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
  10 // Constants.
  11 var json_filename = '/srv/analysis.sesse.net/www/analysis.json';
  12
  13 // The current contents of the file to hand out, and its last modified time.
  14 var json_contents = null;
  15 var json_last_modified = null;
  16
  17 // The list of clients that are waiting for new data to show up,
  18 // and their associated timers. Uniquely keyed by request_id
  19 // so that we can take them out of the queue if they time out.
  20 var sleeping_clients = {};
  21 var request_id = 0;
  22
  23 // List of when clients were last seen, keyed by their unique ID.
  24 // Used to show a viewer count to the user.
  25 var last_seen_clients = {};
  26
  27 var reread_file = function() {
  28         fs.open(json_filename, 'r+', function(err, fd) {
  29                 if (err) throw err;
  30                 fs.fstat(fd, function(err, st) {
  31                         if (err) throw err;
  32                         var buffer = new Buffer(1048576);
  33                         fs.read(fd, buffer, 0, 1048576, 0, function(err, bytesRead, buffer) {
  34                                 if (err) throw err;
  35                                 fs.close(fd, function() {
  36                                         json_contents = buffer.toString('utf8', 0, bytesRead);
  37                                         json_last_modified = st.mtime.getTime();
  38                                         possibly_wakeup_clients();
  39                                 });
  40                         });
  41                 });
  42         });
  43 }
  44 var possibly_wakeup_clients = function() {
  45         for (var i in sleeping_clients) {
  46                 clearTimeout(sleeping_clients[i].timer);
  47                 send_json(sleeping_clients[i].response);
  48         }
  49         sleeping_clients = {};
  50 }
  51 var send_404 = function(response) {
  52         response.writeHead(404, {
  53                 'Content-Type': 'text/plain',
  54         });
  55         response.write('Something went wrong. Sorry.');
  56         response.end();
  57 }
  58 var send_json = function(response) {
  59         response.writeHead(200, {
  60                 'Content-Type': 'text/json',
  61                 'X-Remoteglot-Last-Modified': json_last_modified,
  62                 'X-Remoteglot-Num-Viewers': count_viewers(),
  63                 'Access-Control-Allow-Origin': 'http://analysis.sesse.net',
  64                 'Access-Control-Expose-Headers': 'X-Remoteglot-Last-Modified, X-Remoteglot-Num-Viewers',
  65                 'Expires': 'Mon, 01 Jan 1970 00:00:00 UTC',
  66         });
  67         response.write(json_contents);
  68         response.end();
  69 }
  70 var timeout_client = function(client) {
  71         send_json(client.response);
  72         delete sleeping_clients[client.request_id];
  73 }
  74 var count_viewers = function() {
  75         var now = (new Date).getTime();
  76
  77         // Go through and remove old viewers, and count them at the same time.
  78         var new_last_seen_clients = {};
  79         var num_viewers = 0;
  80         for (var unique in last_seen_clients) {
  81                 if (now - last_seen_clients[unique] < 60000) {
  82                         ++num_viewers;
  83                         new_last_seen_clients[unique] = last_seen_clients[unique];
  84                 }
  85         }
  86         last_seen_clients = new_last_seen_clients;
  87         return num_viewers;
  88 }
  89
  90 // Set up a watcher to catch changes to the file, then do an initial read
  91 // to make sure we have a copy.
  92 fs.watch(json_filename, reread_file);
  93 reread_file();
  94
  95 http.createServer(function(request, response) {
  96         var u = url.parse(request.url, true);
  97         var ims = (u.query)['ims'];
  98         var unique = (u.query)['unique'];
  99
 100         console.log((new Date).getTime()*1e-3 + " " + request.url);
 101
 102         if (u.pathname !== '/analysis.pl') {
 103                 // This is not the request you are looking for.
 104                 send_404(response);
 105                 return;
 106         }
 107
 108         if (unique) {
 109                 last_seen_clients[unique] = (new Date).getTime();
 110         }
 111
 112         // If we already have something newer than what the user has,
 113         // just send it out and be done with it.
 114         if (!ims || json_last_modified > ims) {
 115                 send_json(response);
 116                 return;
 117         }
 118
 119         // OK, so we need to hang until we have something newer.
 120         // Put the user on the wait list; if we don't get anything
 121         // in 30 seconds, though, we'll send something anyway.
 122         var client = {};
 123         client.response = response;
 124         client.timer = setTimeout(function() { timeout_client(client); }, 30000);
 125         client.request_id = request_id;
 126         sleeping_clients[request_id++] = client;
 127 }).listen(5000);