coreos-vulcand-example

Vulcand version: v0.8.0-beta.2

TEST ENVIRONMENT

This example is based on the coreos/example https://coreos.com/blog/zero-downtime-frontend-deploys-vulcand/ running on a 3 node coreos-cluster deployed via Vagrant.

Example Vagrantfile, user-data and config.rb can be found here: https://github.com/muemich/coreos-vagrant-vulcand

Set up

Add 172.17.8.101 example.com to /etc/hosts on your host machine,

Launch CoreOS VMs and log in,

$ vagrant up
$ vagrant ssh core-01 -- -A

Ensure etcd and vulcand is running

core@core-01 ~ $ systemctl status etcd2
● etcd2.service - etcd2
   Loaded: loaded (/usr/lib64/systemd/system/etcd2.service; disabled; vendor preset: disabled)
  Drop-In: /run/systemd/system/etcd2.service.d
           └─20-cloudinit.conf
   Active: active (running) since Tue 2015-09-22 15:00:57 UTC; 54min ago
 Main PID: 967 (etcd2)
   Memory: 38.2M
      CPU: 34.202s
   CGroup: /system.slice/etcd2.service
           └─967 /usr/bin/etcd2

Sep 22 15:01:43 core-01 etcd2[967]: 2015/09/22 15:01:43 raft: aeb20866b279648e received vote from aeb20866b279648e at term 2
Sep 22 15:01:43 core-01 etcd2[967]: 2015/09/22 15:01:43 raft: aeb20866b279648e [logterm: 1, index: 3] sent vote request to 56da6d1265bdc9ed at term 2
Sep 22 15:01:43 core-01 etcd2[967]: 2015/09/22 15:01:43 raft: aeb20866b279648e [logterm: 1, index: 3] sent vote request to eefc97cb642769af at term 2
Sep 22 15:01:43 core-01 etcd2[967]: 2015/09/22 15:01:43 raft: aeb20866b279648e received vote from 56da6d1265bdc9ed at term 2
Sep 22 15:01:43 core-01 etcd2[967]: 2015/09/22 15:01:43 raft: aeb20866b279648e [q:2] has received 2 votes and 0 vote rejections
Sep 22 15:01:43 core-01 etcd2[967]: 2015/09/22 15:01:43 raft: aeb20866b279648e became leader at term 2
Sep 22 15:01:43 core-01 etcd2[967]: 2015/09/22 15:01:43 raft: raft.node: aeb20866b279648e elected leader aeb20866b279648e at term 2
Sep 22 15:01:43 core-01 etcd2[967]: 2015/09/22 15:01:43 etcdserver: setting up the initial cluster version to 2.1.0
Sep 22 15:01:43 core-01 etcd2[967]: 2015/09/22 15:01:43 etcdserver: published {Name:d7251d6864f0497294358cf18f811017 ClientURLs:[http://172.17.8.101:2379]} to cluster eba7d2dbe11be795
Sep 22 15:01:43 core-01 etcd2[967]: 2015/09/22 15:01:43 etcdserver: set the initial cluster version to 2.1.0

systemctl status vulcand
● vulcand.service - Vulcand
   Loaded: loaded (/etc/systemd/system/vulcand.service; enabled; vendor preset: disabled)
   Active: active (running) since Tue 2015-09-22 15:02:49 UTC; 53min ago
  Process: 1070 ExecStartPre=/usr/bin/docker pull mailgun/vulcand:v0.8.0-beta.3 (code=exited, status=0/SUCCESS)
  Process: 1063 ExecStartPre=/usr/bin/docker rm vulcand (code=exited, status=1/FAILURE)
  Process: 979 ExecStartPre=/usr/bin/docker kill vulcand (code=exited, status=1/FAILURE)
 Main PID: 1331 (docker)
   Memory: 12.5M
      CPU: 123ms
   CGroup: /system.slice/vulcand.service
           └─1331 /usr/bin/docker run --name vulcand -p 80:80 -p 443:443 -p 8182:8182 -p 8181:8181 mailgun/vulcand:v0.8.0-beta.2 /go/bin/vulcand -apiInterface=0.0.0.0 -interface=0.0.0.0 -etcd=http://...

Sep 22 15:03:00 core-01 docker[1331]: 5c5ef0bea32a: Download complete
Sep 22 15:03:00 core-01 docker[1331]: 6c24554e26e5: Pulling metadata
Sep 22 15:03:01 core-01 docker[1331]: 6c24554e26e5: Pulling fs layer
Sep 22 15:03:02 core-01 docker[1331]: 6c24554e26e5: Download complete
Sep 22 15:03:02 core-01 docker[1331]: e7e8f43c66ae: Pulling metadata
Sep 22 15:03:03 core-01 docker[1331]: e7e8f43c66ae: Pulling fs layer
Sep 22 15:03:05 core-01 docker[1331]: e7e8f43c66ae: Download complete
Sep 22 15:03:05 core-01 docker[1331]: e7e8f43c66ae: Download complete
Sep 22 15:03:05 core-01 docker[1331]: Status: Downloaded newer image for mailgun/vulcand:v0.8.0-beta.2
Sep 22 15:03:05 core-01 docker[1331]: Sep 22 15:03:05.587: WARN PID:1 [supervisor.go:349] No frontends found

As there are no frontends deployed yet, the warning can be ignored.

Deploy v1 containers

Run web application v1 containers,

$ docker run -d --name example-v1.1 -p 8086:80 coreos/example:1.0.0
$ docker run -d --name example-v1.2 -p 8087:80 coreos/example:1.0.0

Configure Vulcand to proxy to v1 container,

# Register v1 containers
$ etcdctl set /vulcand/backends/v1/backend '{"Type": "http"}'
$ etcdctl set /vulcand/backends/v1/servers/v1.1 '{"URL": "http://172.17.8.101:8086"}'
$ etcdctl set /vulcand/backends/v1/servers/v1.2 '{"URL": "http://172.17.8.101:8087"}'

# To proxy to v1 containers
$ etcdctl set /vulcand/frontends/example/frontend '{"Type": "http", "BackendId": "v1", "Route": "Host(`example.com`) && Path(`/`)"}'

Then access to example.com and you can see the current version 1.0.0 .

Deploy v2 containers

OK, let's deploy the new version v2.

Run web application v2 containers,

$ docker run -d --name example-v2.1 -p 8088:80 coreos/example:2.0.0
$ docker run -d --name example-v2.2 -p 8089:80 coreos/example:2.0.0

Configure Vulcand to proxy to v2 container,

# Register v2 containers
$ etcdctl set /vulcand/backends/v2/backend '{"Type": "http"}'
$ etcdctl set /vulcand/backends/v2/servers/v2.1 '{"URL": "http://172.17.8.101:8088"}'
$ etcdctl set /vulcand/backends/v2/servers/v2.2 '{"URL": "http://172.17.8.101:8089"}'

# To proxy to v2 containers
$ etcdctl set /vulcand/frontends/example/frontend '{"Type": "http", "BackendId": "v2", "Route": "Host(`example.com`) && Path(`/`)"}'

Then access to example.com and you can see the current version 2.0.0 .

Hints

If you're sitting behind a proxy you have to run an own discovery enpoint behind the proxy or if possible try to bypass the proxy. On a local machine mobile tethering will do the trick.

pros and cons of using vulcand

Pros:

• Interacts directly with etcd
• Changes don't need a restart
• No config files needed

Cons:

• Still beta
• No heavy development visible

When to use

In test environment with moderate load.

Future work

Dynamic frontend and backend deployments