User talk:Jch/consul

This material is work-in-progress ... Do not follow instructions here until this notice is removed. (Last edited by Jch on 20 Apr 2015.)

Consul

Introduction

This page is currently my experimental log about consul on AL.

Downloaded package: consul-0.5.0-r0.apk from http://repos.mauras.ch/alpinelinux/x86_64/

Will prepare 5 KVM: 3 consul server (in run-from-ram mode) and 2 consul agent (a SAN (NBD) and a LXC host in data mode) on an isolated network.

We will experiment to find the right spec to allocate the consul servers for 100 to 1000 agents.

We plan to orchestrate our VM fleet based on consul events, envconsul and consul-template. All with ash scripts and smart setup.

We combine our PXE servers and the consul ones to inherit from the consul resilence (consul leader) to offer high-availability (HA) (but still in ram only) to the PXE service.

Currently, we have scripts to adapt a freshly PXE booted machine into a

• PXE and consul server
• SAN (san.service.consul)
• generic diskless machine (for KVM or services) (kvm.service.consul)
• generic data mode machine (/var) (for LXC or services) (lxc.service.consul)
• machine with physical drives (raid + KVM + SAN) (raid.service.consul; kvm.service.consul)
• specific sys mode machine (sys.service.consul)

We have defined:

• *.kvm.service.consul
• *.lxc.service.consul
• *.san.service.consul
• *.nbd.service.consul
• *.raid.service.consul
• *.nas.service.consul
• *.sys.service.consul
• time.service.consul
• repo.service.consul
• resolver.service.consul
• dns.service.consul
• collectd.service.consul
• webcache.service.consul
• mariadb.service.consul
• *.ldap.service.consul
• relay.service.consul
• syslog.service.consul
• *.ceph.service.consul
• *.git.service.consul
• *.vpn.service.consul
• etc

Install

We will just focus on the consul installation and configuration parts.

wget http://repos.mauras.ch/alpinelinux/x86_64/consul-0.5.0-r0.apk
apk add consul-0.5.0-r0.apk --allow-untrusted --force

Configuration

Consul v0.5.0
Consul Protocol: 2 (Understands back to: 1)

By default, there are 4 files in /etc/consul

acl.json.sample      encrypt.json.sample  server.json          tls.json.sample

Consul Server

As in our setup we want as many PXE server (in stand-by mode) than consul server, installing a consul server is done by a script doing

1. whoami on the LAN ?
2. find IP of boot server (is consul leader)
3. preconfigure OS
4. install package from stable
5. install package from edge
6. rsync data
7. install experimental consul package
8. start consul as server
9. untie from boot server
10. get ENV from consul
11. configure networking
12. start networking
13. start sshd
14. (restart consul?)
15. configure dnsmasq
16. start dnsmasq
17. configure ntpd
18. start ntpd
19. register time.service.consul
20. configure collectd
21. start collectd
22. configure dhcpd
23. configure pxelinux
24. start in.tftp
25. configure NFS
26. start NFS
27. configure darkhttpd
28. start darkhttpd
29. register repo.service.consul
30. register pxe.service.consul

dhcpd will be started manually for now but later by the consul leader election.

DNSmasq with consul

apk add dnsmasq
mkdir -p /etc/dnsmasq.d
echo "server=/consul/127.0.0.1#8600" > /etc/dnsmasq.d/10-consul
echo "resolv-file=/etc/resolv.dnsmasq" > /etc/dnsmasq.d/20-resolv
echo "nameserver ${DNS1}" > /etc/resolv.dnsmasq
echo "nameserver ${DNS2}" >> /etc/resolv.dnsmasq
echo <<EOF > /etc/conf.d/dnsmasq
MASQ_OPTS="--user=dnsmasq --group=dnsmasq --interface=eth0 --conf-dir=/etc/dnsmasq.d"
EOF
rc-service dnsmasq start

Consul Agent

We need to lauch the consul service after being able to read the IP address of the PXEserver involved.
This particuliar address will be used to join the consul cluster as agent.

1. whoami on the LAN ?
2. find IP of boot server (is consul leader)
3. preconfigure OS
4. install package from stable
5. install package from edge
6. install experimental consul package
7. get standard agent config
8. start consul as agent
9. join consul cluster
10. untie from boot server
11. get ENV from consul
12. configure dnsmasq
13. restart dnsmasq
14. configure collectd
15. start collectd

Whenever possible, a service will be referenced by its name (like collectd.service.consul for the collectd server).
Consul agent and dnsmasq are the 2 first services to be started on each machine.

Bootstrap the consul cluster

Is to launch the 3 first servers lying to them about the first consul server because we do not want to switch PXE production at the same time we are introducing consul...

We have scipts to adapt a freshly PXE launched machine to the role of:

• PXE and consul server
• SAN
• generic diskless machine (for KVM or services)
• generic data mode machine (/var) (for LXC or services)
• machine with physical drives (raid + KVM + SAN)
• specific sys mode machine (apkovl ou -boot c)

Usage

HTTP API seems unavailable with the default configuration provided by the package...

How to list services or to interact with the k/v store?

Machines discovery

List machines =

consul members

or

curl localhost:8500/v1/catalog/nodes

list PXEservers = servers in "consul members"

get consul leader = ???

Services discoevry

Register service =

echo '{"service": {"name": "pxe"}}' > /etc/consul/pxe.json ; consul reload

List services :

curl http://localhost:8500/v1/agent/services : Returns the services the local agent is managing 
curl http://localhost:8500/v1/catalog/services : Lists services in a given DC 
curl http://localhost:8500/v1/catalog/service/<service> : Lists the nodes in a given service
curl http://localhost:8500/v1/catalog/node/<node> : Lists the services provided by a node

Key/Value storage

k/v