EntryPool

Simple array pooling with entry (i.e. time) adding/counting for simple rate limiting. See the example at the bottom for help with using this for rate limiting.

EntryPool Methods

pool = new EntryPool(initialSize, arrayLength[,stepSize])

Returns a new pool of arrays of length arrayLength with an initial size of initialSize. stepSize is used when adding to the poll and defaults to initialSize or "double pool".

pool.get()

Gets a new EntryArray of length arrayLength from the pool.

pool.put(array)

Puts back an EntryArray once its done being used.

pool.add([num])

Adds num arrays of length arrayLength to the pool. If no num is passed, it will use the step size.

pool.trim([minSize])

Reduces pool size to at least minSize (or 0) by removing unused arrays from the pool.

EntryArray Methods

arr.add(timestamp[, value])

Adds an entry to the array. You should add an entry for each thing you want to limit. Returns the index at which entry was added or -1 if array is full.

arr.remove([timestamp][, value])

Removes an entry from array. Returns true if array is now empty. timestamp and value are both optional and to omit timestamp but send value pass undefined as timestamp.

arr.cleanup(maxEntry)

Removes any entries with a timestamp older than maxEntry from array. Returns number of entries left.

arr.numEntries()

Removes the number of entries in array.

Example

var connectionsPerIP = {},
    //only allow up to 5 connections every minute
    maxAllowedConnections = 5,
    maxAllowedTimeframe = 60 * 1000,
    pool = new EntryPool(100, maxAllowedConnections); 
 
// server is a http.Server
server.on('connection', function(socket) {
    var now = Date.now(),
        ip = socket.remoteAddress;
    if (!connectionsPerIP[ip]) {
        connectionsPerIP[ip] = pool.get();
    } else {
        // remove any entries older than the allowed timeframe
        connectionsPerIP[ip].cleanup(now - maxAllowedTimeframe);
    }
    // store that they just connected
    if (connectionsPerIP[ip].add(now) < 0) {
        // the user is over the rate-limit so end the connection immediately 
        socket.end();
        return;
    }
    socket.on('close', function() {
        // if the array is now empty then we need to remove it
        if (connectionsPerIP[ip].cleanup(now - maxAllowedTimeframe) === 0) {
            pool.put(connectionsPerIP[ip]);
            delete connectionsPerIP[ip];
        }
    });
};
    
// if a connection was open for less than maxAllowedTimeframe then we didn't remove the entry from
// the array when they closed. this interval will cleanup any that are expired
setInterval(function() {
    var cleanupIfBefore = Date.now() - maxAllowedTimeframe;
    for (var ip in connectionsPerIP) {
        if (connectionsPerIP[ip].cleanup(cleanupIfBefore) === 0) {
            pool.put(connectionsPerIP[ip]);
            delete connectionsPerIP[ip];
        }
    }
}, 10 * maxAllowedTimeframe);
 

By James Hartig