, "SHA256 digest does not match content!")
return
}
h.setContentAndRegister(digest, content)
w.WriteHeader(http.StatusCreated)
}
func newHandler() *handler {
handler := new(handler)
handler.content = make(map[string][]byte)
handler.registry = NewRegistry()
handler.client = new(http.Client)
return handler
}
// Listen and serve on the specified interface and port. Does not return.
func ListenAndServe(addr string) {
handler := newHandler()
if err := handler.registry.RegisterThisServer(addr); err != nil {
log.Fatal("Can't register server with Redis:", err)
}
if err := http.ListenAndServe(addr, handler); err != nil {
log.Fatal("Can't start server:", err)
}
}
type TestServer struct {
handler *handler
server *httptest.Server
}
func (ts *TestServer) URL() string {
return ts.server.URL
}
func (ts *TestServer) Close() {
ts.handler.registry.UnregisterThisServer()
ts.server.Close()
}
// Create a new server for use in unit tests. When done, be sure to call
// Close().
func NewTestServer() *TestServer {
handler := newHandler()
server := httptest.NewServer(handler)
url, err := url.Parse(server.URL)
if err != nil {
panic(err)
}
handler.registry.RegisterThisServer(url.Host)
return &TestServer{handler: handler, server: server}
}