TCP Server

TCP server written in Go.

Usage

1. Download go
2. Download the program go get git github.com/shavit/laughing_fortnight
3. Build go build github.com/shavit/laughing_fortnight/cmd/
4. Run ./cmd

Server

The server echos back messages. To start the server:

./cmd server

This will start a TCP server that will accept connections on 2 ports, from both CLI clients and other nodes.

Client

The client that included in this program will try to print out the messages as string, but you can comment out the print command and rebuild the client.

To start the client:

$ ./cmd client

In the event of election, the client will reconnect to the leader and will continue to send and receive messagse.

Nodes

The server will hold a list of the other nodes in the network. Each node will try to connect first to the master node, in a known address.

A new node connection will make a request for all the available nodes in the network.

To run as a node:

./cmd -p PORT server

The node will ignore the port and host arguments if there is no master.

Reconnect as a master

When the server dies, the oldest node or the last node, will take the master port and restart the connection.

When the slave becomes a master it will only establish a TCP connection to the other nodes. The client will lose the connection.

Election

In this example the nodes do not communicate with each other, and there is no scoring system or health checks on each node.

etcd

etcd is a reliable key value store that will be used here for the leader election.

To install etcd, glone the project using git and run the following commands

$ git clone https://github.com/coreos/etcd.git $GOPATH/github.com/coreos/etcd
$ cd $GOPATH/github.com/coreos/etcd
$ go get ./...
$ ./build
$ export PATH=$PATH:$GOPATH/src/github.com/coreos/etcd/bin

Start etcd and pass an address to advertise

$ etcd --advertise-client-urls http://localhost:2379

Leader Election Example

Start 3 servers, or any odd number for leader election. The server with the 8888 port starts as a leader.

1$ ./cmd -p 8888 server
2$ ./cmd -p 9700 server
3$ ./cmd -p 9800 server

The servers can start without a port assigned to them.

1$ ./cmd server
2$ ./cmd server
3$ ./cmd server

These servers will connect to the etcd at 127.0.0.1:2379, or the value that was passed to the -endpoint flag.

When the election is complete the leader will restart and listen to port 8888.