Version bump.
[remoteglot] / server / 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 var readline = require('readline');
12 var child_process = require('child_process');
13 var delta = require('../www/js/json_delta.js');
14 var hash_lookup = require('./hash-lookup.js');
15
16 // Constants.
17 var HISTORY_TO_KEEP = 5;
18 var MINIMUM_VERSION = null;
19 var COUNT_FROM_VARNISH_LOG = true;
20
21 // Filename to serve.
22 var json_filename = '/srv/analysis.sesse.net/www/analysis.json';
23 if (process.argv.length >= 3) {
24         json_filename = process.argv[2];
25 }
26
27 // Expected destination filenames.
28 var serve_url = '/analysis.pl';
29 var hash_serve_url = '/hash';
30 if (process.argv.length >= 4) {
31         serve_url = process.argv[3];
32 }
33 if (process.argv.length >= 5) {
34         hash_serve_url = process.argv[4];
35 }
36
37 // TCP port to listen on.
38 var port = 5000;
39 if (process.argv.length >= 6) {
40         port = parseInt(process.argv[5]);
41 }
42
43 // gRPC backends.
44 var grpc_backends = ["localhost:50051", "localhost:50052"];
45 if (process.argv.length >= 7) {
46         grpc_backends = process.argv[6].split(",");
47 }
48 hash_lookup.init(grpc_backends);
49
50 // If set to 1, we are already processing a JSON update and should not
51 // start a new one. If set to 2, we are _also_ having one in the queue.
52 var json_lock = 0;
53
54 // The current contents of the file to hand out, and its last modified time.
55 var json = undefined;
56
57 // The last five timestamps, and diffs from them to the latest version.
58 var historic_json = [];
59 var diff_json = {};
60
61 // The list of clients that are waiting for new data to show up.
62 // Uniquely keyed by request_id so that we can take them out of
63 // the queue if they close the socket.
64 var sleeping_clients = {};
65 var request_id = 0;
66
67 // List of when clients were last seen, keyed by their unique ID.
68 // Used to show a viewer count to the user.
69 var last_seen_clients = {};
70
71 // The timer used to touch the file every 30 seconds if nobody
72 // else does it for us. This makes sure we don't have clients
73 // hanging indefinitely (which might have them return errors).
74 var touch_timer = undefined;
75
76 // If we are behind Varnish, we can't count the number of clients
77 // ourselves, so we need to get it from parsing varnishncsa.
78 var viewer_count_override = undefined;
79
80 var replace_json = function(new_json_contents, mtime) {
81         // Generate the list of diffs from the last five versions.
82         if (json !== undefined) {
83                 // If two versions have the same mtime, clients could have either.
84                 // Note the fact, so that we never insert it.
85                 if (json.last_modified == mtime) {
86                         json.invalid_base = true;
87                 }
88                 if (!json.invalid_base) {
89                         historic_json.push(json);
90                         if (historic_json.length > HISTORY_TO_KEEP) {
91                                 historic_json.shift();
92                         }
93                 }
94         }
95
96         var new_json = {
97                 parsed: JSON.parse(new_json_contents),
98                 plain: new_json_contents,
99                 last_modified: mtime
100         };
101         create_json_historic_diff(new_json, historic_json.slice(0), {}, function(new_diff_json) {
102                 // gzip the new version (non-delta), and put it into place.
103                 zlib.gzip(new_json_contents, function(err, buffer) {
104                         if (err) throw err;
105
106                         new_json.gzip = buffer;
107                         json = new_json;
108                         diff_json = new_diff_json;
109                         json_lock = 0;
110
111                         // Finally, wake up any sleeping clients.
112                         possibly_wakeup_clients();
113                 });
114         });
115 }
116
117 var create_json_historic_diff = function(new_json, history_left, new_diff_json, cb) {
118         if (history_left.length == 0) {
119                 cb(new_diff_json);
120                 return;
121         }
122
123         var histobj = history_left.shift();
124         var diff = delta.JSON_delta.diff(histobj.parsed, new_json.parsed);
125         var diff_text = JSON.stringify(diff);
126         zlib.gzip(diff_text, function(err, buffer) {
127                 if (err) throw err;
128                 new_diff_json[histobj.last_modified] = {
129                         parsed: diff,
130                         plain: diff_text,
131                         gzip: buffer,
132                         last_modified: new_json.last_modified,
133                 };
134                 create_json_historic_diff(new_json, history_left, new_diff_json, cb);
135         });
136 }
137
138 var reread_file = function(event, filename) {
139         if (filename != path.basename(json_filename)) {
140                 return;
141         }
142         if (json_lock >= 2) {
143                 return;
144         }
145         if (json_lock == 1) {
146                 // Already processing; wait a bit.
