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fix race conditions #2

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fix race conditions #2

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2 changes: 1 addition & 1 deletion index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@ var _ = require('underscore');
exports.setup = function(server, client, options) {
var self = this;

self.engine = options.engine || RedisEngine.create(options.servers);
self.engine = options.engine || RedisEngine.create(server, options.servers);
self.channelRe = options.channelRe || /^\/presence\//;

server.addExtension({
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184 changes: 119 additions & 65 deletions lib/redis_engine.js
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Original file line number Diff line number Diff line change
@@ -1,26 +1,75 @@
var ShardManager = require('shard-manager');
var redis = require('redis');
var Shavaluator = require('redis-evalsha');
var _ = require('underscore');

var RedisEngine = function(addresses) {
var RedisEngine = function(server, addresses) {
var shards = _.map(addresses, function(address, index) {
var components = address.split(':');
var hostname = components[0];
var port = components[1];

var client = redis.createClient(port, hostname);
var evalsha = new Shavaluator(client);

/*
ARGV[1] = clientId
ARGV[2] = data
ARGV[3] = presenceId
ARGV[4] = currentDate
KEYS[1] = data
KEYS[2] = pid
KEYS[3] = cids
KEYS[4] = pids
*/
evalsha.add('subscribe_presence', `
local exists = redis.call('EXISTS', KEYS[1])

redis.call('SET', KEYS[1], ARGV[2])
redis.call('SET', KEYS[2], ARGV[3])
redis.call('ZADD', KEYS[3], ARGV[4], ARGV[1])
redis.call('ZADD', KEYS[4], ARGV[4], ARGV[3])

return exists
`);

/*
ARGV[1] = clientId
ARGV[2] = presenceId
KEYS[1] = data
KEYS[2] = pid
KEYS[3] = cids
KEYS[4] = pids
*/
evalsha.add('unsubscribe_presence', `
redis.call('DEL', KEYS[2])
redis.call('ZREM', KEYS[3], ARGV[1])

if redis.call('EXISTS', KEYS[3]) == 1 then
return 1
end

redis.call('ZREM', KEYS[4], ARGV[2])
redis.call('DEL', KEYS[1])

return 0
`);

return {
shardName: 'node' + index,
shard: {
redis: redis.createClient(port, hostname)
evalsha: evalsha,
redis: client
}
};
});

this._server = server._server;
this._shardManager = new ShardManager(shards);
}

RedisEngine.create = function(server, options) {
return new RedisEngine(server, options);
RedisEngine.create = function(server, addresses, options) {
return new RedisEngine(server, addresses, options);
}

function key() {
Expand Down Expand Up @@ -64,29 +113,50 @@ RedisEngine.prototype = {
// ZADD cids:$channel:$presenceId $now $clientId
// ZADD pids:$channel $now $presenceId
var self = this;
var client = self._shardManager.getShard(channel).redis;

var isNew = true;
self._server.debug('Registering client ? for presence channel ? ?', clientId, channel, presenceId);

client.multi()
.exists(key('data', channel, presenceId), function(err, exists) {
if (exists == 1) {
isNew = false;
}
})
.set(key('data', channel, presenceId), data)
.set(key('pid', channel, clientId), presenceId)
.zadd(key('cids', channel, presenceId), Date.now(), clientId)
.zadd(key('pids', channel), Date.now(), presenceId)
.exec(function(err) {
if (err) {
console.log('redis error: ', err);
done(err);
return;
}
self._server._engine.clientExists(clientId, function (existsResult) {
if(!existsResult) {
self._server.debug('Will not register client ? for presence channel ? ?', clientId, channel, presenceId);

return;
}

done(null, isNew);
self._shardManager.getShard(channel).evalsha.exec('subscribe_presence', [
key('data', channel, presenceId),
key('pid', channel, clientId),
key('cids', channel, presenceId),
key('pids', channel),
], [
clientId,
data,
presenceId,
Date.now(),
], function (err, results) {
self._server._engine.clientExists(clientId, function (existsResult) {
if(!existsResult) {
self._server.debug('Client ? disappeared while registering for presence channel ? ?', clientId, channel, presenceId);

self.unsubscribe(channel, clientId);

done(null, false);

return;
} else if(results === 1) {
self._server.debug('Registered new client ? for presence channel ? ? ?', clientId, channel, presenceId);

done(null, false);
} else if(results === 0) {
self._server.debug('Registered initial client ? for presence channel ? ? ?', clientId, channel, presenceId);

done(null, true);
} else {
self._server.debug('Failed to register client ? for presence channel ? ? ? ?', clientId, channel, presenceId, err, results);
}
});
});
});
},

getSubscribers: function(channel, done) {
Expand Down Expand Up @@ -203,51 +273,35 @@ RedisEngine.prototype = {
var client = self._shardManager.getShard(channel).redis;

client.get(key('pid', channel, clientId), function(err, presenceId) {
if (err) {
console.log('error loading client presenceId', err);
done(err);
if(presenceId === null) {
self._server.debug('Will not deregister client ? for presence channel ? ?', clientId, channel, presenceId);

return;
}

var isLast = false;

client.multi()
.del(key('pid', channel, clientId), channel)
.zrem(key('cids', channel, presenceId), clientId)
.exists(key('cids', channel, presenceId), function(err, exists) {
if (err) {
console.log('error removing client subscription', err);
return;
}

if (exists == 0) {
isLast = true;
}
})
.exec(function(err) {
if (err) {
console.log('error removing client subscription', err);
done(err);
return;
}

if (!isLast) {
done(null, presenceId, false);
} else {
client.multi()
.zrem(key('pids', channel), presenceId)
.del(key('data', channel, presenceId))
.exec(function(err) {
if (err) {
console.log('error removing client subscription', err);
done(err);
return;
}

done(null, presenceId, true);
});
}
});
self._server.debug('Deregistering client ? for presence channel ? ?', clientId, channel, presenceId);

self._shardManager.getShard(channel).evalsha.exec('unsubscribe_presence', [
key('data', channel, presenceId),
key('pid', channel, clientId),
key('cids', channel, presenceId),
key('pids', channel),
], [
clientId,
presenceId,
], function (err, results) {
if(results === 1) {
self._server.debug('Deregistered client ? for presence channel ? ?', clientId, channel, presenceId);

if(done) done(null, presenceId, false);
} else if(results === 0) {
self._server.debug('Deregistered final client ? for presence channel ? ?', clientId, channel, presenceId);

if(done) done(null, presenceId, true);
} else {
self._server.debug('Failed to deregister client ? for presence channel ? ? ? ?', clientId, channel, presenceId, err, results);
}
});
});
}
};
Expand Down