raft

README

raft cluster

raft cluster is an example usage of raft library. It provides a simple REST API for a key-value store cluster backed by the Raft consensus algorithm.

Getting Started

Building raft cluster example

get raft example

mkdir -p raftexample
cd raftexample
GOBIN=${PWD} go get github.com/franklee0817/raft/_examples/raft

Running single node raft

First start a single-member cluster of raft:

./raft -state_dir=$TMPDIR/1 -raft :8080 -api :9090 

Each raft process maintains a single raft instance and a key-value server. raft server address (-raft), state dir (-state_dir), and http key-value server address (-api) are passed through the command line.

Next, store a value ("world") to a key ("hello"):

curl -L http://127.0.0.1:9090/ -X PUT -d '{"Key":"hello", "Value":"world"}'

Finally, retrieve the stored key:

curl -L http://127.0.0.1:9090/hello

Running a local cluster

Lets bring two additional raft instances.

./raft -state_dir $TMPDIR/2 -raft :8081 -api :9091 -join :8080
./raft -state_dir $TMPDIR/3 -raft :8082 -api :9092 -join :8080

Now it's possible to write a key-value pair to any member of the cluster and likewise retrieve it from any member.

Fault Tolerance

To test cluster recovery, write a value "foo" to key "foo":

curl -L http://127.0.0.1:9090/ -X PUT -d '{"Key":"foo", "Value":"foo"}'

Next, stop a node (9092) and replace the value with "bar" to check cluster availability:

curl -L http://127.0.0.1:9090/ -X PUT -d '{"Key":"foo", "Value":"bar"}'
curl -L http://127.0.0.1:9090/foo

Finally, bring the node back up and verify it recovers with the updated value "bar":

curl -L http://127.0.0.1:9092/foo

cluster reconfiguration

Nodes can be added, removed, updated from a running cluster, lets remove node using requests to the REST API.

First, list all raft cluster nodes, and get node id.

curl -L http://127.0.0.1:9090/mgmt/nodes

Then remove a node using a DELETE request:

curl -L http://127.0.0.1:9090/<ID> -X DELETE

Node will shut itself down once the cluster has processed this request.