1 // node.js version of analysis.pl; hopefully scales a bit better
2 // for this specific kind of task.
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');
13 var json_filename = '/srv/analysis.sesse.net/www/analysis.json';
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;
20 // The list of clients that are waiting for new data to show up,
21 // and their associated timers. Uniquely keyed by request_id
22 // so that we can take them out of the queue if they time out.
23 var sleeping_clients = {};
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 = {};
30 var reread_file = function(event, filename) {
31 if (filename != path.basename(json_filename)) {
34 console.log("Rereading " + json_filename);
35 fs.open(json_filename, 'r+', function(err, fd) {
37 fs.fstat(fd, function(err, st) {
39 var buffer = new Buffer(1048576);
40 fs.read(fd, buffer, 0, 1048576, 0, function(err, bytesRead, buffer) {
42 fs.close(fd, function() {
43 var new_json_contents = buffer.toString('utf8', 0, bytesRead);
44 zlib.gzip(new_json_contents, function(err, buffer) {
46 json_contents = new_json_contents;
47 json_contents_gz = buffer;
48 json_last_modified = st.mtime.getTime();
49 possibly_wakeup_clients();
56 var possibly_wakeup_clients = function() {
57 for (var i in sleeping_clients) {
58 clearTimeout(sleeping_clients[i].timer);
59 mark_recently_seen(sleeping_clients[request_id].unique);
60 send_json(sleeping_clients[i].response, sleeping_clients[i].accept_gzip);
62 sleeping_clients = {};
64 var send_404 = function(response) {
65 response.writeHead(404, {
66 'Content-Type': 'text/plain',
68 response.write('Something went wrong. Sorry.');
71 var send_json = function(response, accept_gzip) {
73 'Content-Type': 'text/json',
74 'X-Remoteglot-Last-Modified': json_last_modified,
75 'X-Remoteglot-Num-Viewers': count_viewers(),
76 'Access-Control-Allow-Origin': 'http://analysis.sesse.net',
77 'Access-Control-Expose-Headers': 'X-Remoteglot-Last-Modified, X-Remoteglot-Num-Viewers',
78 'Expires': 'Mon, 01 Jan 1970 00:00:00 UTC',
82 headers['Content-Encoding'] = 'gzip';
83 response.writeHead(200, headers);
84 response.write(json_contents_gz);
86 response.writeHead(200, headers);
87 response.write(json_contents);
91 var timeout_client = function(client) {
92 mark_recently_seen(client.unique);
93 send_json(client.response, client.accept_gzip);
94 delete sleeping_clients[client.request_id];
96 var mark_recently_seen = function(unique) {
98 last_seen_clients[unique] = (new Date).getTime();
101 var count_viewers = function() {
102 var now = (new Date).getTime();
104 // Go through and remove old viewers, and count them at the same time.
105 var new_last_seen_clients = {};
107 for (var unique in last_seen_clients) {
108 if (now - last_seen_clients[unique] < 5000) {
110 new_last_seen_clients[unique] = last_seen_clients[unique];
114 // Also add sleeping clients that we would otherwise assume timed out.
115 for (var request_id in sleeping_clients) {
116 var unique = sleeping_clients[request_id].unique;
117 if (unique && !(unique in new_last_seen_clients)) {
122 last_seen_clients = new_last_seen_clients;
126 // Set up a watcher to catch changes to the file, then do an initial read
127 // to make sure we have a copy.
128 fs.watch(path.dirname(json_filename), reread_file);
129 reread_file(null, path.basename(json_filename));
131 http.createServer(function(request, response) {
132 var u = url.parse(request.url, true);
133 var ims = (u.query)['ims'];
134 var unique = (u.query)['unique'];
136 console.log((new Date).getTime()*1e-3 + " " + request.url);
138 if (u.pathname !== '/analysis.pl') {
139 // This is not the request you are looking for.
144 mark_recently_seen(unique);
146 var accept_encoding = request.headers['accept-encoding'];
148 if (accept_encoding !== undefined && accept_encoding.match(/\bgzip\b/)) {
154 // If we already have something newer than what the user has,
155 // just send it out and be done with it.
156 if (json_last_modified !== undefined && (!ims || json_last_modified > ims)) {
157 send_json(response, accept_gzip);
161 // OK, so we need to hang until we have something newer.
162 // Put the user on the wait list; if we don't get anything
163 // in 30 seconds, though, we'll send something anyway.
165 client.response = response;
166 client.timer = setTimeout(function() { timeout_client(client); }, 30000);
167 client.request_id = request_id;
168 client.accept_gzip = accept_gzip;
169 client.unique = unique;
170 sleeping_clients[request_id++] = client;