add support for pubsub
This commit is contained in:
teizz
69
src/broadcast.go
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69
src/broadcast.go
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@@ -0,0 +1,69 @@
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package main
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import (
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"io"
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)
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type broadcastWriter struct {
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writers []io.Writer
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}
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func (t *broadcastWriter) Close() (err error) {
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for i := 0; i < len(t.writers); i++ {
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if w, ok := t.writers[i].(io.WriteCloser); ok {
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if e := w.Close(); e != nil {
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err = e
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}
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}
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}
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return
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}
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func (t *broadcastWriter) Write(p []byte) (n int, err error) {
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for i := 0; i < len(t.writers); i++ {
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n, err = t.writers[i].Write(p)
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if err == nil && n != len(p) {
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err = io.ErrShortWrite
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}
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if err != nil {
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// if not at the end, move last to here and redo this
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if i < len(t.writers)-1 {
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// close the writer if it implements WriteCloser
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if w, ok := t.writers[i].(io.WriteCloser); ok {
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defer w.Close()
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}
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t.writers[i] = t.writers[len(t.writers)-1]
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i = i - 1
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}
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// always shorten list by one to drop the last one
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t.writers = t.writers[:len(t.writers)-1]
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}
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}
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if len(t.writers) <= 0 {
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return 0, err
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}
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return len(p), nil
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}
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// BroadcastWriter creates a writer that duplicates its writes to all the
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// provided writers, similar to the Unix tee(1) command.
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//
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// Each write is written to each listed writer, one at a time.
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// If a listed writer returns an error, that overall write operation
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// continues and the offending writer is dropped from the list.
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//
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// Only if all writers are dropped, the last error is returned at the end.
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func BroadcastWriter(writers ...io.Writer) io.WriteCloser {
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allWriters := make([]io.Writer, 0, len(writers))
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for _, w := range writers {
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if bw, ok := w.(*broadcastWriter); ok {
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allWriters = append(allWriters, bw.writers...)
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} else {
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allWriters = append(allWriters, w)
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}
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}
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return &broadcastWriter{allWriters}
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}
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43
src/get.go
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43
src/get.go
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@@ -0,0 +1,43 @@
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package main
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import (
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"io"
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"log"
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"net/http"
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"sync/atomic"
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)
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func handleGet(pathID string, w http.ResponseWriter, r *http.Request) {
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queue := &Queue{ch: make(chan Transfer)}
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if p, loaded := paths.LoadOrStore(pathID, queue); loaded {
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queue = p.(*Queue)
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debug("%s [GET] Loads path", pathID)
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} else {
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debug("%s [GET] Created path", pathID)
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}
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atomic.AddInt32(&queue.gets, 1)
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select {
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case transfer := <-queue.ch:
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debug("%s [GET] Reads from path", pathID)
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if transfer.contentlength != "" {
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w.Header().Set("Content-Length", transfer.contentlength)
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}
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_, err := io.Copy(w, transfer.reader)
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if err != nil {
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transfer.reader.Close()
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}
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debug("%s [GET] Sends done", pathID)
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close(transfer.done)
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case <-r.Context().Done():
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debug("%s [GET] Cancels path", pathID)
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}
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if atomic.AddInt32(&queue.gets, -1) <= 0 {
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if atomic.LoadInt32(&queue.posts) <= 0 {
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paths.Delete(pathID)
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debug("%s [GET] Removes path", pathID)
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}
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}
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log.Printf("%s [GET] Finishes", pathID)
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}
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98
src/main.go
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98
src/main.go
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@@ -0,0 +1,98 @@
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package main
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import (
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"io"
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"log"
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"net/http"
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"sync"
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)
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var (
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// variables to set during build-time
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debugging = ""
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version = "0.0-undefined"
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buildtime = "0000-00-00T00:00:00+0000"
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// actual business end of the device
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paths = &sync.Map{}
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)
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// Transfer holds a single tranferable connection to be read
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type Transfer struct {
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reader io.ReadCloser
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done chan struct{}
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contentlength string
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}
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// NewTransfer returns a ready to use Transfer and it's writer
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func NewTransfer(contentlength string) (transfer Transfer, writer io.WriteCloser) {
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var reader io.ReadCloser
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reader, writer = io.Pipe()
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transfer = Transfer{
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reader: reader.(io.ReadCloser),
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contentlength: contentlength,
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done: make(chan struct{}),
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}
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return
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}
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// Queue is where posts and gets can exchange transfers
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type Queue struct {
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ch chan Transfer
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posts int32
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gets int32
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}
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func pathHandler(w http.ResponseWriter, r *http.Request) {
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pathID := r.URL.Path
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if len(pathID) < 2 {
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w.WriteHeader(400)
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w.Write([]byte("path to short"))
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return
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}
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if r.Method == "GET" {
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log.Printf("%s [GET] Connected", pathID)
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handleGet(pathID, w, r)
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} else {
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log.Printf("%s [POST] Connected", pathID)
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if h := r.Header.Get("X-Pathway"); h == "pubsub" {
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debug("%s [PUBSUB] Upgrade POST to PUBSUB", pathID)
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handlePubSub(pathID, r)
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} else {
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handlePost(pathID, r)
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}
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}
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}
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func okHandler(w http.ResponseWriter, r *http.Request) {
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w.WriteHeader(http.StatusOK)
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w.Write([]byte("ok"))
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}
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func emptyHandler(w http.ResponseWriter, r *http.Request) {
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w.WriteHeader(http.StatusOK)
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}
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func main() {
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log.Printf("pathway version:%s buildtime:%s", version, buildtime)
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http.HandleFunc("/health", okHandler)
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http.HandleFunc("/favicon.ico", emptyHandler)
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http.HandleFunc("/robots.txt", emptyHandler)
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http.HandleFunc("/", pathHandler)
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err := http.ListenAndServe(":8080", nil)
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if err != nil {
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log.Println(err)
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}
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}
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func debug(msg string, args ...interface{}) {
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if len(debugging) > 0 {
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log.Printf(msg, args...)
