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 start_time = expvar.NewInt("start_time")
  34 var speak_count = expvar.NewInt("speak_count")
  35 var fetch_count = expvar.NewInt("fetch_count")
  36 var fetch_wait_count = expvar.NewInt("fetch_wait_count")
  37 var fetch_wake_count = expvar.NewInt("fetch_wake_count")
  38 var drop_due_to_limit_count = expvar.NewInt("drop_due_to_limit_count")
  39
  40 type Message struct {
  41         Time time.Time
  42         ID   string
  43         Text string
  44 }
  45
  46 type StoreRequest struct {
  47         StartTime time.Time
  48         Messages  chan<- []Message
  49 }
  50
  51 type Store struct {
  52         Add chan *Message
  53         Get chan *StoreRequest
  54 }
  55
  56 var monotonic_clock chan chan time.Time
  57
  58 const minimum_clock_increment = time.Millisecond
  59
  60 func start_clock() {
  61         internal_monotonic_clock := make(chan chan time.Time, 1)
  62         go func() {
  63                 last_time := time.Now()
  64         main:
  65                 for {
  66                         select {
  67                         case request, ok := <-internal_monotonic_clock:
  68                                 if !ok {
  69                                         break main
  70                                 }
  71                                 earliest_acceptable_time := last_time.Add(minimum_clock_increment)
  72                                 current_time := time.Now()
  73                                 if current_time.Before(earliest_acceptable_time) {
  74                                         current_time = earliest_acceptable_time
  75                                 }
  76                                 request <- current_time
  77                                 last_time = current_time
  78                         }
  79                 }
  80         }()
  81         monotonic_clock = internal_monotonic_clock
  82 }
  83
  84 func now() time.Time {
  85         c := make(chan time.Time, 0)
  86         monotonic_clock <- c
  87         return <-c
  88 }
  89
  90 func manage_store(store Store) {
  91         messages := list.New()
  92         message_count := 0
  93         waiting := list.New()
  94 main:
  95         for {
  96                 select {
  97                 case new_message, ok := <-store.Add:
  98                         if !ok {
  99                                 break main
 100                         }
 101                         speak_count.Add(1)
 102                         for waiter := waiting.Front(); waiter != nil; waiter = waiter.Next() {
 103                                 waiter.Value.(*StoreRequest).Messages <- []Message{*new_message}
 104                                 close(waiter.Value.(*StoreRequest).Messages)
 105                                 fetch_wake_count.Add(1)
 106                         }
 107                         waiting.Init()
 108                         messages.PushBack(new_message)
 109                         if message_count < *max_messages {
 110                                 message_count++
 111                         } else {
 112                                 messages.Remove(messages.Front())
 113                                 drop_due_to_limit_count.Add(1)
 114                         }
 115                 case request, ok := <-store.Get:
 116                         if !ok {
 117                                 break main
 118                         }
 119                         fetch_count.Add(1)
 120                         if messages.Back() == nil || !request.StartTime.Before(messages.Back().Value.(*Message).Time) {
 121                                 waiting.PushBack(request)
 122                                 fetch_wait_count.Add(1)
 123                         } else {
 124                                 start := messages.Back()
 125                                 response_size := 1
 126                                 if messages.Front().Value.(*Message).Time.After(request.StartTime) {
 127                                         start = messages.Front()
 128                                         response_size = message_count
 129                                 } else {
 130                                         for start.Prev().Value.(*Message).Time.After(request.StartTime) {
 131                                                 start = start.Prev()
 132                                                 response_size++
 133                                         }
 134                                 }
 135                                 response_messages := make([]Message, 0, response_size)
 136                                 for m := start; m != nil; m = m.Next() {
 137                                         response_messages = append(response_messages, *m.Value.(*Message))
 138                                 }
 139                                 request.Messages <- response_messages
 140                         }
 141                 }
 142         }
 143 }
 144
 145 func start_store() Store {
 146         store := Store{make(chan *Message, 20), make(chan *StoreRequest, 20)}
 147         go manage_store(store)
 148         return store
 149 }
 150
 151 const robots_txt = `User-agent: *
 152 Disallow: /
 153 `
 154
 155 func start_server(store Store) {
 156         http.HandleFunc("/fetch", func(w http.ResponseWriter, r *http.Request) {
 157                 var since time.Time
 158                 url_since := r.FormValue("since")
 159                 if url_since != "" {
 160                         err := json.Unmarshal([]byte(url_since), &since)
 161                         if err != nil {
 162                                 log.Print("fetch: parse since: ", err)
 163                                 w.WriteHeader(http.StatusBadRequest)
 164                                 w.Write([]byte("Could not parse since as date"))
 165                                 return
 166                         }
 167                 }
 168                 messages_from_store := make(chan []Message, 1)
 169                 store.Get <- &StoreRequest{since, messages_from_store}
 170
 171                 json_encoded, err := json.Marshal(<-messages_from_store)
 172                 if err != nil {
 173                         log.Print("json encode: ", err)
 174                         w.WriteHeader(http.StatusInternalServerError)
 175                         return
 176                 }
 177                 w.Header().Add("Content-Type", "application/json")
 178                 w.Header().Add("Access-Control-Allow-Origin", "*")
 179                 w.Write(json_encoded)
 180         })
 181
 182         http.HandleFunc("/speak", func(w http.ResponseWriter, r *http.Request) {
 183                 store.Add <- &Message{
 184                         now(),
 185                         r.FormValue("id"),
 186                         r.FormValue("text")}
 187                 w.Header().Add("Access-Control-Allow-Origin", "*")
 188         })
 189
 190         http.HandleFunc("/robots.txt", func(w http.ResponseWriter, r *http.Request) {
 191                 w.Write([]byte(robots_txt))
 192         })
 193
 194         log.Fatal(http.ListenAndServe(*localaddress+":"+strconv.Itoa(*port), nil))
 195 }
 196
 197 func main() {
 198         flag.Parse()
 199         start_clock()
 200         start_time.Set(now().UnixNano())
 201         store := start_store()
 202         start_server(store)
 203 }