Matthias Radestock
dbc683f891
Weave sends all gossip down new connections. We do this so that new peers learn about all gossip'ed information quickly, thus enabling them to process subsequent incremental updates. In particular, for topology gossip it ensures that the remote peer learns about all other peers. This ensures that the incremental update, which is sent as a result of the new connection getting established and which may reference a number of other peers, can be processed. So the intent really is to send all gossip to new peers. But what we actually do is send it down every new connection. Not every new connection is from a new peer. In fact most connections aren't. Hence the current approach is wasteful. To fix this we need a conservative detection of new peers, i.e. it is preferable to have false positives. This contrasts with existing logic in the handshake code. The criteria we use is whether our peer has a unicast route to the other peer. That is only the case when there is a continuos chain of symmetric, established connections. The establishment of these connections should have triggered the sending of all gossip to the other peer. So we don't need to send it ourself. Fixes #454.
Weave - the Docker network
Weave creates a virtual network that connects Docker containers deployed across multiple hosts.
Applications use the network just as if the containers were all plugged into the same network switch, with no need to configure port mappings, links, etc. Services provided by application containers on the weave network can be made accessible to the outside world, regardless of where those containers are running. Similarly, existing internal systems can be exposed to application containers irrespective of their location.
Weave can traverse firewalls and operate in partially connected networks. Traffic can be encrypted, allowing hosts to be connected across an untrusted network.
With weave you can easily construct applications consisting of multiple containers, running anywhere.
Weave works alongside Docker's existing (single host) networking capabilities, so these can continue to be used by containers.
Installation
Ensure you are running Linux (kernel 3.5 or later) and have Docker (version 0.9.1 or later) installed. Then install weave with
sudo wget -O /usr/local/bin/weave \
https://github.com/zettio/weave/releases/download/latest_release/weave
sudo chmod a+x /usr/local/bin/weave
CoreOS users see here for an example of installing weave using cloud-config.
Quick Start Screencast
Example
Say you have docker running on two hosts, accessible to each other as
$HOST1 and $HOST2, and want to deploy an application consisting of
two containers, one on each host.
On $HOST1 run (as root)
host1# weave launch
host1# C=$(weave run 10.2.1.1/24 -t -i ubuntu)
The first line starts the weave router, in a container. This needs to
be done once on each host. The required docker image for the weave
router container is downloaded automatically. There is also a weave setup command for downloading this and other images required for
weave operation; this is a strictly optional step which is especially
useful for automated installation of weave and ensures that any
subsequent weave commands do not encounter delays due to image
downloading.
The second line runs our application container. We give it an IP
address and network, in
CIDR notation.
weave run invokes docker run -d with all the parameters following
the IP address and network. So we could be launching any container
this way; here we just take a stock ubuntu container and launch a
shell in it. There's also a weave start command, which invokes
docker start for starting existing containers.
If our application consists of more than one container on this host we simply launch them with a variation on that second line.
The IP addresses and netmasks can be anything you like, but make sure they don't conflict with any IP ranges in use on the hosts or IP addresses of external services the hosts or containers need to connect to. The same IP range must be used everywhere, and the individual IP addresses must, of course, be unique.
We repeat similar steps on $HOST2...
host2# weave launch $HOST1
host2# C=$(weave run 10.2.1.2/24 -t -i ubuntu)
The only difference, apart from the choice of IP address for the
application container, is that we tell our weave that it should peer
with the weave on $HOST1 (specified as the IP address or hostname, and
optional :port, by which $HOST2 can reach it). NB: if there is a
firewall between $HOST1 and $HOST2, you must open port 6783 for TCP
and UDP.
Note that we could instead have told the weave on $HOST1 to connect to
$HOST2, or told both about each other. Order does not matter here;
weave automatically (re)connects to peers when they become
available. Also, we can tell weave to connect to multiple peers by
supplying multiple addresses, separated by spaces. And we can
add peers dynamically.
Now that we've got everything set up, let's see whether our containers can talk to each other...
On $HOST1...
host1# docker attach $C
root@28841bd02eff:/# ping -c 1 -q 10.2.1.2
PING 10.2.1.2 (10.2.1.2): 48 data bytes
--- 10.2.1.2 ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max/stddev = 1.048/1.048/1.048/0.000 ms
Similarly, on $HOST2...
host2# docker attach $C
root@f76829496120:/# ping -c 1 -q 10.2.1.1
PING 10.2.1.1 (10.2.1.1): 48 data bytes
--- 10.2.1.1 ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max/stddev = 1.034/1.034/1.034/0.000 ms
So there we have it, two containers on separate hosts happily talking to each other.
Find out more
Contact Us
Found a bug, want to suggest a feature, or have a question?
File an issue, or email
help@weave.works. When reporting a bug, please include which version of
weave you are running, as shown by weave version.
Follow weave on Twitter: @weaveworks.
Read the Weave blog: Weaveblog.
IRC: #weavenetwork