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 = undefined;
  17
  18 // The list of clients that are waiting for new data to show up.
  19 // Uniquely keyed by request_id so that we can take them out of
  20 // the queue if they close the socket.
  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 // The timer used to touch the file every 30 seconds if nobody
  29 // else does it for us. This makes sure we don't have clients
  30 // hanging indefinitely (which might have them return errors).
  31 var touch_timer = undefined;
  32
  33 // If we are behind Varnish, we can't count the number of clients
  34 // ourselves, so some external log-tailing daemon needs to tell us.
  35 var viewer_count_override = undefined;
  36
  37 var replace_json = function(new_json_contents, mtime) {
  38         var new_json = {
  39                 parsed: JSON.parse(new_json_contents),
  40                 plain: new_json_contents,
  41                 last_modified: mtime
  42         };
  43
  44         // gzip the new version, and put it into place.
  45         zlib.gzip(new_json_contents, function(err, buffer) {
  46                 if (err) throw err;
  47
  48                 new_json.gzip = buffer;
  49                 json = new_json;
  50
  51                 // Finally, wake up any sleeping clients.
  52                 possibly_wakeup_clients();
  53         });
  54 }
  55
  56 var reread_file = function(event, filename) {
  57         if (filename != path.basename(json_filename)) {
  58                 return;
  59         }
  60         console.log("Rereading " + json_filename);
  61         fs.open(json_filename, 'r+', function(err, fd) {
  62                 if (err) throw err;
  63                 fs.fstat(fd, function(err, st) {
  64                         if (err) throw err;
  65                         var buffer = new Buffer(1048576);
  66                         fs.read(fd, buffer, 0, 1048576, 0, function(err, bytesRead, buffer) {
  67                                 if (err) throw err;
  68                                 fs.close(fd, function() {
  69                                         var new_json_contents = buffer.toString('utf8', 0, bytesRead);
  70                                         replace_json(new_json_contents, st.mtime.getTime());
  71                                 });
  72                         });
  73                 });
  74         });
  75
  76         if (touch_timer !== undefined) {
  77                 clearTimeout(touch_timer);
  78         }
  79         touch_timer = setTimeout(function() {
  80                 console.log("Touching analysis.json due to no other activity");
  81                 var now = Date.now() / 1000;
  82                 fs.utimes(json_filename, now, now);
  83         }, 30000);
  84 }
  85 var possibly_wakeup_clients = function() {
  86         var num_viewers = count_viewers();
  87         for (var i in sleeping_clients) {
  88                 mark_recently_seen(sleeping_clients[i].unique);
  89                 send_json(sleeping_clients[i].response,
  90                           sleeping_clients[i].accept_gzip,
  91                           num_viewers);
  92         }
  93         sleeping_clients = {};
  94 }
  95 var send_404 = function(response) {
  96         response.writeHead(404, {
  97                 'Content-Type': 'text/plain',
  98         });
  99         response.write('Something went wrong. Sorry.');
 100         response.end();
 101 }
 102 var handle_viewer_override = function(request, u, response) {
 103         // Only accept requests from localhost.
