visibilityspots/keepalived
A docker image to run Keepalived
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visibilityspots/keepalived repository overview
Keepalived
a docker container which runs keepalived.org
orginally based on the work of linkvt but simplified the approach for my own needs along the way.
run
This image require the kernel module ip_vs loaded on the host;
# modprobe ip_vs
and needs to be run with the NET_ADMIN linux capability using the host network mode;
$ docker run --cap-add=NET_ADMIN --cap-add=NET_BROADCAST --cap-add=NET_RAW --net=host --name keepalived --rm visibilityspots/keepalived:latest
Configuration
Environment variables defaults are set in the Dockerfile and can be overriden;
ENV KEEPALIVED_INTERFACE eth0
ENV KEEPALIVED_STATE BACKUP
ENV KEEPALIVED_ROUTER_ID 21
ENV KEEPALIVED_PRIORITY 150
ENV KEEPALIVED_ADVERT_INT 1
ENV KEEPALIVED_VERSION 2
ENV KEEPALIVED_UNICAST_PEERS 192.168.0.11 - 192.168.0.12
ENV KEEPALIVED_VIRTUAL_IPS 192.168.0.10
ENV KEEPALIVED_VIRTUAL_ROUTES 192.168.0.0/24 dev eth0 scope link src 192.168.0.10
ENV KEEPALIVED_PASSWORD d0ck3r
ENV KEEPALIVED_NOTIFY notify "/usr/local/bin/keepalived-notify.sh"
ENV KEEPALIVED_CHECK_COMMAND
ENV KEEPALIVED_CHECK_INTERVAL 2
ENV KEEPALIVED_CHECK_TIMEOUT 2
ENV KEEPALIVED_CHECK_FALL 2
ENV KEEPALIVED_CHECK_RISE 2
ENV KEEPALIVED_USE_VMAC false
ENV KEEPALIVED_CONF /etc/keepalived/keepalived.conf
Health check
By default the virtual ip only follows the host: it moves when keepalived stops
answering, not when the service behind the address is broken. Setting
KEEPALIVED_CHECK_COMMAND renders a vrrp_script and a track_script that run
the command every KEEPALIVED_CHECK_INTERVAL seconds;
$ docker run --cap-add=NET_ADMIN --cap-add=NET_BROADCAST --cap-add=NET_RAW --net=host --env KEEPALIVED_CHECK_COMMAND="wget -q -O /dev/null http://127.0.0.1:8082/ping" --name keepalived --rm visibilityspots/keepalived:latest
The script runs with weight 0: after KEEPALIVED_CHECK_FALL failures the
instance goes to FAULT and releases the virtual ip to a peer, rather than
lowering its own priority. Leaving KEEPALIVED_CHECK_COMMAND empty renders
neither block, so nothing changes for an existing configuration.
Failover timing
KEEPALIVED_ADVERT_INT is the advertisement interval in seconds and accepts
fractions. It only matters when a host disappears without warning: a backup
waits roughly three intervals before it declares the master gone. A master that
fails its health check, or that is stopped cleanly, sends a priority 0 advert
and is taken over right away no matter what this is set to.
Values below one second need KEEPALIVED_VERSION=3: VRRPv2 only accepts whole
seconds and refuses the configuration otherwise. VRRPv3 in turn has no
authentication - the protocol dropped it - so the authentication block is left
out of the configuration when version 3 is selected. On a shared segment that
trade needs to be a deliberate one.
Virtual mac
Without a virtual mac the virtual ip migrates between the real mac addresses of
the participating hosts, which mac aware equipment reports as an ip conflict
after every failover. KEEPALIVED_USE_VMAC=true gives the address its own
00:00:5e:00:01:<router_id> mac that travels with it, and adds vmac_xmit_base
so the vrrp adverts keep going out over the underlying interface - without that
the unicast adverts would be sourced from an interface that only carries the
virtual ip.
Override ENV variables
Environment variables can be set by adding the --env argument in the command line, for example:
$ docker run --cap-add=NET_ADMIN --cap-add=NET_BROADCAST --cap-add=NET_RAW --net=host --env KEEPALIVED_INTERFACE="eno1" --env KEEPALIVED_PASSWORD="password!" --env KEEPALIVED_PRIORITY="100" --name keepalived --rm visibilityspots/keepalived:latest
build
$ docker build -t visibilityspots/keepalived:latest .
buildx
$ docker run --rm --privileged multiarch/qemu-user-static --reset -p yes
$ docker buildx build -t visibilityspots/keepalived:latest --platform linux/amd64,linux/arm/v6,linux/arm/v7 --push .
dgoss
I wrote some tests in a goss.yaml file which can be executed by dgoss to test the created image
$ dgoss run visibilityspots/keepalived:2.2.8
INFO: Starting docker container
INFO: Container ID: 6e6ea44f
INFO: Sleeping for 0.2
INFO: Container health
INFO: Running Tests
File: /usr/local/bin/keepalived-notify.sh: exists: matches expectation: true
File: /etc/keepalived/keepalived.conf: exists: matches expectation: true
File: /etc/keepalived/keepalived.conf.tmpl: exists: matches expectation: true
Command: keepalived --version: exit-status: matches expectation: 0
Package: keepalived: installed: matches expectation: true
Package: keepalived: version: matches expectation: ["2.2.8-r0"]
Package: envsubst: gettext-envsubst: installed: matches expectation: true
Total Duration: 0.006s
Count: 7, Failed: 0, Skipped: 0
INFO: Deleting container
act
using act for local testing of the written github actions makes my life and commit history a lot easier;
Stage Job ID Job name Workflow name Workflow file Events
0 update update docker-hub-description docker-hub-description.yml push
0 main main CI main.yml push
0 scan scan trivy trivy.yml push,schedule
License
Distributed under the MIT license
Tag summary
Content type
Image
Digest
sha256:0567b009a…
Size
4.4 MB
Last updated
7 days ago
docker pull visibilityspots/keepalived