How to change the cloud-config to specify a specific version of etcd - coreos

Question

I am using core-os and configuring it with cloud-config files. I need to use a etcd-service for my application.
This is the relevant part of the cloud-config file.
- name: etcd.service
command: start
content: |
[Unit]
Description=etcd
Requires=setup-network-environment.service
After=setup-network-environment.service
[Service]
EnvironmentFile=/etc/network-environment
User=etcd
PermissionsStartOnly=true
ExecStart=/usr/bin/etcd \
--name ${DEFAULT_IPV4} \
--addr ${DEFAULT_IPV4}:4001 \
--bind-addr 0.0.0.0 \
--discovery https://discovery.etcd.io/SOMEKEY \
--data-dir /var/lib/etcd \
--http-read-timeout 86400 \
--peer-addr ${DEFAULT_IPV4}:7001 \
--snapshot true
Restart=always
RestartSec=10s
I am not sure how to update the version of etcd.

Answer 1

Turns out etcd2 is already installed on coreos. It is currently shipped in the coreos-alpha 653 release, alongside etcd.
To change it in the cloud-config, you just have to change
ExecStart=/usr/bin/etcd
to
ExecStart=/usr/bin/etcd2
and remove some flags which are deprecated in etcd2.

Answer 2

I have a template generator and I can tell it to switch between etcd and etcd2 by setting a single environment variable. One thing I did was use the etcd2.service name or etcd.service (I didn't just put the etcd2 configuration in the etcd unit section). That could work, but, you might think about changing all etcd.service references in your file to etcd2.service. Anyway, here is the ExecStart section for etcd2:
ExecStart=/usr/bin/etcd2 \
--name ${d['etcd']['name']} \
--advertise-client-urls ${d['etcd']['advertise-client-urls']} \
--discovery ${d['etcd']['discovery']} \
--data-dir /var/lib/etcd \
--initial-advertise-peer-urls ${d['etcd']['initial-advertise-peer-urls']} \
--listen-client-urls ${d['etcd']['listen-client-urls']} \
--listen-peer-urls ${d['etcd']['listen-peer-urls']}
Here are my env variables for d['etcd']:
"etcd": {
"mver":"etcd2.service",
"discovery":"http://discovery.etcd.io/SOMEKEY",
"addr":"$private_ipv4:4001",
"name":"$private_ipv4",
"peer-addr":"$private_ipv4:7001",
"advertise-client-urls":"http://$private_ipv4:2379",
"initial-advertise-peer-urls":"http://$private_ipv4:2380",
"listen-client-urls":"http://0.0.0.0:2379,http://0.0.0.0:4001",
"listen-peer-urls":"http://$private_ipv4:2380,http://$private_ipv4:7001"
}
Somewhere I remember reading that $public_ipv4 was needed for one of these variables, put, I just went with the private ip for all of them. My environment here is digital ocean. Be sure to use coreos-alpha (at least I think that is still required at the time of this writing).

Answer 3

The cloud-config parser has built in support for etcd2 and the new configuration parameters: https://coreos.com/docs/cluster-management/setup/cloudinit-cloud-config/#etcd2
An example:
#cloud-config
coreos:
etcd2:
# generate a new token for each unique cluster from https://discovery.etcd.io/new?size=3
discovery: https://discovery.etcd.io/<token>
# multi-region and multi-cloud deployments need to use $public_ipv4
advertise-client-urls: http://$public_ipv4:2379
initial-advertise-peer-urls: http://$private_ipv4:2380
# listen on both the official ports and the legacy ports
# legacy ports can be omitted if your application doesn't depend on them
listen-client-urls: http://0.0.0.0:2379,http://0.0.0.0:4001
listen-peer-urls: http://$private_ipv4:2380,http://$private_ipv4:7001