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Merge branch 'load-balance' of github.com:atrniv/ndns into load-balance
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@ssbanerje
ssbanerje committed Nov 12, 2011
2 parents 13851e7 + cf0e633 commit e24eb05
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235 changes: 164 additions & 71 deletions README.md
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Expand Up @@ -5,30 +5,30 @@ ndns -- dns client/server library for nodejs

An example DNS server written with node which responds 'Hello World':

var ndns = require('ndns');

ndns.createServer('udp4', function (req, res) {
res.setHeader(req.header);
res.header.qr = 1;
res.header.aa = 1;
res.header.rd = 0;
res.header.ra = 0;
res.header.ancount = 0;
for (var i = 0; i < req.q.length; i++) {
res.q.add(req.q[i]);
res.addRR(req.q[i].name, 3600, ndns.ns_t.txt, "hello, world");
res.header.ancount++;
}
res.send();
}).bind(5300);

console.log("Server running at 0.0.0.0:5300")
var ndns = require('ndns');

ndns.createServer('udp4', function (req, res) {
res.setHeader(req.header);
res.header.qr = 1;
res.header.aa = 1;
res.header.rd = 0;
res.header.ra = 0;
res.header.ancount = 0;
for (var i = 0; i < req.q.length; i++) {
res.q.add(req.q[i]);
res.addRR(req.q[i].name, 3600, ndns.ns_t.txt, "hello, world");
res.header.ancount++;
}
res.send();
}).bind(5300);

console.log("Server running at 0.0.0.0:5300")

To run the server, put the code into a file called example.js and execute it
with the node program:

\> node example.js
Server running at 0.0.0.0:5300
\> node example.js
Server running at 0.0.0.0:5300

All of the examples in the documentation can be run similarly.

Expand All @@ -38,49 +38,49 @@ To use the ndns server and client one must require('ndns').

DNS request messages are represented by an object like this:

{ header:
{ id: 39545
, qr: 0
, opcode: 0
, aa: 0
, tc: 0
, rd: 1
, ra: 0
, z: 0
, ad: 0
, cd: 0
, rcode: 0
, qdcount: 1
, ancount: 0
, nscount: 0
, arcount: 0
}
, q:
{ '0':
{ name: 'example.com'
, type: 1
, class: 1
}
, length: 1
}
, rr:
{ '0':
{ name: 'example.com'
, ttl: 3600
, class: 1
, type: 1
, rdata: '127.0.0.1'
}
'1':
{ name: 'example.com'
, ttl: 3600
, class: 1
, type: 1
, rdata: '127.0.0.2'
}
, length: 2
}
}
{ header:
{ id: 39545
, qr: 0
, opcode: 0
, aa: 0
, tc: 0
, rd: 1
, ra: 0
, z: 0
, ad: 0
, cd: 0
, rcode: 0
, qdcount: 1
, ancount: 0
, nscount: 0
, arcount: 0
}
, q:
{ '0':
{ name: 'example.com'
, type: 1
, class: 1
}
, length: 1
}
, rr:
{ '0':
{ name: 'example.com'
, ttl: 3600
, class: 1
, type: 1
, rdata: '127.0.0.1'
}
'1':
{ name: 'example.com'
, ttl: 3600
, class: 1
, type: 1
, rdata: '127.0.0.2'
}
, length: 2
}
}

## ndns.Server

Expand Down Expand Up @@ -114,16 +114,16 @@ passed as the second argument to the 'request' event.
Sets the response header to the request.

Example #1:
response.setHeader(request.header);
response.header.qr = 1;
response.header.qa = 1;
response.setHeader(request.header);
response.header.qr = 1;
response.header.qa = 1;

Example #2:
response.setHeader({
id: 0,
qr: 0,
rd: 1,
qdcount: 1});
response.setHeader({
id: 0,
qr: 0,
rd: 1,
qdcount: 1});

Valid keys `id`, `qr`, `opcode`, `aa`, `tc`, `rd`, `ra`, `z`, `ad`, `cd`,
`rcode`, `qdcount`, `ancount`, `nscount` and `arcount`.
Expand All @@ -132,4 +132,97 @@ This method can be called any number of times and must be called before
`response.send()` is called;

### response.addQuestion(name, class, type)
Sets the question on the response

# Load Balancing

## ndns-nameserver.js

This is a file containing an implementation of a basic DNS nameserver which listens
on port 53 and replies to DNS queries with DNS responses following the DNS protocol
specification.
It also runs an instance of `ndns.poller.server` and `ndns.poller.client` on localhost

### Zone files
Zone files are presently hardcoded into the `ndns-nameserver.js` file in a variable called 'zone'.v
The Zone files are implemented using a tree structure and can be written to using addToTree(tree, branch, records ).
All RR records are stored as an array under a '*' key in the final leaf of the domain tree.

