Docker versions 1.9 and later have a plugin mechanism for adding different network providers. Weave Net installs itself as a network plugin when you start it with weave launch. The Weave Docker Networking Plugin is fast and easy to use, and, unlike other networking plugins, does not require an external cluster store.

To create a network which can span multiple Docker hosts, Weave Net peers must be connected to each other, by specifying the other hosts during weave launch or via weave connect.

See Using Weave Net for a discussion on peer connections.

After you’ve launched Weave Net and peered your hosts, you can start containers using the following, for example:

$ docker run --net=weave -ti weaveworks/ubuntu

on any of the hosts, and they can all communicate with each other using any protocol, even multicast.

In order to use Weave Net’s Service Discovery you must pass the additional arguments --dns and -dns-search, for which a helper is provided in the Weave script:

$ docker run --net=weave -h foo.weave.local $(weave dns-args) -tdi weaveworks/ubuntu
$ docker run --net=weave -h bar.weave.local $(weave dns-args) -ti weaveworks/ubuntu
# ping foo

Launching Weave Net and Running Containers Using the Plugin

Just launch the Weave Net router onto each host and make a peer connection with the other hosts:

host1$ weave launch host2
host2$ weave launch host1

then run your containers using the Docker command-line:

host1$ docker run --net=weave -ti weaveworks/ubuntu
root@1458e848cd90:/# hostname -i
10.32.0.2

host2$ docker run --net=weave -ti weaveworks/ubuntu
root@8cc4b5dc5722:/# ping 10.32.0.2

PING 10.32.0.2 (10.32.0.2) 56(84) bytes of data.
64 bytes from 10.32.0.2: icmp_seq=1 ttl=64 time=0.116 ms
64 bytes from 10.32.0.2: icmp_seq=2 ttl=64 time=0.052 ms

Creating multiple Docker Networks

Docker enables you to create multiple independent networks and attach different sets of containers to each network. However, coordinating this between hosts requires that you run Docker in “swarm mode” or configure a “key-value store”.

To operate in swarm mode, you are required to use the plugin v2 of Weave Net. See Integrating Docker via the Network Plugin (V2) for more details.

If your Docker installation has a key-value store, create a network based on Weave Net as follows:

$ docker network create --driver=weave mynetwork

then use it to connect a container:

$ docker run --net=mynetwork ...

or

$ docker network connect mynetwork somecontainer

Containers attached to different Docker Networks are isolated through subnets.

Restarting the Plugin

The plugin, like all Weave Net components, is started with a policy of --restart=always, so that it is always there after a restart or reboot. If you remove this container (for example, when using weave reset) before removing all endpoints created using --net=weave, Docker may hang for a long time when it subsequently tries to re-establish communications to the plugin.

Unfortunately, Docker 1.9 may also try to communicate with the plugin before it has even started it.

If you are using systemd with Docker 1.9, it is advised that you modify the Docker unit to remove the timeout on startup. This gives Docker enough time to abandon its attempts. For example, in the file /lib/systemd/system/docker.service, add the following under [Service]:

TimeoutStartSec=0

See Also