# 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](/examples/increment-only-counter/state.go) implements `GossipData`.
- [The peer object](/examples/increment-only-counter/peer.go) implements `Gossiper`.
- [The func main](/examples/increment-only-counter/main.go) wires the components together.