# Weave Net and Docker Swarm

This example show how-to setup a very simple Swarm cluster enabled with Weave Net.

## Infratructure

There are two hosts that have a recent version of Docker Engine running.

These hosts are named `host1` and `host2`, and might have the following in
`/etc/hosts` or you just substitute IP addresses in the commands shown below.


```
192.168.131.139   host1
192.168.131.140   host2
```

## Install and launch Weave Net

To install Weave Net run the following commands on each of the hosts
```
sudo curl --silent --location git.io/weave --output /usr/local/bin/weave
chmod +x /usr/local/bin/weave
```

Now start the router on each of the host with
```
weave luanch-router host1 host2
```

Proxy needs to be launched with the following arguments
```
weave launch-proxy -H 0.0.0.0:12375 --no-detect-tls

```

> You can omit `--no-detect-tls`, but in that case you might wish to omit
> all of the arugments. If so, you will need to ensure that TLS keys are
> in all the right places.

## Launch Swarm manger

Swarm manager can run very simply like this agains two of the host that
run Weave Net and the Docker API proxy is listening on port 12375:

```
docker run -d -p 2377:2375 swarm manage nodes://host1:12375,host2:12375
```

> If you would like to use a different discovery mechanism, you can do this
> but then you will need run Swarm agents on each of the hosts and ensure
> that those are pointed at the address the proxy is listening on. This
> would typically mean `swarm join --addr <ip>:12375 <discovery>`.

## Ping Me, I am on Weave Net!

Let's start 20 containers via Swarm, on the same host the manager is running.
```
for i in $(seq 20)
do docker -H 127.0.0.1:2377 run -td --name="pingme-${i}" --hostname="pingme.weave.local" centos:7
done
```

Check `weave status dns` and you will see there are 20 entries now. You can also
do a lookup with `weave dns-lookup pingme` a few times and see that shuffled IPs
are being returned each time.

Next, let's run the ping test like this:
```
$ docker -H 127.0.0.1:2377 run -ti centos:7
[root@4a73489ae22e /]# ping -c1 pingme
PING pingme.weave.local (10.40.0.5) 56(84) bytes of data.
64 bytes from pingme.weave.local (10.40.0.5): icmp_seq=1 ttl=64 time=1.12 ms

--- pingme.weave.local ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 1.128/1.128/1.128/0.000 ms
[root@4a73489ae22e /]# ping -c1 pingme
PING pingme.weave.local (10.40.0.2) 56(84) bytes of data.
64 bytes from pingme.weave.local (10.40.0.2): icmp_seq=1 ttl=64 time=9.34 ms

--- pingme.weave.local ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 9.345/9.345/9.345/0.000 ms
[root@4a73489ae22e /]# ping -c1 pingme
PING pingme.weave.local (10.32.0.1) 56(84) bytes of data.
64 bytes from pingme.weave.local (10.32.0.1): icmp_seq=1 ttl=64 time=0.166 ms

--- pingme.weave.local ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.166/0.166/0.166/0.000 ms
[root@4a73489ae22e /]# ping -c1 pingme
PING pingme.weave.local (10.32.0.8) 56(84) bytes of data.
64 bytes from pingme.weave.local (10.32.0.8): icmp_seq=1 ttl=64 time=0.162 ms

--- pingme.weave.local ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.162/0.162/0.162/0.000 ms
[root@4a73489ae22e /]# ping -c1 pingme
PING pingme.weave.local (10.40.0.4) 56(84) bytes of data.
64 bytes from pingme.weave.local (10.40.0.4): icmp_seq=1 ttl=64 time=0.987 ms

--- pingme.weave.local ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.987/0.987/0.987/0.000 ms
[root@4a73489ae22e /]# exit
```

Now, just to convince yourself, run `docker -H 127.0.0.1:2377 ps` to check that all
of these 20 containers are on different hosts.