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https://github.com/la3rence/websocket-cluster

一致性哈希实现有状态应用集群。Scalable spring-cloud project for WebSocket cluster with consistent-hashing algorithm. (inactive)
https://github.com/la3rence/websocket-cluster

consistent-hashing distributed-systems docker gateway-microservice hashring nacos rabbitmq redis spring-cloud spring-cloud-gateway springcloud websocket websocket-cluster

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一致性哈希实现有状态应用集群。Scalable spring-cloud project for WebSocket cluster with consistent-hashing algorithm. (inactive)

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README 

        
# WebSocket Cluster (Spring Cloud) in action



This is a Spring Cloud project for WebSocket cluster servers.



[中文](README.md)



## Principle



Using a consistent hashing algorithm, we construct a hash ring where the gateway listens to the up and down event of the

WebSocket service instances and dynamically updates the hash ring according to the changes of the instances. Each time a

new service comes online, the corresponding virtual node is added, and the WebSocket clients that need to change are

reconnected to the new instance. Clients that need to be changed are reconnected to the new instance, which is the least

expensive; of course, it also depends on the count of the virtual nodes and the fairness of the hashing algorithm. When

the service goes offline, it is easier -- just disconnect all clients from the current instance, and the clients will

always reconnect. At the same time, the core role of the hash ring is reflected in the load balancing. When the gateway

does its request forwarding, it goes through our rewritten custom load balancing filter, which implements real node

routing based on the fields that need to be hashed for business purposes.



## Middleware / Environment Preparation



- Docker (with API accessible)

- Redis

- RabbitMQ

- Nacos



## Development



Create a docker-compose network for [docker-compose.yml](./docker-compose.yml):



```shell

docker network create compose-network

```



Local build and deploy by docker-compose:



```shell

mvn clean

mvn install -pl gateway -am -amd

mvn install -pl websocket -am -amd

docker build -t websocket:1.0.0 websocket/.

docker build -t gateway:1.0.0 gateway/.

docker-compose up -d

docker ps

```



Scale the websocket instance by: `docker-compose scale websocket-server=3`. Actually, I wrote a front-end web page to

start a new instance for websocket service.



Don't forget to enable the docker remote api (e.g., check out `docker -H tcp://0.0.0.0:2375 ps`):

The following steps may help:



### Access docker API on Linux



Append `-H tcp://0.0.0.0:2375` to the line started of `ExecStart` in the file named `docker.service`



```shell

# cat /usr/lib/systemd/system/docker.service

ExecStart=...... -H tcp://0.0.0.0:2375

# after saved, restart the docker process

systemctl daemon-reload

systemctl restart docker

```



### Access docker API on macOS



The best practice is using the image `alpine/socat` to expose a tcp socket. (

see: [usage of socat](https://github.com/alpine-docker/socat#example)).



```shell

docker run -itd --name socat \

    -p 0.0.0.0:6666:2375 \

    -v /var/run/docker.sock:/var/run/docker.sock \

    alpine/socat \

    tcp-listen:2375,fork,reuseaddr unix-connect:/var/run/docker.sock

```



For the record, the Docker-desktop client for macOS provides the `docker.for.mac.host.internal` hostname for accessing

the host in the container of docker. I also add this domain to my `/etc/hosts` and point it to the localhost address. So

I use this address in `application.yml` to set up configuration for the redis, the rabbitmq and the nacos servers(they

are all deployed in the container). You can change this address if you deploy on your machine or other linux servers.

BTW, the Makefile is only for self usage, which makes me build and restart the service faster during the development

phase because I didn't prepare a CI/CD pipeline for this project. Please use it as needed.



## Front-end



Check out [this react app](https://github.com/Lonor/websocket-cluster-front). It looks like:



![Demo](./demo.gif)



## Contribution



If this project helps, please star it. Submit an issue if you have any question. You can contribute code by forking this

project and submit your Pull Request.