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}
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}
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103
src/post.go
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103
src/post.go
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@@ -0,0 +1,103 @@
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package main
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import (
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"io"
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"log"
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"net/http"
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"sync/atomic"
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)
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func handlePubSub(pathID string, r *http.Request) {
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var queue *Queue
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if p, loaded := paths.Load(pathID); loaded {
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queue = p.(*Queue)
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debug("%s [PUBSUB] Loads path", pathID)
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} else {
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debug("%s [PUBSUB] No subs for path", pathID)
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return
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}
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if atomic.AddInt32(&queue.posts, 1) > 1 {
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debug("%s [PUBSUB] Path already has posts", pathID)
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atomic.AddInt32(&queue.posts, -1)
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return
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}
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var masterWriter io.WriteCloser
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var done bool
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for !done {
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transfer, writer := NewTransfer(r.Header.Get("Content-Length"))
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select {
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case queue.ch <- transfer:
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debug("%s [PUBSUB] Adds sub to pub", pathID)
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if masterWriter == nil {
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masterWriter = BroadcastWriter(writer)
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} else {
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masterWriter = BroadcastWriter(masterWriter, writer)
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}
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default:
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debug("%s [PUBSUB] Saturated path", pathID)
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done = true
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}
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}
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n, err := io.Copy(masterWriter, r.Body)
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debug("%s [PUBSUB] Sends %d bytes", pathID, n)
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if err != nil {
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debug("%s [PUBSUB] Has error: %s", pathID, err.Error())
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}
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masterWriter.Close()
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r.Body.Close()
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if atomic.AddInt32(&queue.posts, -1) <= 0 {
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if atomic.LoadInt32(&queue.gets) <= 0 {
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paths.Delete(pathID)
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close(queue.ch)
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debug("%s [PUBSUB] Removes path", pathID)
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}
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}
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log.Printf("%s [PUBSUB] Finishes", pathID)
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}
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func handlePost(pathID string, r *http.Request) {
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queue := &Queue{ch: make(chan Transfer)}
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if p, loaded := paths.LoadOrStore(pathID, queue); loaded {
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queue = p.(*Queue)
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debug("%s [POST] Loads path", pathID)
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} else {
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debug("%s [POST] Creates path", pathID)
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}
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atomic.AddInt32(&queue.posts, 1)
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transfer, writer := NewTransfer(r.Header.Get("Content-Length"))
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go func() {
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n, err := io.Copy(writer, r.Body)
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debug("%s [POST] Sends %d bytes", pathID, n)
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if err != nil {
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debug("%s [POST] Has error: %s", pathID, err.Error())
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}
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writer.Close()
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r.Body.Close()
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}()
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select {
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case queue.ch <- transfer:
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debug("%s [POST] Writes to path", pathID)
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case <-r.Context().Done():
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debug("%s [POST] Cancels path", pathID)
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close(transfer.done)
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}
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debug("%s [POST] Waits for done", pathID)
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<-transfer.done
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if atomic.AddInt32(&queue.posts, -1) <= 0 {
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if atomic.LoadInt32(&queue.gets) <= 0 {
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paths.Delete(pathID)
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close(queue.ch)
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debug("%s [POST] Removes path", pathID)
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}
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}
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log.Printf("%s [POST] Finishes", pathID)
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}
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