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