My sensu tutorial from the nycdevops Meetup on November 14, 2013.

1. SENSE AND
SENSU-BILITY
Painless Metrics And Monitoring
In The Cloud with Sensu
Bethany Erskine
nycdevops Meetup
http://github.com/skymob/sensu-tutorial
Thursday, November 14, 13

2. DO YOU LOVE
YOUR
MONITORING
SETUP?
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3. #MONITORINGLOVE
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4. MY STORY
+
(╯︵╰,)
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5. Thursday, November 14, 13

6. Thursday, November 14, 13

7. WHY SENSU
✓Ruby
Plugins can be written in any
✓language
✓
✓community
sensu-chef cookbook
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8. WHY SENSU
✓re-use Nagios checks
metrics and checks all collected by
✓one system
✓
✓easy to scale
Graphite integration
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9. WHY SENSU
✓“Can I do X with Sensu?” probably!
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10. WHY SENSU
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11. WHY SENSU?
✓
Sensu source is well-written and
easy to parse
✓
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https://github.com/sensu

12. WHY SENSU?
✓sensu-community-plugins
80 contributors
✓
✓over 600 plugins
https://github.com/sensu/sensu✓community-plugins
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13. TODAY at
PAPERLESS
Two Sensu environments (prod/testing)
~ 250 - 275 instances of sensu-client
4-6 Sensu-server instances
25k Metrics/Hour to Graphite
1 custom dashboard
1 custom CLI
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14. RESOURCES
All of our
✓virtualized.Sensu infrastructure is
We typically give a
✓box 1.5GB RAM and sensu-server
4 processors,
scaling up RAM for any box running
more than one Sensu service on it.
4GB
✓install RAM for a monolithic Sensu
(Rabbit, Redis, all Sensu
components on one)
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15. AS WE GREW
Growing pains and lessons learned...
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16. NEEDS MORE
SENSU
✓High load on Sensu server
Backed-up queues in RabbitMQ
✓
TIP: set up check to monitor the
✓RabbitMQ ready queue size, you'll
want an email when the queue
grows about 10K and stays there
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17. HOW TO SCALE
✓Add more sensu-server instances
No special configuration needed
✓
checks will be
✓robin fashion todistributed in roundthe sensu-servers
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18. GRAPHITE PAINS
symptoms: backed up queues in
✓RabbitMQ, spotty graphs
cluster couldn’t
with the
✓large amount of keep upwe were
metrics
now serving it via AMQP
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19. GRAPHITE PAINS
✓
Solution: stop collecting metrics
every 10 seconds (excessive!)
✓
moved staging metrics to staging
Graphite cluster
✓
Moved prod Graphite cluster to
SSD
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20. THE MIGRATION
or, How To Quit Nagios in Ten Easy Steps
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21. STEP 1: NUKE AND
PAVE
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22. STEP 2: PLAN
METRICS AND MONITORING SURVEY
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23. METRICS AND MONITORING SURVEY
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24. STEP 3: DEFINE
GLOBALS
✓CHECKS: must be actionable!
✓METRICS: go nuts
HANDLERS: EMAIL for everything
✓initially, added Pagerduty later.
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25. OUR GLOBALS
✓
CHECKS: disk usage, swap usage,
zombie processes, RO filesystems
✓
METRICS: vmstat, disk usage, cpu,
memory, interface and disk perf
✓
HANDLERS: Email, Campfire,
Pagerduty
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26. STEP 4: DEFINE
SPECIFICS
✓
For each server role, define
additional states to be checked and
alerted on:
✓Process Checks
✓System Checks
✓Service Checks
✓Service Metrics
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27. STEP 5: SET UP A
PLACE TO TEST
✓
Set up a permanent testing Sensu
stack using your CM tool of choice
✓
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we used sensu-chef cookbook

28. STEP 6: SET A
WORKFLOW
✓
Develop and document a workflow
for implementing, testing,
deploying and signing off on
checks
✓
You’ll get the best coverage if
anyone (developers or ops) can
easily add checks and metrics to
Sensu
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29. EXAMPLE
WORKFLOW
add new sensu_check
✓appropriate cookbook definitions to the
in Chef
deploy
✓Chef new check to staging env using
✓Pull Request with sample graphs or alerts
✓Code Review from colleague
✓Deploy to Prod
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30. SENSU IN CHEF
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31. STEP 7: EXECUTE
WORKFLOW
Starting with the low-hanging
✓(plugins that already existed infruit
sensu-community-plugins
repository), configure and deploy
each check in the worksheet to the
testing Sensu server
deploy sensu-client to a few select
✓machines
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32. STEP 8: WATCH
THE WATCHER
Set up some bare-minimum 3rd
✓party monitoring for the Sensu
servers
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33. Thursday, November 14, 13

