Turdus is a client side HTTP Round-robin and Weighted round-robin load balancing library.
It provides following features:
- Client side Load balancing
- Fault tolerance
- Normalized Response on request failure.
- Mutiple apps supported.
For simple Round-robin, it is basically array loop.
For weighted round robin algorithm, on each peer selection we increase current_weight of each eligible peer by its weight, select peer with greatest current_weight and reduce its current_weight by total number of weight points distributed among peers.
see also: nginx implementation
[Deprecated] For weighted round robin algorithm (gcd version):
- calculate GCD of all endpoints' weight
- choose the max weighted endpoint then minus GCD
- if largest weight belongs to more than one endpoint, choose the small index one.
- set to original weight until no weight bigger than zero.
- repeat the procedures above.
install turdus by npm.
npm install turdus
Provide or fetch your callee apps' IP/domain from written configs
or subscribe event by eureka client and fetchRegistry from Eureka
- simple polling each server.
const Turdus = require('turdus');
// initialize multiple app
const trudus = Turdus({
bird: ['127.0.0.1', '127.0.0.2', '127.0.0.3'],
kitten: ['192.168.0.1', '192.168.0.2', '192.168.0.3'],
});
async function touchServer() {
await turdus.request('bird', {
method: 'GET',
uri: '/cat-books',
});
}
touchServer();
touchServer();
touchServer();
// ...
// will touch known resources one by one.
//
// curl http://127.0.0.1/cat-books
// curl http://127.0.0.2/cat-books
// curl http://127.0.0.3/cat-books
// curl http://127.0.0.1/cat-books
// curl http://127.0.0.2/cat-books
// curl http://127.0.0.3/cat-books
// ...- weighted polling each servers;
const Turdus = require('turdus');
const turdus = Turdus({ bird: [
{ server: '127.0.0.1', weight: 5 },
{ server: '127.0.0.2', weight: 10 },
{ server: '127.0.0.3', weight: 4 },
]});
async function touchServer() {
await turdus.request('bird', {
method: 'GET',
uri: '/cat-books',
});
}
touchServer();
touchServer();
touchServer();
// ...
// will touch known resources by their weight.
//
// curl http://127.0.0.2/cat-books
// curl http://127.0.0.1/cat-books
// curl http://127.0.0.3/cat-books
// curl http://127.0.0.2/cat-books
// curl http://127.0.0.2/cat-books
// curl http://127.0.0.1/cat-books
// curl http://127.0.0.2/cat-books
// curl http://127.0.0.3/cat-books
// curl http://127.0.0.2/cat-books
// curl http://127.0.0.1/cat-books
// curl http://127.0.0.2/cat-books
// curl http://127.0.0.3/cat-books
// curl http://127.0.0.2/cat-books
// curl http://127.0.0.1/cat-books
// curl http://127.0.0.2/cat-books
// curl http://127.0.0.2/cat-books
// curl http://127.0.0.3/cat-books
// curl http://127.0.0.1/cat-books
// curl http://127.0.0.2/cat-books
// ...- fault tolerance and nomalize error response.
const turdus = Turdus({ bird: [ '127.0.0.1', '127.0.0.2' ] });
turdus.fakePositiveRes('bird', {
'/cat-birds': 'though some error appeared',
'/cat-books': [ 'The Fountainhead', 'Poor Charlie's Almanack:The Wit and Wisdom of Charles T. Munger', 'The Little Prince' ],
});
turdus.request('bird', {
uri: '/cat-birds',
method: 'POST',
body: { yy: 6 },
json: true,
})
.then((result) => {
// though enpoints is not touchable
// we can get positive response due to preset method.
// result.statusCode: 200
// result.body: 'though some error appeared',
});- update exist applications' endpoints or add new applications.
const endpoints = {
kitten: [
{ server: '127.0.0.1', weight: 0 },
{ server: '127.0.0.2', weight: 0 },
],
doggy: [
{ server: '192.168.0.1', weight: 0 },
{ server: '192.168.0.2', weight: 0 },
],
};
const turdus = Turdus(endpoints);
turdus.upsertEndpoints({
doggy: [
{ server: '192.168.0.1', weight: 3 },
{ server: '192.168.0.2', weight: 3 },
{ server: '192.168.0.3', weight: 1 },
{ server: '192.168.0.4', weight: 1 },
],
});
// the doggy application's endpoints will be changed.
// also it's balance type got changed from raw to weighted.NOTE: this function may reset related applications' current polling order to original status.
MIT