git.sesse.net Git - remoteglot/blob - www/serve-analysis.js

   1 // node.js version of analysis.pl; hopefully scales a bit better
   2 // for this specific kind of task.
   3
   4 // Modules.
   5 var http = require('http');
   6 var fs = require('fs');
   7 var url = require('url');
   8 var querystring = require('querystring');
   9 var path = require('path');
  10 var zlib = require('zlib');
  11
  12 // Constants.
  13 var json_filename = '/srv/analysis.sesse.net/www/analysis.json';
  14
  15 // The current contents of the file to hand out, and its last modified time.
  16 var json_contents = undefined;
  17 var json_contents_gz = undefined;
  18 var json_last_modified = undefined;
  19
  20 // The list of clients that are waiting for new data to show up.
  21 // Uniquely keyed by request_id so that we can take them out of
  22 // the queue if they close the socket.
  23 var sleeping_clients = {};
  24 var request_id = 0;
  25
  26 // List of when clients were last seen, keyed by their unique ID.
  27 // Used to show a viewer count to the user.
  28 var last_seen_clients = {};
  29
  30 // The timer used to touch the file every 30 seconds if nobody
  31 // else does it for us. This makes sure we don't have clients
  32 // hanging indefinitely (which might have them return errors).
  33 var touch_timer = undefined;
  34
  35 var reread_file = function(event, filename) {
  36         if (filename != path.basename(json_filename)) {
  37                 return;
  38         }
  39         console.log("Rereading " + json_filename);
  40         fs.open(json_filename, 'r+', function(err, fd) {
  41                 if (err) throw err;
  42                 fs.fstat(fd, function(err, st) {
  43                         if (err) throw err;
  44                         var buffer = new Buffer(1048576);
  45                         fs.read(fd, buffer, 0, 1048576, 0, function(err, bytesRead, buffer) {
  46                                 if (err) throw err;
  47                                 fs.close(fd, function() {
  48                                         var new_json_contents = buffer.toString('utf8', 0, bytesRead);
  49                                         zlib.gzip(new_json_contents, function(err, buffer) {
  50                                                 if (err) throw err;
  51                                                 json_contents = new_json_contents;
  52                                                 json_contents_gz = buffer;
  53                                                 json_last_modified = st.mtime.getTime();
  54                                                 possibly_wakeup_clients();
  55                                         });
  56                                 });
  57                         });
  58                 });
  59         });
  60
  61         if (touch_timer !== undefined) {
  62                 clearTimeout(touch_timer);
  63         }
  64         touch_timer = setTimeout(function() {
  65                 console.log("Touching analysis.json due to no other activity");
  66                 var now = Date.now() / 1000;
  67                 fs.utimes(json_filename, now, now);
  68         }, 30000);
  69 }
  70 var possibly_wakeup_clients = function() {
  71         var num_viewers = count_viewers();
  72         for (var i in sleeping_clients) {
  73                 mark_recently_seen(sleeping_clients[i].unique);
  74                 send_json(sleeping_clients[i].response,
  75                           sleeping_clients[i].accept_gzip,
  76                           num_viewers);
  77         }
  78         sleeping_clients = {};
  79 }
  80 var send_404 = function(response) {
  81         response.writeHead(404, {
  82                 'Content-Type': 'text/plain',
  83         });
  84         response.write('Something went wrong. Sorry.');
  85         response.end();
  86 }
  87 var send_json = function(response, accept_gzip, num_viewers) {
  88         var headers = {
  89                 'Content-Type': 'text/json',
  90                 'X-Remoteglot-Last-Modified': json_last_modified,
  91                 'X-Remoteglot-Num-Viewers': num_viewers,
  92                 'Access-Control-Allow-Origin': 'http://analysis.sesse.net',
  93                 'Access-Control-Expose-Headers': 'X-Remoteglot-Last-Modified, X-Remoteglot-Num-Viewers',
  94                 'Expires': 'Mon, 01 Jan 1970 00:00:00 UTC',
  95         };
  96
  97         if (accept_gzip) {
  98                 headers['Content-Encoding'] = 'gzip';
  99                 response.writeHead(200, headers);
 100                 response.write(json_contents_gz);
 101         } else {
 102                 response.writeHead(200, headers);
 103                 response.write(json_contents);
 104         }
 105         response.end();
 106 }
 107 var mark_recently_seen = function(unique) {
 108         if (unique) {
 109                 last_seen_clients[unique] = (new Date).getTime();
 110         }
 111 }
 112 var count_viewers = function() {
 113         var now = (new Date).getTime();
 114
 115         // Go through and remove old viewers, and count them at the same time.
 116         var new_last_seen_clients = {};
 117         var num_viewers = 0;
 118         for (var unique in last_seen_clients) {
 119                 if (now - last_seen_clients[unique] < 5000) {
 120                         ++num_viewers;
 121                         new_last_seen_clients[unique] = last_seen_clients[unique];
 122                 }
 123         }
 124
 125         // Also add sleeping clients that we would otherwise assume timed out.
 126         for (var request_id in sleeping_clients) {
 127                 var unique = sleeping_clients[request_id].unique;
 128                 if (unique && !(unique in new_last_seen_clients)) {
 129                         ++num_viewers;
 130                 }
 131         }
 132
 133         last_seen_clients = new_last_seen_clients;
 134         return num_viewers;
 135 }
 136
 137 // Set up a watcher to catch changes to the file, then do an initial read
 138 // to make sure we have a copy.
 139 fs.watch(path.dirname(json_filename), reread_file);
 140 reread_file(null, path.basename(json_filename));
 141
 142 var server = http.createServer();
 143 server.on('request', function(request, response) {
 144         var u = url.parse(request.url, true);
 145         var ims = (u.query)['ims'];
 146         var unique = (u.query)['unique'];
 147
 148         console.log((new Date).getTime()*1e-3 + " " + request.url);
 149
 150         if (u.pathname !== '/analysis.pl') {
 151                 // This is not the request you are looking for.
 152                 send_404(response);
 153                 return;
 154         }
 155
 156         mark_recently_seen(unique);
 157
 158         var accept_encoding = request.headers['accept-encoding'];
 159         var accept_gzip;
 160         if (accept_encoding !== undefined && accept_encoding.match(/\bgzip\b/)) {
 161                 accept_gzip = true;
 162         } else {
 163                 accept_gzip = false;
 164         }
 165
 166         // If we already have something newer than what the user has,
 167         // just send it out and be done with it.
 168         if (json_last_modified !== undefined && (!ims || json_last_modified > ims)) {
 169                 send_json(response, accept_gzip, count_viewers());
 170                 return;
 171         }
 172
 173         // OK, so we need to hang until we have something newer.
 174         // Put the user on the wait list.
 175         var client = {};
 176         client.response = response;
 177         client.request_id = request_id;
 178         client.accept_gzip = accept_gzip;
 179         client.unique = unique;
 180         sleeping_clients[request_id++] = client;
 181
 182         request.socket.client = client;
 183 });
 184 server.on('connection', function(socket) {
 185         socket.on('close', function() {
 186                 var client = socket.client;
 187                 if (client) {
 188                         mark_recently_seen(client.unique);
 189                         delete sleeping_clients[client.request_id];
 190                 }
 191         });
 192 });
 193 server.listen(5000);