node-modules/cluster-client

Name: cluster-client

Owner: node_modules

Description: Sharing Connection among Multi-Process Nodejs

Created: 2016-12-12 03:03:39.0

Updated: 2018-05-21 17:39:06.0

Pushed: 2018-05-03 03:33:48.0

Homepage: null

Size: 121

Language: JavaScript

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README

cluster-client

Sharing Connection among Multi-Process Nodejs

As we know, each Node.js process runs in a single thread. Usually, we split a single process into multiple processes to take advantage of multi-core systems. On the other hand, it brings more system overhead, sush as maintaining more TCP connections between servers.

This module is designed to share connections among multi-process Nodejs.

Theory

• Inspired by Leader/Follower pattern.
• Allow ONLY one process “the Leader” to communicate with server. Other processes “the Followers” act as “Proxy” client, and forward all requests to Leader.
• The Leader is selected by “Port Competition”. Every process try to listen on a certain port (for example 7777), but ONLY one can occupy the port, then it becomes the Leader, the others become Followers.
• TCP socket connections are maintained between Leader and Followers. And I design a simple communication protocol to exchange data between them.
• If old Leader dies, one of processes will be selected as the new Leader.

Diagram

normal (without using cluster client)

-----+   +--------+
ient |   | Client |   ...
-----+   +--------+
|  \     /   |
|    \ /     |
|    / \     |
|  /     \   |
-----+   +--------+
rver |   | Server |   ...
-----+   +--------+

using cluster-client

         +-------+
         | start |
         +---+---+
             |
    +--------+---------+
  __| port competition |__
/   +------------------+  \ lose
                           \
-----+     tcp conn     +----------+
ader |<---------------->| Follower |
-----+                  +----------+
|
-----+
ient |
-----+
|  \
|    \
|      \
|        \
-----+   +--------+
rver |   | Server |   ...
-----+   +--------+

Protocol

• Packet structure

      1       2               4                                                              12
  ----+-------+---------------+---------------------------------------------------------------+
  sion|req/res|    reserved   |                          request id                           |
  ----------------------------+-------------------------------+-------------------------------+
          timeout             |   connection object length    |   application object length   |
  ----------------------------+---------------------------------------------------------------+
        conn object (JSON format)  ...                    |            app object             |
  --------------------------------------------------------+                                   |
                                         ...                                                  |
  --------------------------------------------------------------------------------------------+
  

• Protocol Type
• Register Channel
• Subscribe/Publish
• Invoke
• Sequence diagram

--------+             +---------------+          +---------+
ollower |             |  local server |          |  Leader |
--------+             +---------------+          +---------+
  |     register channel     |       assign to        |
  + -----------------------> |  --------------------> |
  |                          |                        |
  |                                subscribe          |
  + ------------------------------------------------> |
  |       subscribe result                            |
  | <------------------------------------------------ +
  |                                                   |
  |                                 invoke            |
  + ------------------------------------------------> |
  |          invoke result                            |
  | <------------------------------------------------ +
  |                                                   |

Install

m install cluster-client --save

Node.js >= 6.0.0 required

Usage

 strict';

t co = require('co');
t Base = require('sdk-base');
t cluster = require('cluster-client');


lient Example

s YourClient extends Base {
nstructor(options) {
super(options);

this.options = options;
this.ready(true);


bscribe(reg, listener) {
// subscribe logic


blish(reg) {
// publish logic


getData(id) {
// invoke api


tDataCallback(id, cb) {
// ...


tDataPromise(id) {
// ...



reate some client instances, but only one instance will connect to server
t client_1 = cluster(YourClient)
elegate('getData')
elegate('getDataCallback')
elegate('getDataPromise')
reate({ foo: 'bar' });
t client_2 = cluster(YourClient)
elegate('getData')
elegate('getDataCallback')
elegate('getDataPromise')
reate({ foo: 'bar' });
t client_3 = cluster(YourClient)
elegate('getData')
elegate('getDataCallback')
elegate('getDataPromise')
reate({ foo: 'bar' });

ubscribe information
nt_1.subscribe('some thing', result => console.log(result));
nt_2.subscribe('some thing', result => console.log(result));
nt_3.subscribe('some thing', result => console.log(result));

ublish data
nt_2.publish('some data');

nvoke method
nt_3.getDataCallback('some thing', (err, val) => console.log(val));
nt_2.getDataPromise('some thing').then(val => console.log(val));

unction*() {
nst ret = yield client_1.getData('some thing');
nsole.log(ret);
atch(err => console.error(err));

API

• delegate(from, to): create delegate method, from is the method name your want to create, and to have 6 possible values: [ subscribe, unSubscribe, publish, invoke, invokeOneway, close ], and the default value is invoke
• override(name, value): override one property
• create(?) create the client instance
• close(client) close the client
• APIClientBase a base class to help you create your api client

Best Practice

1. DataClient
2. Only provider data API, interact with server and maintain persistent connections etc.
3. No need to concern cluster issue
4. APIClient
5. Using cluster-client to wrap DataClient
6. Put your bussiness logic here

DataClient

t Base = require('sdk-base');

s DataClient extends Base {
nstructor(options) {
super(options);
this.ready(true);


bscribe(info, listener) {
// subscribe data from server


blish(info) {
// publish data to server


getData(id) {
// asynchronous API

APIClient

t DataClient = require('./your-data-client');
t { APIClientBase } = require('cluster-client');

s APIClient extends APIClientBase {
nstructor(options) {
super(options);
this._cache = new Map();

t DataClient() {
return DataClient;

t delegates() {
return {
  getData: 'invoke',
};

t clusterOptions() {
return {
  name: 'MyClient',
};

bscribe(...args) {
return this._client.subscribe(...args);

blish(...args) {
return this._client.publish(...args);

getData(id) {
// write your business logic & use data client API
if (this._cache.has(id)) {
  return this._cache.get(id);
}
const data = yield this._client.getData(id);
this._cache.set(id, data);
return datal

s
---------------------------------------------|
IClient                                      |
    |----------------------------------------|
    | ClusterClient                          |
    |      |---------------------------------|
    |      | DataClient                      |
----|------|---------------------------------|

For more information, you can refer to the discussion

MIT