Talk given at config management camp 2020 about mgmtconfig.

1. CfgMgmtCamp Ghent
Julien Pivotto
@roidelapluie
Why you should revisit
mgmt
February 04 2020

2. CfgMgmtCamp Ghent
Julien Pivotto
@roidelapluie
alt title:
mgmt without reworks
February 04 2020

3. simpli ed de nition
Bring the system to a certain state.
Change the state of a system.
Con guration Management
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4. • You know the desired state.
• You know what you want to do.
How to achieve it
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5. • You know the desired state: Puppet / Terraform.
• You know what you want to do: Chef / Ansible / Pulumi.
Tooling
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6. Changing the desired state is still hard in some cases.
Takes time and refactoring.
but ...
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7. Some changes are not desired. Or not anticipated.
And you don't know the desire state.
changes
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8. ?
Tooling
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9. mgmt
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10. but what is mgmt?
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11. generalities...
• Open Source (GPLv3)
• Initial commit in 2015
• Con g Management Tool
• Golang
mgmt
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12. • Events
• Graphes
• Vertex
• Language
• DSL
• Resources
You name it, you have it.
Buzzwords
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13. Event-Based
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14. Changes in the infrastructure or in the applications
• Adding a new server
• Removing a le
Events
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15. Changes outside of the infrastructure
• External connectivity is not working
• Package updates are available
• More tra c on the platform
Events
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16. • Add a new server: register in DNS, Quorum, Frontend
• Time: Enable / Disable services
• Updates: roll the updates, ensure your con g is still there
What would you do
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17. import "prometheus"
import "datetime"
$now = datetime.now()
$v = prometheus.instant_query_value(
"sum(rate(http_requests[5m]))", $now
)
if $v > 300 {
cron "batch_job" {
ensure => "absent",
}
}
Reaction on events
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18. Desired state
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19. • mgmt runs as a daemon
• The desire state is "compiled"
• Takes the current state as input
• Recalculated on events
What do you know in advance?
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20. Computing a desire state based on facts and events
vs
Writing a new desire state on each change
vs
Running commands to x the state and nishing in an
unknown state
Evolution
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21. Batteries included
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22. PCS
@roidelapluie © 2011 Puppet Labs

23. • package
• le
• service
pkg "cowsay" {
state => "installed",
}
Resources
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24. • net interface
• mountpoint
• timer
mount "/mnt/foo" {
state => "exists",
device => "/dev/sdb1",
type => "ext4",
}
Resources
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25. • exec
• users
• group
Resources
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26. • augeas
• consul:kv
Resources
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27. • container
• vm
• ec2
aws:ec2 "ec2example" {
state => running,
region => "ca-central-1",
type => "t2.micro",
imageid => "ami-5ac17f3e",
}
Resources
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28. • time
• le
• cpucount
• uptime
External events
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29. In addition to that, each resource has its own events.
And will ensure its own state.
Resources events
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30. Improving our work
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31. Traditional dependency management:
• Explicitly de ned dependencies: takes time before
applying the state
• Ordered tasks: takes time while applying the state
Machines should help humans
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32. • A package contains les
• A cron job uses a command
Machine knows..
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33. $ rpm -ql bash
/etc/skel/.bash_logout
/etc/skel/.bash_profile
/etc/skel/.bashrc
/usr/bin/alias
/usr/bin/bash
/usr/bin/bashbug
/usr/bin/bashbug-64
/usr/bin/bg
/usr/bin/cd
/usr/bin/command
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34. If a cron job requires a command that will be installed
by a package, install
the package rst.
Why should I tell the machine?
Auto-Edges
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35. If I need to install 10 packages, install them in one go.
Why should I tell the machine?
dnf install python3 httpd mysqld
Auto-Grouping
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36. The language
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37. How would you implement events in an existing
language?
Hard to reuse a programming language as we can't
support all its features. and
don't want to.
mgmt is close to a "functional" language.
mgmt language
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38. cron "purpleidea-oneshot" {
session => true,
trigger => "OnCalendar",
time => "*:*:0",
}
svc "purpleidea-oneshot" {
state => "stopped",
}
mgmtlang example
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39. import "fmt"
import "example"
print "answer" {
msg => fmt.printf(
"the answer to life, the universe, and everyt
example.answer()),
}
mgmtlang example
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40. Monitoring
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41. • What is the state of my infra?
• How much do I need to adapt its state?
• What are the changes?
Prometheus enabled
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42. Why this talk?
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43. • You have probably seen only parts of it
• You only remember the reworks
• Presented early ; much has changed now.
You probably don't know mgmt
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44. • Quick and e cient
• Does a lot of work for us
• Maintains a desired state over (real) time
mgmt solves problems elegantly
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45. https://github.com/purpleidea/mgmt
Discover it!
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46. Julien Pivotto
@roidelapluie
roidelapluie@inuits.eu
Essensteenweg 31
2930 Brasschaat
Belgium
Contact:
info@inuits.eu
+32-3-8082105