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 // and their associated timers. Uniquely keyed by request_id
  22 // so that we can take them out of the queue if they time out.
  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 var reread_file = function(event, filename) {
  31         if (filename != path.basename(json_filename)) {
  32                 return;
  33         }
  34         console.log("Rereading " + json_filename);
  35         fs.open(json_filename, 'r+', function(err, fd) {
  36                 if (err) throw err;
  37                 fs.fstat(fd, function(err, st) {
  38                         if (err) throw err;
  39                         var buffer = new Buffer(1048576);
  40                         fs.read(fd, buffer, 0, 1048576, 0, function(err, bytesRead, buffer) {
  41                                 if (err) throw err;
  42                                 fs.close(fd, function() {
  43                                         var new_json_contents = buffer.toString('utf8', 0, bytesRead);
  44                                         zlib.gzip(new_json_contents, function(err, buffer) {
  45                                                 if (err) throw err;
  46                                                 json_contents = new_json_contents;
  47                                                 json_contents_gz = buffer;
  48                                                 json_last_modified = st.mtime.getTime();
  49                                                 possibly_wakeup_clients();
  50                                         });
  51                                 });
  52                         });
  53                 });
  54         });
  55 }
  56 var possibly_wakeup_clients = function() {
  57         var num_viewers = count_viewers();
  58         for (var i in sleeping_clients) {
  59                 clearTimeout(sleeping_clients[i].timer);
  60                 mark_recently_seen(sleeping_clients[i].unique);
  61                 send_json(sleeping_clients[i].response,
  62                           sleeping_clients[i].accept_gzip,
  63                           num_viewers);
  64         }
  65         sleeping_clients = {};
  66 }
  67 var send_404 = function(response) {
  68         response.writeHead(404, {
  69                 'Content-Type': 'text/plain',
  70         });
  71         response.write('Something went wrong. Sorry.');
  72         response.end();
  73 }
  74 var send_json = function(response, accept_gzip, num_viewers) {
  75         var headers = {
  76                 'Content-Type': 'text/json',
  77                 'X-Remoteglot-Last-Modified': json_last_modified,
  78                 'X-Remoteglot-Num-Viewers': num_viewers,
  79                 'Access-Control-Allow-Origin': 'http://analysis.sesse.net',
  80                 'Access-Control-Expose-Headers': 'X-Remoteglot-Last-Modified, X-Remoteglot-Num-Viewers',
  81                 'Expires': 'Mon, 01 Jan 1970 00:00:00 UTC',
  82         };
  83
  84         if (accept_gzip) {
  85                 headers['Content-Encoding'] = 'gzip';
  86                 response.writeHead(200, headers);
  87                 response.write(json_contents_gz);
  88         } else {
  89                 response.writeHead(200, headers);
  90                 response.write(json_contents);
  91         }
  92         response.end();
  93 }
  94 var timeout_client = function(client) {
  95         mark_recently_seen(client.unique);
  96         send_json(client.response, client.accept_gzip, count_viewers());
  97         delete sleeping_clients[client.request_id];
  98 }
  99 var mark_recently_seen = function(unique) {
 100         if (unique) {
 101                 last_seen_clients[unique] = (new Date).getTime();
 102         }
 103 }
 104 var count_viewers = function() {
 105         var now = (new Date).getTime();
 106
 107         // Go through and remove old viewers, and count them at the same time.
 108         var new_last_seen_clients = {};
 109         var num_viewers = 0;
 110         for (var unique in last_seen_clients) {
 111                 if (now - last_seen_clients[unique] < 5000) {
 112                         ++num_viewers;
 113                         new_last_seen_clients[unique] = last_seen_clients[unique];
 114                 }
 115         }
 116
 117         // Also add sleeping clients that we would otherwise assume timed out.
 118         for (var request_id in sleeping_clients) {
 119                 var unique = sleeping_clients[request_id].unique;
 120                 if (unique && !(unique in new_last_seen_clients)) {
 121                         ++num_viewers;
 122                 }
 123         }
 124
 125         last_seen_clients = new_last_seen_clients;
 126         return num_viewers;
 127 }
 128
 129 // Set up a watcher to catch changes to the file, then do an initial read
 130 // to make sure we have a copy.
 131 fs.watch(path.dirname(json_filename), reread_file);
 132 reread_file(null, path.basename(json_filename));
 133
 134 var server = http.createServer();
 135 server.on('request', function(request, response) {
 136         var u = url.parse(request.url, true);
 137         var ims = (u.query)['ims'];
 138         var unique = (u.query)['unique'];
 139
 140         console.log((new Date).getTime()*1e-3 + " " + request.url);
 141
 142         if (u.pathname !== '/analysis.pl') {
 143                 // This is not the request you are looking for.
 144                 send_404(response);
 145                 return;
 146         }
 147
 148         mark_recently_seen(unique);
 149
 150         var accept_encoding = request.headers['accept-encoding'];
 151         var accept_gzip;
 152         if (accept_encoding !== undefined && accept_encoding.match(/\bgzip\b/)) {
 153                 accept_gzip = true;
 154         } else {
 155                 accept_gzip = false;
 156         }
 157
 158         // If we already have something newer than what the user has,
 159         // just send it out and be done with it.
 160         if (json_last_modified !== undefined && (!ims || json_last_modified > ims)) {
 161                 send_json(response, accept_gzip, count_viewers());
 162                 return;
 163         }
 164
 165         // OK, so we need to hang until we have something newer.
 166         // Put the user on the wait list; if we don't get anything
 167         // in 30 seconds, though, we'll send something anyway.
 168         var client = {};
 169         client.response = response;
 170         client.timer = setTimeout(function() { timeout_client(client); }, 30000);
 171         client.request_id = request_id;
 172         client.accept_gzip = accept_gzip;
 173         client.unique = unique;
 174         sleeping_clients[request_id++] = client;
 175
 176         request.socket.client = client;
 177 });
 178 server.on('connection', function(socket) {
 179         socket.on('close', function() {
 180                 var client = socket.client;
 181                 if (client) {
 182                         mark_recently_seen(client.unique);
 183                         delete sleeping_clients[client.request_id];
 184                 }
 185         });
 186 });
 187 server.listen(5000);