weave/site/proxy.md

title, layout

title	layout
Weave Proxy	default

Weave Proxy

The proxy automatically attaches containers to the weave network when they are started using the ordinary Docker command-line interface or remote API, instead of weave run.

• Setup
• Usage
• Automatic IP address assignment
• Automatic discovery
• Multi-host example
• Securing the docker communication with TLS
• Troubleshooting

Setup

The proxy sits between the Docker client (command line or API) and the Docker daemon, intercepting the communication between the two.

To start the proxy, run

host1$ weave launch-proxy

By default, the proxy will connect to docker at unix:///var/run/docker.sock. This can be adjusted with the -H argument, e.g.

host1$ weave launch-proxy -H tcp://127.0.0.1:4243

The proxy listens on port 12375, on all network interfaces. All docker commands can be run via the proxy, so it is safe to globally adjust your DOCKER_HOST to point at the proxy, e.g.

host1$ export DOCKER_HOST=tcp://localhost:12375
host1$ docker ps
...

If you are working with a remote docker daemon, then localhost in the above needs to be replaced with the docker daemon host, and any firewalls inbetween need to be configured to permit access to port 12375.

Usage

When containers are created via the weave proxy, their entrypoint will be modified to wait for the weave network interface to become available. When they are started via the weave proxy, any IP addresses and networks specified in the WEAVE_CIDR environment variable will be attached. We can create and start a container via the weave proxy with

host1$ docker run -e WEAVE_CIDR=10.2.1.1/24 -ti ubuntu

or, equivalently with

host1$ docker create -e WEAVE_CIDR=10.2.1.1/24 -ti ubuntu
5ef831df61d50a1a49272357155a976595e7268e590f0a2c75693337b14e1382
host1$ docker start 5ef831df61d50a1a49272357155a976595e7268e590f0a2c75693337b14e1382

Multiple IP addresses and networks can be supplied in the WEAVE_CIDR variable by space-separating them, as in WEAVE_CIDR="10.2.1.1/24 10.2.2.1/24".

Using the proxy brings some additional benefits over weave run. The proxy ensures that the weave network interface is available before starting a container's application process. Furthermore, containers can be started in foreground mode, and can be automatically removed (with the ususal --rm).

Automatic IP address assignment

If automatic IP address assignment is enabled in weave, e.g. by launching it with

host1$ weave launch -iprange 10.2.3.0/24

then containers started via the proxy can be automatically assigned an IP address by providing a blank WEAVE_CIDR environment variable, as in

host1$ docker run -e WEAVE_CIDR= -ti ubuntu

Furthermore, it is possible to configure the proxy such that all containers started via it are automatically assigned an IP address and attached to weave network, without having to specify any special environment variables or other options. To do this we launch the proxy with the --with-ipam option, e.g.

host1$ weave launch-proxy --with-ipam

Now any container started via the proxy, e.g. with

host1$ docker run -ti ubuntu

gets attached to the weave network with an automatically assigned IP address. Containers started with a WEAVE_CIDR environment variable are handled as before.

Automatic discovery

Containers started via the proxy are automatically registered in weaveDNS if they have a hostname in the weaveDNS domain (usually .weave.local). In order for containers to be able to look up such names, their DNS resolver needs to be configured to point at weaveDNS. This can be done manually, or automatically by the proxy by launching it with the --with-dns option, i.e.

host1$ weave launch-proxy --with-dns

Now any containers started via the proxy, and with a WEAVE_CIDR=... environment variable (or even without it, if IPAM is configured), will use weaveDNS for name resolution.

Multi-host example

Here's a complete example of using weave proxies configured with automatic IP address assignment and automatic discovery to start containers on two hosts such that they can reach each other by name.

First, let us start weave, weaveDNS and the proxy, and set DOCKER_HOST to point at the latter:

host1$ weave launch -iprange 10.2.3.0/24
host1$ weave launch-dns 10.2.4.1/24
host1$ weave launch-proxy --with-ipam --with-dns
host1$ export DOCKER_HOST=tcp://localhost:12375

host2$ weave launch -iprange 10.2.3.0/24 host1
host2$ weave launch-dns 10.2.4.2/24
host2$ weave launch-proxy --with-ipam --with-dns
host2$ export DOCKER_HOST=tcp://localhost:12375

NB: Note that the two weaveDNS instances must be given unique IPs, on a subnet different from that used for IP allocation.

Now let us start a couple of containers, and ping one from the other, by name.

host1$ docker run -h pingme.weave.local -dti ubuntu

host2$ docker run -h pinger.weave.local  -ti ubuntu
root@pinger:/# ping pingme
PING pingme.weave.local (10.2.3.1) 56(84) bytes of data.
64 bytes from pingme.weave.local (10.2.3.1): icmp_seq=1 ttl=64 time=0.047 ms
...

Securing the docker communication with TLS

If you are connecting to the docker daemon with TLS, you will probably want to do the same when connecting to the proxy. That is accomplished by launching the proxy with the same TLS-related command-line flags as supplied to the docker daemon. For example, if you have generated your certificates and keys into the docker host's /tls directory, we can launch the proxy with:

host1$ weave launch-proxy --tlsverify --tlscacert=/tls/ca.pem \
         --tlscert=/tls/server-cert.pem --tlskey=/tls/server-key.pem

The paths to your certificates and key must be provided as absolute paths which exist on the docker host.

Because the proxy connects to the docker daemon at unix:///var/run/docker.sock, you must ensure that the daemon is listening there. To do this, you need to pass the -H unix:///var/run/docker.sock option when starting the docker daemon, in addition to the -H options for configuring the TCP listener. See the Docker documentation for an example.

With the proxy running over TLS, we can configure our regular docker client to use TLS on a per-invocation basis with

$ docker --tlsverify --tlscacert=ca.pem --tlscert=cert.pem \
     --tlskey=key.pem -H=tcp://host1:12375 version
...

or, by default, with

$ mkdir -pv ~/.docker
$ cp -v {ca,cert,key}.pem ~/.docker
$ export DOCKER_HOST=tcp://host1:12375 DOCKER_TLS_VERIFY=1
$ docker version
...

which is exactly the same configuration as when connecting to the docker daemon directly, except that the specified port is the weave proxy port.

Troubleshooting

The command

weave status

reports on the current status of various weave components, including the proxy, if it is running:

...
weave proxy is running

Information on the operation of the proxy can be obtained from the weaveproxy container logs with

docker logs weaveproxy