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 // If we are behind Varnish, we can't count the number of clients
  36 // ourselves, so some external log-tailing daemon needs to tell us.
  37 var viewer_count_override = undefined;
  38
  39 var reread_file = function(event, filename) {
  40         if (filename != path.basename(json_filename)) {
  41                 return;
  42         }
  43         console.log("Rereading " + json_filename);
  44         fs.open(json_filename, 'r+', function(err, fd) {
  45                 if (err) throw err;
  46                 fs.fstat(fd, function(err, st) {
  47                         if (err) throw err;
  48                         var buffer = new Buffer(1048576);
  49                         fs.read(fd, buffer, 0, 1048576, 0, function(err, bytesRead, buffer) {
  50                                 if (err) throw err;
  51                                 fs.close(fd, function() {
  52                                         var new_json_contents = buffer.toString('utf8', 0, bytesRead);
  53                                         zlib.gzip(new_json_contents, function(err, buffer) {
  54                                                 if (err) throw err;
  55                                                 json_contents = new_json_contents;
  56                                                 json_contents_gz = buffer;
  57                                                 json_last_modified = st.mtime.getTime();
  58                                                 possibly_wakeup_clients();
  59                                         });
  60                                 });
  61                         });
  62                 });
  63         });
  64
  65         if (touch_timer !== undefined) {
  66                 clearTimeout(touch_timer);
  67         }
  68         touch_timer = setTimeout(function() {
  69                 console.log("Touching analysis.json due to no other activity");
  70                 var now = Date.now() / 1000;
  71                 fs.utimes(json_filename, now, now);
  72         }, 30000);
  73 }
  74 var possibly_wakeup_clients = function() {
  75         var num_viewers = count_viewers();
  76         for (var i in sleeping_clients) {
  77                 mark_recently_seen(sleeping_clients[i].unique);
  78                 send_json(sleeping_clients[i].response,
  79                           sleeping_clients[i].accept_gzip,
  80                           num_viewers);
  81         }
  82         sleeping_clients = {};
  83 }
  84 var send_404 = function(response) {
  85         response.writeHead(404, {
  86                 'Content-Type': 'text/plain',
  87         });
  88         response.write('Something went wrong. Sorry.');
  89         response.end();
  90 }
  91 var handle_viewer_override = function(request, u, response) {
  92         // Only accept requests from localhost.
  93         var peer = request.socket.localAddress;
  94         if ((peer != '127.0.0.1' && peer != '::1') || request.headers['x-forwarded-for']) {
  95                 console.log("Refusing viewer override from " + peer);
  96                 send_404(response);
  97         } else {
  98                 viewer_count_override = (u.query)['num'];
  99                 response.writeHead(200, {
 100                         'Content-Type': 'text/plain',
 101                 });
 102                 response.write('OK.');
 103                 response.end();
 104         }
 105 }
 106 var send_json = function(response, accept_gzip, num_viewers) {
 107         var headers = {
 108                 'Content-Type': 'text/json',
 109                 'X-Remoteglot-Last-Modified': json_last_modified,
 110                 'X-Remoteglot-Num-Viewers': num_viewers,
 111                 'Access-Control-Expose-Headers': 'X-Remoteglot-Last-Modified, X-Remoteglot-Num-Viewers',
 112                 'Expires': 'Mon, 01 Jan 1970 00:00:00 UTC',
 113                 'Vary': 'Accept-Encoding',
 114         };
 115
 116         if (accept_gzip) {
 117                 headers['Content-Encoding'] = 'gzip';
 118                 response.writeHead(200, headers);
 119                 response.write(json_contents_gz);
 120         } else {
 121                 response.writeHead(200, headers);
 122                 response.write(json_contents);
 123         }
 124         response.end();
 125 }
 126 var mark_recently_seen = function(unique) {
 127         if (unique) {
 128                 last_seen_clients[unique] = (new Date).getTime();
 129         }
 130 }
 131 var count_viewers = function() {
 132         if (viewer_count_override !== undefined) {
 133                 return viewer_count_override;
 134         }
 135
 136         var now = (new Date).getTime();
 137
 138         // Go through and remove old viewers, and count them at the same time.
 139         var new_last_seen_clients = {};
 140         var num_viewers = 0;
 141         for (var unique in last_seen_clients) {
 142                 if (now - last_seen_clients[unique] < 5000) {
 143                         ++num_viewers;
 144                         new_last_seen_clients[unique] = last_seen_clients[unique];
 145                 }
 146         }
 147
 148         // Also add sleeping clients that we would otherwise assume timed out.
 149         for (var request_id in sleeping_clients) {
 150                 var unique = sleeping_clients[request_id].unique;
 151                 if (unique && !(unique in new_last_seen_clients)) {
 152                         ++num_viewers;
 153                 }
 154         }
 155
 156         last_seen_clients = new_last_seen_clients;
 157         return num_viewers;
 158 }
 159
 160 // Set up a watcher to catch changes to the file, then do an initial read
 161 // to make sure we have a copy.
 162 fs.watch(path.dirname(json_filename), reread_file);
 163 reread_file(null, path.basename(json_filename));
 164
 165 var server = http.createServer();
 166 server.on('request', function(request, response) {
 167         var u = url.parse(request.url, true);
 168         var ims = (u.query)['ims'];
 169         var unique = (u.query)['unique'];
 170
 171         console.log((new Date).getTime()*1e-3 + " " + request.url);
 172         if (u.pathname === '/override-num-viewers') {
 173                 handle_viewer_override(request, u, response);
 174                 return;
 175         }
 176         if (u.pathname !== '/analysis.pl') {
 177                 // This is not the request you are looking for.
 178                 send_404(response);
 179                 return;
 180         }
 181
 182         mark_recently_seen(unique);
 183
 184         var accept_encoding = request.headers['accept-encoding'];
 185         var accept_gzip;
 186         if (accept_encoding !== undefined && accept_encoding.match(/\bgzip\b/)) {
 187                 accept_gzip = true;
 188         } else {
 189                 accept_gzip = false;
 190         }
 191
 192         // If we already have something newer than what the user has,
 193         // just send it out and be done with it.
 194         if (json_last_modified !== undefined && (!ims || json_last_modified > ims)) {
 195                 send_json(response, accept_gzip, count_viewers());
 196                 return;
 197         }
 198
 199         // OK, so we need to hang until we have something newer.
 200         // Put the user on the wait list.
 201         var client = {};
 202         client.response = response;
 203         client.request_id = request_id;
 204         client.accept_gzip = accept_gzip;
 205         client.unique = unique;
 206         sleeping_clients[request_id++] = client;
 207
 208         request.socket.client = client;
 209 });
 210 server.on('connection', function(socket) {
 211         socket.on('close', function() {
 212                 var client = socket.client;
 213                 if (client) {
 214                         mark_recently_seen(client.unique);
 215                         delete sleeping_clients[client.request_id];
 216                 }
 217         });
 218 });
 219 server.listen(5000);