Weave Net

Launching Weave Net

Weave Net provides a simple to deploy networking solution for containerized apps. Here, we describe how to manage a Weave container network using a sample application which consists of two simple netcat services deployed to containers on two separate hosts.

This section contains the following topics:

Launching Weave Net

Before launching Weave Net and deploying your apps, ensure that Docker is installed on both hosts.

On $HOST1 run:

host1$ weave launch
host1$ eval $(weave env)
host1$ docker run --name a1 -ti alpine:latest

Where,

Note If the first command results in an error like

Cannot connect to the Docker daemon. Is the docker daemon running on this host?

or

http:///var/run/docker.sock/v1.19/containers/create: dial unix/var/run/docker.sock: permission denied. Are you trying to connect to a TLS-enabled daemon without TLS?

then you likely need to be ‘root’ in order to connect to the Docker daemon. If so, run the above and all subsequent commands in a single root shell:

host1$ sudo -s
host1# weave launch
host1# eval $(weave env)
host1# docker run --name a1 -ti alpine:latest

Do not prefix individual commands with sudo, since some commands modify environment entries and hence they all need to be executed from the same shell.

Weave Net must be launched once per host. The relevant container images will be pulled down from Docker Hub on demand during weave launch.

You can also preload the images by running weave setup. Preloaded images are useful for automated deployments, and ensure there are no delays during later operations.

If you are deploying an application that consists of more than one container to the same host, launch them one after another using docker run, as appropriate.

Creating Peer Connections Between Hosts

To launch Weave Net on an additional host and create a peer connection, run the following:

host2$ weave launch $HOST1
host2$ eval $(weave env)
host2$ docker run --name a2 -ti alpine:latest

As noted above, the same steps are repeated for $HOST2. The only difference, besides the application container’s name, is that $HOST2 is told to peer with Weave Net on $HOST1 during launch.

You can also peer with other hosts by specifying the IP address, and a :port by which $HOST2 can reach $HOST1.

Note: If there is a firewall between $HOST1 and $HOST2, you must permit traffic to flow through TCP 6783 and UDP 6783/6784, which are Weave’s control and data ports.

There are a number of different ways that you can specify peers on a Weave network. You can launch Weave Net on $HOST1 and then peer with $HOST2, or you can launch on $HOST2 and peer with $HOST1 or you can tell both hosts about each other at launch. The order in which peers are specified is not important. Weave Net automatically (re)connects to peers when they become available.

Specifying Multiple Peers at Launch

To specify multiple peers, supply a list of addresses to which you want to connect, all separated by spaces.

For example:

host2$ weave launch <ip address> <ip address>

Peers can also be dynamically added. See Adding Hosts Dynamically for more information.

Restricting Access

By default Weave Net listens on all host IPs (i.e. 0.0.0.0). This can be altered with the --host parameter to weave launch, for example, to ensure that Weave Net only listens on IPs on an internal network.

Standard firewall rules can be deployed to restrict access to the Weave Net control and data ports.

For communication across untrusted networks, connections can be encrypted.

Testing Container Communications

With two containers running on separate hosts, test that both containers are able to find and communicate with one another using ping.

From the container started on $HOST1…

root@a1:/# ping -c 1 -q a2
PING a2.weave.local (10.40.0.2) 56(84) bytes of data.
--- a2.weave.local ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.341/0.341/0.341/0.000 ms

Similarly, in the container started on $HOST2…

root@a2:/# ping -c 1 -q a1
PING a1.weave.local (10.32.0.2) 56(84) bytes of data.
--- a1.weave.local ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.366/0.366/0.366/0.000 ms

Starting the Netcat Service

The netcat service can be started using the following commands:

root@a1:/# nc -lk -p 4422

and then connected to from the another container on $HOST2 using:

root@a2:/# echo 'Hello, world.' | nc a1 4422

Weave Net supports any protocol, and it doesn’t have to be over TCP/IP. For example, a netcat UDP service can also be run by using the following:

root@a1:/# nc -lu -p 5533
root@a2:/# echo 'Hello, world.' | nc -u a1 5533

See Also