git.scottworley.com Git - reliable-chat/blob - server/server.go

   1 /*  reliable-chat - multipath chat
   2  *  Copyright (C) 2012  Scott Worley <sworley@chkno.net>
   3  *
   4  *  This program is free software: you can redistribute it and/or modify
   5  *  it under the terms of the GNU Affero General Public License as
   6  *  published by the Free Software Foundation, either version 3 of the
   7  *  License, or (at your option) any later version.
   8  *
   9  *  This program is distributed in the hope that it will be useful,
  10  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  *  GNU Affero General Public License for more details.
  13  *
  14  *  You should have received a copy of the GNU Affero General Public License
  15  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 package main
  19
  20 import "container/list"
  21 import "encoding/json"
  22 import "expvar"
  23 import "flag"
  24 import "log"
  25 import "net/http"
  26 import "strconv"
  27 import "time"
  28
  29 var port = flag.Int("port", 21059, "Port to listen on")
  30 var localaddress = flag.String("localaddress", "", "Local address to bind to")
  31 var max_messages = flag.Int("maxmessages", 1000, "Maximum number of messages to retain")
  32
  33 var speak_count = expvar.NewInt("speak_count")
  34 var fetch_count = expvar.NewInt("fetch_count")
  35 var fetch_wait_count = expvar.NewInt("fetch_wait_count")
  36 var fetch_wake_count = expvar.NewInt("fetch_wake_count")
  37 var drop_due_to_limit_count = expvar.NewInt("drop_due_to_limit_count")
  38
  39 type Message struct {
  40         Time time.Time
  41         ID   string
  42         Text string
  43 }
  44
  45 type StoreRequest struct {
  46         StartTime time.Time
  47         Messages  chan<- []Message
  48 }
  49
  50 type Store struct {
  51         Add chan *Message
  52         Get chan *StoreRequest
  53 }
  54
  55 // TODO: Monotonic clock
  56
  57 func manage_store(store Store) {
  58         messages := list.New()
  59         message_count := 0
  60         waiting := list.New()
  61 main:
  62         for {
  63                 select {
  64                 case new_message, ok := <-store.Add:
  65                         if !ok {
  66                                 break main
  67                         }
  68                         speak_count.Add(1)
  69                         for waiter := waiting.Front(); waiter != nil; waiter = waiter.Next() {
  70                                 waiter.Value.(*StoreRequest).Messages <- []Message{*new_message}
  71                                 close(waiter.Value.(*StoreRequest).Messages)
  72                                 fetch_wake_count.Add(1)
  73                         }
  74                         waiting.Init()
  75                         messages.PushBack(new_message)
  76                         if message_count < *max_messages {
  77                                 message_count++
  78                         } else {
  79                                 messages.Remove(messages.Front())
  80                                 drop_due_to_limit_count.Add(1)
  81                         }
  82                 case request, ok := <-store.Get:
  83                         if !ok {
  84                                 break main
  85                         }
  86                         fetch_count.Add(1)
  87                         if messages.Back() == nil || !request.StartTime.Before(messages.Back().Value.(*Message).Time) {
  88                                 waiting.PushBack(request)
  89                                 fetch_wait_count.Add(1)
  90                         } else {
  91                                 start := messages.Back()
  92                                 response_size := 1
  93                                 if messages.Front().Value.(*Message).Time.After(request.StartTime) {
  94                                         start = messages.Front()
  95                                         response_size = message_count
  96                                 } else {
  97                                         for start.Prev().Value.(*Message).Time.After(request.StartTime) {
  98                                                 start = start.Prev()
  99                                                 response_size++
 100                                         }
 101                                 }
 102                                 response_messages := make([]Message, 0, response_size)
 103                                 for m := start; m != nil; m = m.Next() {
 104                                         response_messages = append(response_messages, *m.Value.(*Message))
 105                                 }
 106                                 request.Messages <- response_messages
 107                         }
 108                 }
 109         }
 110 }
 111
 112 func start_store() Store {
 113         store := Store{make(chan *Message, 20), make(chan *StoreRequest, 20)}
 114         go manage_store(store)
 115         return store
 116 }
 117
 118 const robots_txt = `User-agent: *
 119 Disallow: /
 120 `
 121
 122 func start_server(store Store) {
 123         http.HandleFunc("/fetch", func(w http.ResponseWriter, r *http.Request) {
 124                 var since time.Time
 125                 url_since := r.FormValue("since")
 126                 if url_since != "" {
 127                         err := json.Unmarshal([]byte(url_since), &since)
 128                         if err != nil {
 129                                 log.Print("fetch: parse since: ", err)
 130                                 w.WriteHeader(http.StatusBadRequest)
 131                                 w.Write([]byte("Could not parse since as date"))
 132                                 return
 133                         }
 134                 }
 135                 messages_from_store := make(chan []Message, 1)
 136                 store.Get <- &StoreRequest{since, messages_from_store}
 137
 138                 json_encoded, err := json.Marshal(<-messages_from_store)
 139                 if err != nil {
 140                         log.Print("json encode: ", err)
 141                         w.WriteHeader(http.StatusInternalServerError)
 142                         return
 143                 }
 144                 w.Header().Add("Content-Type", "application/json")
 145                 w.Header().Add("Access-Control-Allow-Origin", "*")
 146                 w.Write(json_encoded)
 147         })
 148
 149         http.HandleFunc("/speak", func(w http.ResponseWriter, r *http.Request) {
 150                 store.Add <- &Message{
 151                         time.Now(),
 152                         r.FormValue("id"),
 153                         r.FormValue("text")}
 154         })
 155
 156         http.HandleFunc("/robots.txt", func(w http.ResponseWriter, r *http.Request) {
 157                 w.Write([]byte(robots_txt));
 158         })
 159
 160         log.Fatal(http.ListenAndServe(*localaddress+":"+strconv.Itoa(*port), nil))
 161 }
 162
 163 func main() {
 164         flag.Parse()
 165         store := start_store()
 166         start_server(store)
 167 }