 104         var peer = request.socket.localAddress;
 105         if ((peer != '127.0.0.1' && peer != '::1') || request.headers['x-forwarded-for']) {
 106                 console.log("Refusing viewer override from " + peer);
 107                 send_404(response);
 108         } else {
 109                 viewer_count_override = (u.query)['num'];
 110                 response.writeHead(200, {
 111                         'Content-Type': 'text/plain',
 112                 });
 113                 response.write('OK.');
 114                 response.end();
 115         }
 116 }
 117 var send_json = function(response, accept_gzip, num_viewers) {
 118         var headers = {
 119                 'Content-Type': 'text/json',
 120                 'X-Remoteglot-Last-Modified': json.last_modified,
 121                 'X-Remoteglot-Num-Viewers': num_viewers,
 122                 'Access-Control-Expose-Headers': 'X-Remoteglot-Last-Modified, X-Remoteglot-Num-Viewers',
 123                 'Expires': 'Mon, 01 Jan 1970 00:00:00 UTC',
 124                 'Vary': 'Accept-Encoding',
 125         };
 126
 127         if (accept_gzip) {
 128                 headers['Content-Encoding'] = 'gzip';
 129                 response.writeHead(200, headers);
 130                 response.write(json.gzip);
 131         } else {
 132                 response.writeHead(200, headers);
 133                 response.write(json.text);
 134         }
 135         response.end();
 136 }
 137 var mark_recently_seen = function(unique) {
 138         if (unique) {
 139                 last_seen_clients[unique] = (new Date).getTime();
 140         }
 141 }
 142 var count_viewers = function() {
 143         if (viewer_count_override !== undefined) {
 144                 return viewer_count_override;
 145         }
 146
 147         var now = (new Date).getTime();
 148
 149         // Go through and remove old viewers, and count them at the same time.
 150         var new_last_seen_clients = {};
 151         var num_viewers = 0;
 152         for (var unique in last_seen_clients) {
 153                 if (now - last_seen_clients[unique] < 5000) {
 154                         ++num_viewers;
 155                         new_last_seen_clients[unique] = last_seen_clients[unique];
 156                 }
 157         }
 158
 159         // Also add sleeping clients that we would otherwise assume timed out.
 160         for (var request_id in sleeping_clients) {
 161                 var unique = sleeping_clients[request_id].unique;
 162                 if (unique && !(unique in new_last_seen_clients)) {
 163                         ++num_viewers;
 164                 }
 165         }
 166
 167         last_seen_clients = new_last_seen_clients;
 168         return num_viewers;
 169 }
 170
 171 // Set up a watcher to catch changes to the file, then do an initial read
 172 // to make sure we have a copy.
 173 fs.watch(path.dirname(json_filename), reread_file);
 174 reread_file(null, path.basename(json_filename));
 175
 176 var server = http.createServer();
 177 server.on('request', function(request, response) {
 178         var u = url.parse(request.url, true);
 179         var ims = (u.query)['ims'];
 180         var unique = (u.query)['unique'];
 181
 182         console.log((new Date).getTime()*1e-3 + " " + request.url);
 183         if (u.pathname === '/override-num-viewers') {
 184                 handle_viewer_override(request, u, response);
 185                 return;
 186         }
 187         if (u.pathname !== '/analysis.pl') {
 188                 // This is not the request you are looking for.
 189                 send_404(response);
 190                 return;
 191         }
 192
 193         mark_recently_seen(unique);
 194
 195         var accept_encoding = request.headers['accept-encoding'];
 196         var accept_gzip;
 197         if (accept_encoding !== undefined && accept_encoding.match(/\bgzip\b/)) {
 198                 accept_gzip = true;
 199         } else {
 200                 accept_gzip = false;
 201         }
 202
 203         // If we already have something newer than what the user has,
 204         // just send it out and be done with it.
 205         if (json !== undefined && (!ims || json.last_modified > ims)) {
 206                 send_json(response, accept_gzip, count_viewers());
 207                 return;
 208         }
 209
 210         // OK, so we need to hang until we have something newer.
 211         // Put the user on the wait list.
 212         var client = {};
 213         client.response = response;
 214         client.request_id = request_id;
 215         client.accept_gzip = accept_gzip;
 216         client.unique = unique;
 217         sleeping_clients[request_id++] = client;
 218
 219         request.socket.client = client;
 220 });
 221 server.on('connection', function(socket) {
 222         socket.on('close', function() {
 223                 var client = socket.client;
 224                 if (client) {
 225                         mark_recently_seen(client.unique);
 226                         delete sleeping_clients[client.request_id];
 227                 }
 228         });
 229 });
 230 server.listen(5000);