147                 json_lock = 2;
148                 setTimeout(function() { json_lock = 1; reread_file(event, filename); }, 100);
149                 return;
150         }
151         json_lock = 1;
152
153         console.log("Rereading " + json_filename);
154         fs.open(json_filename, 'r', function(err, fd) {
155                 if (err) throw err;
156                 fs.fstat(fd, function(err, st) {
157                         if (err) throw err;
158                         var buffer = new Buffer(1048576);
159                         fs.read(fd, buffer, 0, 1048576, 0, function(err, bytesRead, buffer) {
160                                 if (err) throw err;
161                                 fs.close(fd, function() {
162                                         var new_json_contents = buffer.toString('utf8', 0, bytesRead);
163                                         replace_json(new_json_contents, st.mtime.getTime());
164                                 });
165                         });
166                 });
167         });
168
169         if (touch_timer !== undefined) {
170                 clearTimeout(touch_timer);
171         }
172         touch_timer = setTimeout(function() {
173                 console.log("Touching analysis.json due to no other activity");
174                 var now = Date.now() / 1000;
175                 fs.utimes(json_filename, now, now);
176         }, 30000);
177 }
178 var possibly_wakeup_clients = function() {
179         var num_viewers = count_viewers();
180         for (var i in sleeping_clients) {
181                 mark_recently_seen(sleeping_clients[i].unique);
182                 send_json(sleeping_clients[i].response,
183                           sleeping_clients[i].ims,
184                           sleeping_clients[i].accept_gzip,
185                           num_viewers);
186         }
187         sleeping_clients = {};
188 }
189 var send_404 = function(response) {
190         response.writeHead(404, {
191                 'Content-Type': 'text/plain',
192         });
193         response.write('Something went wrong. Sorry.');
194         response.end();
195 }
196 var send_json = function(response, ims, accept_gzip, num_viewers) {
197         var this_json = diff_json[ims] || json;
198
199         var headers = {
200                 'Content-Type': 'text/json',
201                 'X-RGLM': this_json.last_modified,
202                 'X-RGNV': num_viewers,
203                 'Access-Control-Expose-Headers': 'X-RGLM, X-RGNV, X-RGMV',
204                 'Vary': 'Accept-Encoding',
205         };
206
207         if (MINIMUM_VERSION) {
208                 headers['X-RGMV'] = MINIMUM_VERSION;
209         }
210
211         if (accept_gzip) {
212                 headers['Content-Length'] = this_json.gzip.length;
213                 headers['Content-Encoding'] = 'gzip';
214                 response.writeHead(200, headers);
215                 response.write(this_json.gzip);
216         } else {
217                 headers['Content-Length'] = this_json.plain.length;
218                 response.writeHead(200, headers);
219                 response.write(this_json.plain);
220         }
221         response.end();
222 }
223 var mark_recently_seen = function(unique) {
224         if (unique) {
225                 last_seen_clients[unique] = (new Date).getTime();
226         }
227 }
228 var count_viewers = function() {
229         if (viewer_count_override !== undefined) {
230                 return viewer_count_override;
231         }
232
233         var now = (new Date).getTime();
234
235         // Go through and remove old viewers, and count them at the same time.
236         var new_last_seen_clients = {};
237         var num_viewers = 0;
238         for (var unique in last_seen_clients) {
239                 if (now - last_seen_clients[unique] < 5000) {
240                         ++num_viewers;
241                         new_last_seen_clients[unique] = last_seen_clients[unique];
242                 }
243         }
244
245         // Also add sleeping clients that we would otherwise assume timed out.
246         for (var request_id in sleeping_clients) {
247                 var unique = sleeping_clients[request_id].unique;
248                 if (unique && !(unique in new_last_seen_clients)) {
249                         ++num_viewers;
250                 }
251         }
252
253         last_seen_clients = new_last_seen_clients;
254         return num_viewers;
255 }
256 var log = function(str) {
257         console.log("[" + ((new Date).getTime()*1e-3).toFixed(3) + "] " + str);
258 }
259
260 // Set up a watcher to catch changes to the file, then do an initial read
261 // to make sure we have a copy.
