Containers launched via the proxy use weaveDNS automatically if it is running when they are started - see the weaveDNS usage section for an in depth explanation of the behaviour and how to control it.
Typically, the proxy passes on container names as-is to weaveDNS for registration. However, there are situations in which the final container name may be out of your control (for example, if you are using Docker orchestrators which append control/namespacing identifiers to the original container names).
For those situations, the proxy provides the following flags:
When launching a container, the hostname is initialized to the
value of the container label using key
<labelkey>. If no
provided, then the container name is used.
Additionally, the hostname is matched against a regular expression
<regexp> and based on that match,
<replacement> is used to obtain the final hostname, and then handed over to weaveDNS for registration.
For example, you can launch the proxy using all three flags, as follows:
host1$ weave launch --hostname-from-label hostname-label --hostname-match '^aws-[0-9]+-(.*)$' --hostname-replacement 'my-app-$1' host1$ eval $(weave env)
Note: regexp substitution groups must be pre-pended with a dollar sign (for example,
$1). For further details on the regular expression syntax see Google’s re2 documentation.
After launching the Weave Net proxy with these flags, running a container named
aws-12798186823-foo without labels results in weaveDNS registering the hostname
my-app-foo and not
host1$ docker run -ti --name=aws-12798186823-foo weaveworks/ubuntu ping my-app-foo PING my-app-foo.weave.local (10.32.0.2) 56(84) bytes of data. 64 bytes from my-app-foo.weave.local (10.32.0.2): icmp_seq=1 ttl=64 time=0.027 ms 64 bytes from my-app-foo.weave.local (10.32.0.2): icmp_seq=2 ttl=64 time=0.067 ms
Also, running a container named
foo with the label
hostname-label=aws-12798186823-foo leads to the same hostname registration.
host1$ docker run -ti --name=foo --label=hostname-label=aws-12798186823-foo weaveworks/ubuntu ping my-app-foo PING my-app-foo.weave.local (10.32.0.2) 56(84) bytes of data. 64 bytes from my-app-foo.weave.local (10.32.0.2): icmp_seq=1 ttl=64 time=0.031 ms 64 bytes from my-app-foo.weave.local (10.32.0.2): icmp_seq=2 ttl=64 time=0.042 ms
This is because, as explained above, if providing
to the proxy, the specified label takes precedence over the container’s name.