odbtest/test/gossip

Increment-only counter

This example implements an in-memory incremental-only counter. This is a state-based CRDT, so the write operation is incr().

Demo

Start several peers on the same host. Tell the second and subsequent peers to connect to the first one.

$ ./increment-only-counter -hwaddr 00:00:00:00:00:01 -nickname a -mesh :6001 -http :8001 &
$ ./increment-only-counter -hwaddr 00:00:00:00:00:02 -nickname b -mesh :6002 -http :8002 -peer 127.0.0.1:6001 &
$ ./increment-only-counter -hwaddr 00:00:00:00:00:03 -nickname c -mesh :6003 -http :8003 -peer 127.0.0.1:6001 &

Get current value using the HTTP API of any peer.

$ curl -Ss -XGET "http://localhost:8002/"
get => 0

Increameant the value:

$ curl -Ss -XPOST "http://localhost:8003/"
incr => 1

Get current value from another peer:

$ curl -Ss -XGET "http://localhost:8001/"
get => 1

Incremeant again:

$ curl -Ss -XPOST "http://localhost:8002/"
incr => 2

And get current value from a different peer:

> curl -Ss -XGET "http://localhost:8003/"
get => 2

Implementation

• The state object implements GossipData.
• The peer object implements Gossiper.
• The func main wires the components together.