34. MONITOR THE
MONITOR
✓
Other ideas: have Testing Sensu
monitor Prod Sensu
✓
Sensu can collect metrics about
itself
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35. STEP 9: ROLLOUT
Deploy your
✓infrastructureProduction server
Roll out the client
✓the rest of the yourand checks to
prod
environments.
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36. STEP 10: TUNE
✓
Expect to need to tune
✓and alert occurrences. thresholds
Laissez le bon alertes roulent!
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37. SENSU
ARCHITECTURE
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38. SENSU
ARCHITECTURE
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39. OMNIBUS
INSTALLER
is awesome
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40. LET’S PLAY WITH
SENSU
If you haven’t been able to get your
sandboxes up and running,
please pair with someone near you.
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41. SANDBOX GOALS
✓
Get familiar with Sensu
configuration
✓
✓Deploy a check
Trigger an alert on that check
✓
Give you something to take home
✓and hack on
Install a Handler
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42. OOPS
If you mess anything up:
vagrant halt; vagrant up
Worst case:
vagrant destroy; vagrant up
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43. TWO
VIRTUALBOXES
Sensu-Server and Sensu-Client
Vagrant/Chef
Centos 6.4
Sensu Version 0.10.2
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44. SENSU
CONFIGURATION
Please open up a terminal
✓into both your sensu-serverand SSH
and
sensu-client VMs
✓sudo su ✓cd /etc/sensu
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45. SENSU
CONFIGURATION
✓/etc/sensu/config.json - config for
redis, rabbitmq, api and dashboard
✓/etc/sensu/conf.d/ - checks go here
✓/etc/sensu/conf.d/client.json client configuration, subscriptions
✓
/etc/sensu/{extensions|handlers|
mutators|plugins}
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46. TRIGGER AN
ALERT!
On sensu-client:
service sensu-client stop
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47. CHECK YOUR
DASHBOARD
Open a web browser and
✓http://10.254.254.10:8080 go to
username:
✓secret admin / password:
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48. HANDLERS
✓
A HANDLER takes action on an
event using a pipe, TCP, UDP,
AMQP, or a set of other handlers
Examples: send an
send
✓event to Pagerduty,email,metrics to
send
Graphite
✓
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Default is “debug”

49. HANDLER
EXAMPLES
✓BASIC: send an email to ops@
ADVANCED: attempt to remediate
✓the alert (i.e. run a custom script
that spins up additional ec2
instances)
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50. HANDLERS
Let’s configure an EMAIL handler
✓to send a informative email for an
event.
✓
/etc/sensu/handlers/mailer.rb
plugin is installed for you, we just
need to configure and install it
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51. CONFIGURE THE
PLUGIN
ON SENSU SERVER:
vim /etc/sensu/conf.d/handlers/
mailer.json
{
"mailer": {
"mail_from": "sensu@you.com",
"mail_to": "you@yourdomain.com"
}
}
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52. CONFIGURE THE
HANDLER
cp /etc/sensu/conf.d/handlers/
default.json
/etc/sensu/conf.d/handlers/
email.json
vim /etc/sensu/conf.d/handlers/
email.json
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53. EMAIL.JSON
"handlers": {
"email": {
"type": "pipe",
"command": "/etc/sensu/handlers/
mailer.rb"
}
}
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54. CHECK GEM
DEPENDENCIES
/opt/sensu/embedded/bin/gem list | grep mail
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55. FIX PERMISSIONS
chown -R .sensu /etc/sensu/conf.d/
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56. RESTART
SERVICES
service sensu-server restart
tail -100 /var/log/sensu/sensu-server.log
| grep mail
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57. CHECKS
Sensu-client runs CHECKS that
✓defined and scheduled either are
locally (standalone) or on the
sensu-server (subscription).
A CHECK sends a RESULT as
✓EVENT to a HANDLER - this an
applies to anything - service
checks, metrics, etc
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58. CHECK
EXECUTION
✓
Either scheduled by the server
(subscription) or scheduled by the
client (standalone)
Today we will configure a
✓subscription-based check on the
server that will run on our client
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59. LETS CONFIGURE
A CHECK
✓
Use check-procs.rb to make sure
at least one instance of cornbread
is running
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60. DETERMINE OUR
CHECK COMMAND
On your SENSU CLIENT:
/opt/sensu/embedded/bin/ruby /etc/sensu/plugins/check-procs.rb -p
cornbread -W1
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61. INSTALL OUR
CHECK
✓On your SENSU SERVER:
vim /etc/sensu/conf.d/checks/
✓cornbread_process.json
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62. CORNBREAD_PRO
CESS.JSON
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63. RESTART
SERVICES
service sensu-server restart
tail -100 /var/log/sensu/sensu-server.log
| grep cornbread
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64. CHECK YOUR
DASHBOARD
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65. CHECK YOUR
EMAIL
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66. SENSU API
✓
✓HTTP/4567
on SENSU SERVER try:
✓
REST API
curl -l http://localhost:4567/events
| python -mjson.tool
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67. SENSU SERVICES
✓Sensu API
Sensu Server
✓
✓Sensu Client
Sensu Dashboard
✓
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68. EVERYTHING OK?
✓
/etc/init.d/sensu-service {client|
server|api|dashboard} {start|stop|
status|restart}
✓ps -ef | grep sensu
tail -f /var/log/sensu/*.log
✓
✓curl -l localhost:4567/info
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69. COOL SENSU
TRICKS
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70. SEND DIRECTLY
TO SENSU
netcat to: 127.0.0.0:3030
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71. AGGREGATE
ALERTS
✓
Alert when
✓not OK X% of checks are are
Handy for preventing alert floods
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72. MY SENSU TIPS
install the RabbitMQ management
✓web interface and bookmark it (see
http://10.254.254.10:15672/#/ )
✓
lock your plugins’ gem
dependency versions
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73. TIPS TIPS TIPS
✓
have alternate ways to access your
Dashboard information
✓
we integrated our command-line
developer tools with Sensu API
✓
we also created our own Ops
dashboard that queries Sensu,
Graphite and our app for data
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74. MORE TIPS
✓
Put NGINX in front of sensudashboard
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75. HA SENSU
✓
Redundancy is easy (bring up
more sensu-servers)
✓
Making Redis and RabbitMQ HA
more challenging
✓
We’re still running one solitary
Redis and RabbitMQ but are OK
with this risk for now
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76. WHERE TO GO
FOR HELP
✓
✓IRC: #sensu - freenode
sensu-users mailing list
✓
http://docs.sensuapp.org
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77. QUESTIONS
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78. THANK YOU
bethany@paperlesspost.com
@skymob - twitter
robotwitharose - #sensu on IRC (freenode)
Thursday, November 14, 13