raft-chat

raft-chat is an highly-available chat server not requiring any databases. It is backed by the Raft consensus algorithm.

Features

• No database required
• Rooms and Messages
• Unlimited retention of messages
• Basic Web client
• REST API support
• Websocket support
• Easy to backup (file only)
• Support non-voting followers
• Identity and Login support
• Pagination (of messages and rooms)
• Websocket robustness (ping/ping and reconnections)
• Limit persistence of rooms and messages
• Truncate empty rooms

Getting Started

Running single node raft-chat

First start a single-member cluster of raft-chat:

raft-chat --id 1 --cluster http://127.0.0.1:12379 --port 12380

Each raft-chat process maintains a single raft instance and a chat server. The process's list of comma separated peers (--cluster), its raft ID index into the peer list (--id), and http API server port (--port) are passed through the command line.

Next, post a message ("hello") to a room ("general"):

curl -L http://127.0.0.1:12380/rooms/general -d '{"Message": "hello", "User": "username"}'

Next, retrieve the stored messages of a room:

curl -L http://127.0.0.1:12380/rooms/general

Finally, retrieve the list of rooms:

curl -L http://127.0.0.1:12380/rooms

Running a local cluster

This will bring up three raft-chat instances.

raft-chat --id 1 --cluster http://127.0.0.1:12379,http://127.0.0.1:22379,http://127.0.0.1:32379 --port 12380
raft-chat --id 2 --cluster http://127.0.0.1:12379,http://127.0.0.1:22379,http://127.0.0.1:32379 --port 22380
raft-chat --id 3 --cluster http://127.0.0.1:12379,http://127.0.0.1:22379,http://127.0.0.1:32379 --port 32380

Now it's possible to send messages to any member of the cluster and likewise retrieve it from any member.

Fault Tolerance

To test cluster recovery, first start a cluster and write a message "foo" to room "general":

curl -L http://127.0.0.1:12380/rooms/general -d '{"Message": "foo", "User": "username"}'

Next, remove a node and add another message with "bar" to check cluster availability:

# stop node 1
curl -L http://127.0.0.1:22380/rooms/general -d '{"Message": "bar", "User": "username"}'

Finally, bring the node back up and verify it has a "general" chat room with the "bar" message:

# start node 1
curl -L http://127.0.0.1:12380/general

Dynamic cluster reconfiguration

Nodes can be added to or removed from a running cluster using requests to the REST API.

For example, suppose we have a 3-node cluster that was started with the commands:

# start node 1
raft-chat --id 1 --cluster http://127.0.0.1:12379,http://127.0.0.1:22379,http://127.0.0.1:32379 --port 12380
raft-chat --id 2 --cluster http://127.0.0.1:12379,http://127.0.0.1:22379,http://127.0.0.1:32379 --port 22380
raft-chat --id 3 --cluster http://127.0.0.1:12379,http://127.0.0.1:22379,http://127.0.0.1:32379 --port 32380

A fourth node with ID 4 can be added by issuing a POST:

curl -L http://127.0.0.1:12380/raft/4 -d http://127.0.0.1:42379

Then the new node can be started as the others were, using the --join option:

raft-chat --id 4 --cluster http://127.0.0.1:12379,http://127.0.0.1:22379,http://127.0.0.1:32379,http://127.0.0.1:42379 --port 42380 --join

The new node should join the cluster and be able to service chat requests.

We can remove a node using a DELETE request:

curl -L http://127.0.0.1:12380/raft/3 -X DELETE

Node 3 should shut itself down once the cluster has processed this request.