SENSE AND SENSU-BILITYPainless Metrics And Monitoring

In The Cloud with Sensu

Bethany ErskineVelocity NYC 2013

http://github.com/skymob/sensu-tutorial

Monday, October 14, 13

BEFORE I BEGIN...IF YOU DID NOT SET UP SENSU-TUTORIAL

BEFORE THE CLASS:

1. grab a USB key 2. follow the instructions on the README

If you don’t have a computer, no sweat!

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DO YOU LOVE YOUR

MONITORING SETUP?

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#MONITORINGLOVE

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MY STORY

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(╯（╰,)

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WHY SENSU

✓Ruby

✓Plugins can be written in any language

✓sensu-chef cookbook

✓community

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WHY SENSU

✓re-use Nagios checks!

✓metrics and checks all collected by one system

✓Graphite integration

✓easy to scale

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WHY SENSU

✓“Can I do X with Sensu?” probably!

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WHY SENSU

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WHY SENSU?

✓Sensu source is well-written and easy to parse

✓https://github.com/sensu

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WHY SENSU?

✓sensu-community-plugins

✓80 contributors

✓over 600 plugins

✓https://github.com/sensu/sensu-community-plugins

Monday, October 14, 13

TODAY at PAPERLESS

Two Sensu environments (prod/testing)~ 250 - 275 instances of sensu-client

4-6 Sensu-server instances25k Metrics/Hour to Graphite

1 custom dashboard1 custom CLI

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RESOURCES✓All of our Sensu infrastructure is

virtualized.

✓We typically give a sensu-server box 1.5GB RAM and 2 processors, scaling up RAM for any box running more than one Sensu service on it.

✓ 4GB RAM for a monolithic Sensu install (Rabbit, Redis, all Sensu components on one)

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AS WE GREWGrowing pains and lessons learned...

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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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HOW TO SCALE

✓Add more sensu-server instances

✓No special configuration needed

✓checks will be distributed in round-robin fashion to the sensu-servers

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GRAPHITE PAINS

✓symptoms: backed up queues in RabbitMQ, spotty graphs

✓cluster couldn’t keep up with the large amount of metrics we were now serving it via AMQP

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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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THE MIGRATIONor, How To Quit Nagios in Ten Easy Steps

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STEP 1: NUKE AND PAVE

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STEP 2: PLANMETRICS AND MONITORING SURVEY

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METRICS AND MONITORING SURVEY

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STEP 3: DEFINE GLOBALS

✓CHECKS: must be actionable!

✓METRICS: go nuts

✓HANDLERS: EMAIL for everything initially, added Pagerduty later.

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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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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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STEP 5: SET UP A PLACE TO TEST

✓Set up a permanent testing Sensu stack using your CM tool of choice

✓we used sensu-chef cookbook

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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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EXAMPLE WORKFLOW

✓add new sensu_check definitions to the appropriate cookbook in Chef

✓deploy new check to staging env using Chef

✓Pull Request with sample graphs or alerts

✓Code Review from colleague

✓Deploy to Prod

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SENSU IN CHEF

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STEP 7: EXECUTE WORKFLOW

✓Starting with the low-hanging fruit (plugins that already existed in 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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STEP 8: WATCH THE WATCHER

✓Set up some bare-minimum 3rd party monitoring for the Sensu servers

✓We use Panopta’s agent to check for aliveness, disk usage and CPU usage.

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MONITOR THE MONITOR

✓Other ideas: have Testing Sensu monitor Prod Sensu

✓Sensu can collect metrics about itself

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STEP 9: ROLLOUT

✓Deploy your Production server infrastructure

✓Roll out the client and checks to the rest of the your prod environments. 

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STEP 10: TUNE

✓Laissez le bon alertes roulent!

✓Expect to need to tune thresholds and alert occurrences.

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SENSU ARCHITECTURE

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SENSU ARCHITECTURE

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OMNIBUS INSTALLER

is awesome

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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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SANDBOX GOALS✓Get familiar with Sensu

configuration

✓Install a Handler

✓Deploy a check

✓Trigger an alert on that check

✓Give you something to take home and hack on

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OOPS

If you mess anything up:

vagrant halt; vagrant up

Worst case:

vagrant destroy; vagrant up

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TWO VIRTUALBOXES

Sensu-Server and Sensu-ClientVagrant/Chef

Centos 6.4Sensu Version 0.10.2

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SENSU CONFIGURATION

✓Please open up a terminal and SSH into both your sensu-server and sensu-client VMs

✓sudo su -

✓cd /etc/sensu

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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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TRIGGER AN ALERT!

On sensu-client:

service sensu-client stop

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CHECK YOUR DASHBOARD

✓Open a web browser and go to http://10.254.254.10:8080

✓username: admin / password: secret

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HANDLERS

✓A HANDLER takes action on an event using a pipe, TCP, UDP, AMQP, or a set of other handlers

✓Examples: send an email, send event to Pagerduty, send metrics to Graphite

✓Default is “debug”

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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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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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CONFIGURE THE PLUGIN

{ "mailer": { "mail_from": "sensu@you.com", "mail_to": "you@yourdomain.com" }}

ON SENSU SERVER:vim /etc/sensu/conf.d/handlers/mailer.json

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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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EMAIL.JSON

"handlers": { "email": { "type": "pipe", "command": "/etc/sensu/handlers/mailer.rb" }}

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CHECK GEM DEPENDENCIES

/opt/sensu/embedded/bin/gem list | grep mail

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FIX PERMISSIONS

chown -R .sensu /etc/sensu/conf.d/

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RESTART SERVICES

service sensu-server restart

tail -100 /var/log/sensu/sensu-server.log | grep mail

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CHECKS✓Sensu-client runs CHECKS that are

defined and scheduled either locally (standalone) or on the sensu-server (subscription).

✓A CHECK sends a RESULT as an EVENT to a HANDLER - this applies to anything - service checks, metrics, etc

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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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LETS CONFIGURE A CHECK

✓Use check-procs.rb to make sure at least one instance of cornbread is running

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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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INSTALL OUR CHECK

✓On your SENSU SERVER:

✓vim /etc/sensu/conf.d/checks/cornbread_process.json

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CORNBREAD_PROCESS.JSON

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RESTART SERVICES

service sensu-server restart

tail -100 /var/log/sensu/sensu-server.log | grep cornbread

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CHECK YOUR DASHBOARD

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CHECK YOUR EMAIL

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SENSU API

✓REST API

✓HTTP/4567

✓on SENSU SERVER try:

curl -l http://localhost:4567/events \ | python -mjson.tool

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SENSU SERVICES

✓Sensu API

✓Sensu Server

✓Sensu Client

✓Sensu Dashboard

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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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COOL SENSU TRICKS

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SEND DIRECTLY TO SENSUnetcat to: 127.0.0.0:3030

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AGGREGATE ALERTS

✓Handy for preventing alert floods

✓Alert when X% of checks are are not OK

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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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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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MORE TIPS

✓Put NGINX in front of sensu-dashboard

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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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WHERE TO GO FOR HELP

✓http://docs.sensuapp.org

✓IRC: #sensu - freenode

✓sensu-users mailing list

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QUESTIONS

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THANK YOU

bethany@paperlesspost.com@skymob - twitter

robotwitharose - #sensu on IRC (freenode)

Monday, October 14, 13