Example #1:
addToTree(zone, ["in","aiesec"],
{ '*' : [
{ name: 'aiesec.in', rr: 'SOA', ttl: '86400', dclass: 'IN', value: 'ns1.bluehost.com. root.box481.bluehost.com. 2011031102 86400 7200 3600000 300'},
{ name: 'aiesec.in', rr: 'TXT', ttl: '14400', dclass: 'IN', value: 'v=spf1 a mx ptr include:bluehost.com ?all' },
{ name: 'aiesec.in', rr: 'NS', ttl: '86400', dclass: 'IN', value: 'ns1.bluehost.com.' },
{ name: 'aiesec.in', rr: 'NS', ttl: '86400', dclass: 'IN', value: 'ns2.bluehost.com.' },
{ name: 'aiesec.in', rr: 'MX', ttl: '14400', dclass: 'IN', value: '0 aiesec.in' },
{ name: 'aiesec.in', rr: 'A', ttl: '14400', dclass: 'IN', value: '74.220.219.81' },
{ name: 'ns1.bluehost.com.', rr: 'A', ttl: '14400', dclass: 'IN', value: '127.0.0.1' },
{ name: 'ns2.bluehost.com.', rr: 'A', ttl: '14400', dclass: 'IN', value: '127.0.0.2' },
] } );

### Round Robin Load Balancing
Round Robin load balancing is achieved by adding the `index` = 0 and `balance` = 'rr' keys to the A record in a domain.
The `value` key should store an array of IPs among which the load will be balanced.
The `name` key can also be a array to facilitate round robin load balancing between nameservers.

Example #1 - Load balancing A records with a constant name:
addToTree(zone, ["ac","in","lnmiit","proxy"],
{ '*' : [
{ name: 'proxy.lnmiit.ac.in', rr: 'A', ttl: '14400', dclass: 'IN' value: ['172.22.2.211',
'172.22.2.212'], index: 0, balance: 'rr' }
]
});
Example #2 - Load balancing NS records with different names:
addToTree(zone, ["com","google"],
{ '*' : [
{ name: ['ns1.google.com',
'ns2.google.com',
'ns3.google.com',
'ns4.google.com'], rr: 'NS', ttl: '14400', dclass: 'IN', value: ['216.239.32.10',
'216.239.34.10',
'216.239.36.10',
'216.239.38.10'], index: 0, balance: 'rr' }
]
} );

### Dynamic Load Balancing
Dynamic load balancing is achieved by adding the `balance` = 'dyn' key to the A record in a domain.
The `value` key should store an array of IPs among which the load will be balanced.

Note : The servers whose IPs are mentioned should be running an instance of `ndns.poller.client` or the load balancing
will default to round robin.

Example #1:
addToTree(zone, ["in","aiesec"],
{ '*' : [
{ name: 'aiesec.in', rr: 'SOA', ttl: '86400', dclass: 'IN', value: 'ns1.bluehost.com. root.box481.bluehost.com. 2011031102 86400 7200 3600000 300'},
{ name: 'aiesec.in', rr: 'TXT', ttl: '14400', dclass: 'IN', value: 'v=spf1 a mx ptr include:bluehost.com ?all' },
{ name: 'aiesec.in', rr: 'NS', ttl: '86400', dclass: 'IN', value: 'ns1.bluehost.com.' },
{ name: 'aiesec.in', rr: 'NS', ttl: '86400', dclass: 'IN', value: 'ns2.bluehost.com.' },
{ name: 'aiesec.in', rr: 'MX', ttl: '14400', dclass: 'IN', value: '0 aiesec.in' },
{ name: 'aiesec.in', rr: 'A', ttl: '14400', dclass: 'IN', value: ['74.220.219.81',
'74.220.219.82',
'127.0.0.1',
'127.0.0.2'] , balance: 'dyn' }, // Dynamic Load Balancingi
{ name: 'ns1.bluehost.com.', rr: 'A', ttl: '14400', dclass: 'IN', value: '127.0.0.1' },
{ name: 'ns2.bluehost.com.', rr: 'A', ttl: '14400', dclass: 'IN', value: '127.0.0.2' },
] } );


## ndns.poller.server.createServer ( POLL_PORT )
This function creates a server which listens on a port (default 5000) for UDP packets from `ndns.poller.client`.
It maintains a list of the IP addresses of the fastest webservers within a particular domain.

Example #1:
var ndns = require('../lib/ndns');
ndns.poller.server.createServer (5000);


## ndns.poller.client.startPoller ( server_host, server_port, domain_name)
This function create a client which sends UDP packet updates to `ndns.poller.server`.

Example #1:
var ndns = require('../lib/ndns');
ndns.poller.client.startPoller ( '127.0.0.1', 5000, 'google.com' );

0 lib/ndns-poller-dispatcher.js → lib/ndns-nameserver.js
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