consistent-hashing-demo

README

Consistent Hashing Demo

A simple demo of consistent hashing.

Features

These features have been implemented:

• Core consistent-hashing-algorithm
• Consistent Hashing with Bounded Loads, according to Consistent Hashing with Bounded Loads
• Customize hash function support
• Customize replica number on hash ring support
• A simple load-balance proxy demo
• A full demo to show how consistent-hashing-algorithm works

How to use

Step 1: Start Server

First, start the proxy server:

$ go run main.go

start proxy server: 18888

This will start the proxy server on port 18888.

The server will listen for incoming registration and will forward key searching to the servers.

Then, start the k-v server:

$ go run server/main.go

start server: 8080

Also, the server will register to the proxy server:

register host: localhost:8080 success

Notice: you can register multiple servers to the proxy server:

go run server/main.go -p 8081
go run server/main.go -p 8082
……

Step 2: Query

Use curl to get the key from proxy：

$ curl localhost:18888/key?key=123

key: 123, val: hello: 123

If you query the key at the first time，the key will be cached on the corresponding server for 10s.

The log for proxy server:

Response from host localhost:8080: hello: 123

The log for k-v server:

cached key: {123: hello: 123}
removed cached key after 3s: {123: hello: 123}

Step 3: Try Query Different Key

You can try to query different key, to check whether they are cached on the different servers:

Response from host localhost:8082: hello: 45363456
Response from host localhost:8080: hello: 4
Response from host localhost:8082: hello: 1
Response from host localhost:8080: hello: 2
Response from host localhost:8082: hello: 3
Response from host localhost:8080: hello: 4
Response from host localhost:8082: hello: 5
Response from host localhost:8080: hello: 6
Response from host localhost:8082: hello: sdkbnfoerwtnbre
Response from host localhost:8082: hello: sd45555254tg423i5gvj4v5
Response from host localhost:8081: hello: 0
Response from host localhost:8082: hello: 032452345

Step 4: Consistent Hash with Load Bound Test

You can request for localhost:18888/key_least for Load Bound testing:

$ curl localhost:18888/key_least?key=123
key: 123, val: hello: 123

the result is shown below:

start proxy server: 18888
register host: localhost:8080 success
register host: localhost:8081 success
register host: localhost:8082 success

Response from host localhost:8080: hello: 123
Response from host localhost:8080: hello: 123
Response from host localhost:8082: hello: 123
Response from host localhost:8082: hello: 123
Response from host localhost:8081: hello: 123
Response from host localhost:8080: hello: 123
Response from host localhost:8082: hello: 123
Response from host localhost:8081: hello: 123
Response from host localhost:8080: hello: 123
Response from host localhost:8082: hello: 123
Response from host localhost:8081: hello: 123
Response from host localhost:8080: hello: 123
Response from host localhost:8082: hello: 123
Response from host localhost:8081: hello: 123
Response from host localhost:8080: hello: 123
Response from host localhost:8080: hello: 123
Response from host localhost:8082: hello: 123
Response from host localhost:8080: hello: 123
Response from host localhost:8082: hello: 123
Response from host localhost:8082: hello: 123

You can see that, Consistent Hash with Load Bound is far more average!

You can change the loadBoundFactor for more experiments:

var (
	// the default number of replicas
	defaultReplicaNum = 10

	// the load bound factor
	// ref: https://research.googleblog.com/2017/04/consistent-hashing-with-bounded-loads.html
	loadBoundFactor = 0.25
	......
)

Reference

Reference:

• https://segmentfault.com/a/1190000041268497
• https://zh.wikipedia.org/wiki/%E4%B8%80%E8%87%B4%E5%93%88%E5%B8%8C
• https://ai.googleblog.com/2017/04/consistent-hashing-with-bounded-loads.html
• https://pkg.go.dev/crypto/sha512#Sum512

Linked Blog:

• 一致性Hash算法总结与应用