HA (High availability) and clustering might be a quite unknown feature inside openSUSE (Pacemaker, Corosync, crmsh, resource agents, etc), but it provides really interesting and powerful options.
In order to explain how HA cluster works in a more visible and funnier way, I will expose a didactic demonstration with a cluster created with some Raspberries and Webcams. The main idea is to create a high available video security system with the tools provided in openSUSE (and some custom code, of course). In this use case, the cluster will host a Webcam service where if the current Webcam (or raspberry with the connected Webcam) fails the whole system is migrated to the seconde node, and the service continues working in the same address and without downtime. This will help to understand what is application or service level redundancy and some of the advantages of it.
3. ● From the Basque Country (Spain) but living in the Canary Islands.
● Studied computer science in the University of Basque Country (UPV).
● Working at Suse since last October in the
SLES4SAP and HA team as software engineer
(with Python, Salt and Terraform mainly).
● Hobbies: Surf, time in nature, friki things
(anime, videogames, etc) .
5. Christmas dinner 2018...
My brother and I got a new job. Now he works in a
company that builds elevators. So as always:
My parents:
“Oh!! I see. And how fast they move?
How many people can use them?
Which material do you use?”
6. So they talk about that until...
Dad: “Xabi, sorry, we could talk about what you do,
but,
you know...”
Me: “You don’t know what I do, right?
Mmm... you work with a computer, don’t you?
7. So I decided to do
something to make
them understand
what I do!
11. Let’s do a High Available webcams service! I can
use Motion for that.
Motion: https://motion-project.github.io/
So I decided to do something
simpler…
13. “Oh man, and now I have to configure all the
raspberry pi-s…
And redo everything every time I fail… So
annoying”
“Dude! But you are working with Salt all the time!
Create some states to configure everything!
But...
14. And finally the project was born!
https://github.com/arbulu89/ha-webcams-raspberry
19. But let’s show the project using a
demo
What can go wrong?
20. Let’s leverage Salt for everything!
● Configure the Salt Master using Salt
● Configure the nodes Salt Minion using salt (WTF!!)
– salt-ssh
● Configure HA and Motion using Salt
21. Configure Salt Master
1. Install Salt Master
2. Auto accept Salt Minions connection
3. Install HA salt formula
https://github.com/arbulu89/ha-webcams-
raspberry/tree/master/salt/setup
22. But… What is a salt formula?
Basically, a bunch of states
to configure certain
components (HA for
example).
IDEMPOTENCY ASSURED!
24. Configure the nodes with salt-ssh
We can use salt-ssh to run salt states in nodes
without salt-minion. Isn’t it great?!!!
We need to define a roster for that:
25. And finally configure Motion and HA
Now we have everything ready, we only need run
Motion and HA cluster states. Easy!
High Available Cluster!!
27. HA cluster will assure that there is
not downtime!
● What if the Motion daemon stops working?
– I will restart the daemon!
● What if the node crashes?
– I will migrate Motion daemon to the 2n node
● But the IP address to monitor the service will be
different!
– I will create a virtual address and migrate with Motion
28. How are going to do that?
Simple! HA cluster monitors resources (instead of
machines).
We can monitor a systemd daemon for example.
29. Disclaimer!!!
So, you will be thinking: “Hey! Why are you not just
using the 2 webcams together?!!”
Remember! This is just a demonstration to
show how to use Salt and HA in a more visual
way.
34. License
This slide deck is licensed under the Creative Commons Attribution-ShareAlike 4.0
International license.
It can be shared and adapted for any purpose (even commercially) as long as Attribution
is given and any derivative work is distributed under the same license.
Details can be found at https://creativecommons.org/licenses/by-sa/4.0/
General Disclaimer
This document is not to be construed as a promise by any participating organisation to
develop, deliver, or market a product. It is not a commitment to deliver any material,
code, or functionality, and should not be relied upon in making purchasing decisions.
openSUSE makes no representations or warranties with respect to the contents of this
document, and specifically disclaims any express or implied warranties of merchantability
or fitness for any particular purpose. The development, release, and timing of features or
functionality described for openSUSE products remains at the sole discretion of
openSUSE. Further, openSUSE reserves the right to revise this document and to make
changes to its content, at any time, without obligation to notify any person or entity of
such revisions or changes. All openSUSE marks referenced in this presentation are
trademarks or registered trademarks of SUSE LLC, in the United States and other
countries. All third-party trademarks are the property of their respective owners.
Credits
Template
Richard Brown
rbrown@opensuse.org
Design & Inspiration
openSUSE Design Team
http://opensuse.github.io/branding-
guidelines/