262 fs.watch(path.dirname(json_filename), reread_file);
263 reread_file(null, path.basename(json_filename));
264
265 if (COUNT_FROM_VARNISH_LOG) {
266         // Note: We abuse serve_url as a regex.
267         var varnishncsa = child_process.spawn(
268                 'varnishncsa', ['-F', '%{%s}t %U %q tffb=%{Varnish:time_firstbyte}x',
269                 '-q', 'ReqURL ~ "^' + serve_url + '"']);
270         var rl = readline.createInterface({
271                 input: varnishncsa.stdout,
272                 output: varnishncsa.stdin,
273                 terminal: false
274         });
275
276         var uniques = [];
277         rl.on('line', function(line) {
278                 var v = line.match(/(\d+) .*\?ims=\d+&unique=(.*) tffb=(.*)/);
279                 if (v) {
280                         uniques[v[2]] = {
281                                 last_seen: (parseInt(v[1]) + parseFloat(v[3])) * 1e3,
282                                 grace: null,
283                         };
284                         log(v[1] + " " + v[2] + " " + v[3]);
285                 } else {
286                         log("VARNISHNCSA UNPARSEABLE LINE: " + line);
287                 }
288         });
289         setInterval(function() {
290                 var mtime = json.last_modified - 1000;  // Compensate for subsecond issues.
291                 var now = (new Date).getTime();
292                 var num_viewers = 0;
293
294                 for (var unique in uniques) {
295                         ++num_viewers;
296                         var last_seen = uniques[unique].last_seen;
297                         if (now - last_seen <= 5000) {
298                                 // We've seen this user in the last five seconds;
299                                 // it's okay.
300                                 continue;
301                         }
302                         if (last_seen >= mtime) {
303                                 // This user has the latest version;
304                                 // they are probably just hanging.
305                                 continue;
306                         }
307                         if (uniques[unique].grace === null) {
308                                 // They have five seconds after a new JSON has been
309                                 // provided to get get it, or they're out.
310                                 // We don't simply use mtime, since we don't want to
311                                 // reset the grace timer just because a new JSON is
312                                 // published.
313                                 uniques[unique].grace = mtime;
314                         }
315                         if (now - uniques[unique].grace > 5000) {
316                                 log("Timing out " + unique + " (last_seen=" + last_seen + ", now=" + now +
317                                         ", mtime=" + mtime, ", grace=" + uniques[unique].grace + ")");
318                                 delete uniques[unique];
319                                 --num_viewers;
320                         }
321                 }
322
323                 log(num_viewers + " entries in hash, mtime=" + mtime);
324                 viewer_count_override = num_viewers;
325         }, 1000);
326 }
327
328 var server = http.createServer();
329 server.on('request', function(request, response) {
330         var u = url.parse(request.url, true);
331         var ims = (u.query)['ims'];
332         var unique = (u.query)['unique'];
333
334         log(request.url);
335         if (u.pathname === hash_serve_url) {
336                 var fen = (u.query)['fen'];
337                 hash_lookup.handle_request(fen, response);
338                 return;
339         }
340         if (u.pathname !== serve_url) {
341                 // This is not the request you are looking for.
342                 send_404(response);
343                 return;
344         }
345
346         mark_recently_seen(unique);
347
348         var accept_encoding = request.headers['accept-encoding'];
349         var accept_gzip;
350         if (accept_encoding !== undefined && accept_encoding.match(/\bgzip\b/)) {
351                 accept_gzip = true;
352         } else {
353                 accept_gzip = false;
354         }
355
356         // If we already have something newer than what the user has,
357         // just send it out and be done with it.
358         if (json !== undefined && (!ims || json.last_modified > ims)) {
359                 send_json(response, ims, accept_gzip, count_viewers());
360                 return;
361         }
362
363         // OK, so we need to hang until we have something newer.
364         // Put the user on the wait list.
365         var client = {};
366         client.response = response;
367         client.request_id = request_id;
368         client.accept_gzip = accept_gzip;
369         client.unique = unique;
370         client.ims = ims;
371         sleeping_clients[request_id++] = client;
372
373         request.socket.client = client;
374 });
375 server.on('connection', function(socket) {
376         socket.on('close', function() {
377                 var client = socket.client;
378                 if (client) {
379                         mark_recently_seen(client.unique);
380                         delete sleeping_clients[client.request_id];
381                 }
382         });
383 });
384
385 server.listen(port);