gord-overlay

Gord-Overlay

• Gord is a reference implementation of Chord protocol.
• Gord-Overlay is a fork of Gord which is enabled to run on overlay network constructed with gossip-overlay lib
  • Additionaly, offers on-memory KVS store functionality

What is Gord-Overlay?

Gord-Overlay is a DHT based distribute key-value store. Gord-Overlay will start as a REST server and your application can access data via REST.

How is it work?

Gord-Overlay is an implementation of DHT Chord and simple key-value store using the DHT. Chord protocol is an algorithm which extends consistent hashing. Gord-Overlay server, using chord protocol, allocates a key to a node in distributed nodes ring.

In addition, servers communicate with each other via REST to synchronize route information. Then, servers can query via REST to resolve server address and communicate with the server.

Usage

• Gord-Overlay REST server reqires a hostname and port number pair
• If you specify 127.0.0.1:26000, the server will use 127.0.0.1:26000 to communication between other nodes and use 127.0.0.1:26001 to listen local REST request
• Specified hostname and port number pair is internally used as a server identifier, so you need to specify a unique pair for each server
• Additionaly, you need to specify address of a server which is already in the DHT network to join the network except the first server
• Proxy server introduced later section is a utility to connect to the overlay network from outside of the network
  • These connect to bootstrap server. currently, server at ryogrid.net:9999 is hard-coded a
  • But you can change it by modifying this line
  • First proxy can launch with command ./third/gossip-port-forward/gossip-port-forward relay -p listenPort(required)
  • Other proxy can be bootstrap server also. But one proxy which has global IP is needed at least on overlay network for NAT travarsal

## Build
make build

## Build proxy for gordolctl connecting to overlay network
git pull
git submodule init
git submodule update
cd third/gossip-port-forward
go build -o gossip-port-forward gossip-port-forward.go

## Start proxy
./third/gossip-port-forward/gossip-port-forward both -a 127.0.0.1 -f forwardAddress(required) -l listenPort(required)

## Start server
./gordolctl -l hostAndPort(required) -p proxyHostAndPort(required) -n existNodeHostAndPort(optional) 

Examples

1. Start servers

# launch 3 servers (3 shells are needed...)
cp ./third/gossip-port-forward/gossip-port-forward .

# each gordlctl internally launch gossip-port-forward process for myself
./gordolctl -l 127.0.0.1:20000 -p 127.0.0.1:20002
./gordolctl -l 127.0.0.1:20004 -n 127.0.0.1:20000 -p 127.0.0.1:20006
./gordolctl.exe -l 127.0.0.1:20008 -n 127.0.0.1:20004 -p 127.0.0.1:20010

1. Try!

# Query
curl -X POST -H "Content-Type: application/json" -d '{"key": "gord1"}' http://localhost:20001/server.ExternalService/FindHostForKey \
&& curl -X POST -H "Content-Type: application/json" -d '{"key": "gord1"}' http://localhost:20005/server.ExternalService/FindHostForKey \
&& curl -X POST -H "Content-Type: application/json" -d '{"key": "gord1"}' http://localhost:20009/server.ExternalService/FindHostForKey 

curl -X POST -H "Content-Type: application/json" -d '{"key": "gord2"}' http://localhost:20001/server.ExternalService/FindHostForKey \
&& curl -X POST -H "Content-Type: application/json" -d '{"key": "gord2"}' http://localhost:20005 server.ExternalService/FindHostForKey \
&& curl -X POST -H "Content-Type: application/json" -d '{"key": "gord2"}' http://localhost:20009 server.ExternalService/FindHostForKey 

curl -X POST -H "Content-Type: application/json" -d '{"key": "gord"}' localhost:20001 server.ExternalService/FindHostForKey \
&& curl -X POST -H "Content-Type: application/json" -d '{"key": "gord"}' localhost:20005 server.ExternalService/FindHostForKey \
&& curl -X POST -H "Content-Type: application/json" -d '{"key": "gord"}' localhost:20009 server.ExternalService/FindHostForKey

# Put and Get value
curl -X POST -H "Content-Type: application/json" -d '{"key": "hoge", "value": "foobar"}' http://localhost:20001/server.ExternalService/PutValue
curl -X POST -H "Content-Type: application/json" -d '{"key": "hoge"}' http://localhost:20005/server.ExternalService/GetValue
curl -X POST -H "Content-Type: application/json" -d '{"key": "hoge"}' http://localhost:20009/server.ExternalService/GetValue

Development Memo

• here (Japanese)

TODO (not implemented part)

• Easy trial
  • Dockerfile and docker-compose.yml is not updated properly yet...
• Data replication
  • Puted data is stored only one server now
• Abnormal situation handling
  • Servers may crash when a node leavs DHT network or HTTP/2 connection...
• Handling new server join and server leave
  • When join, data delegation should be needed
  • When leave, number of servers which have replica assinged to leaved node should be keeped
    • Data delegation between a server same replica having and new assined node must occur