sensu at nycdevops meetup

SENSE AND SENSU-BILITYPainless Metrics And Monitoring

In The Cloud with Sensu

Bethany Erskinenycdevops Meetup

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

Thursday, November 14, 13

DO YOU LOVE YOUR

MONITORING SETUP?

Thursday, November 14, 13

#MONITORINGLOVE

Thursday, November 14, 13

MY STORY

+

(╯（╰,)

Thursday, November 14, 13

Thursday, November 14, 13

Thursday, November 14, 13

WHY SENSU

✓Ruby

✓Plugins can be written in any language

✓sensu-chef cookbook

✓community

Thursday, November 14, 13

WHY SENSU

✓re-use Nagios checks

✓metrics and checks all collected by one system

✓Graphite integration

✓easy to scale

Thursday, November 14, 13

WHY SENSU

✓“Can I do X with Sensu?” probably!

Thursday, November 14, 13

WHY SENSU

Thursday, November 14, 13

WHY SENSU?

✓Sensu source is well-written and easy to parse

✓https://github.com/sensu

Thursday, November 14, 13

WHY SENSU?

✓sensu-community-plugins

✓80 contributors

✓over 600 plugins

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

Thursday, November 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

Thursday, November 14, 13

RESOURCES✓All of our Sensu infrastructure is

virtualized.

✓We typically give a sensu-server box 1.5GB RAM and 4 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)

Thursday, November 14, 13

AS WE GREWGrowing pains and lessons learned...

Thursday, November 14, 13

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

Thursday, November 14, 13

HOW TO SCALE

✓Add more sensu-server instances

✓No special configuration needed

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

Thursday, November 14, 13

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

Thursday, November 14, 13

GRAPHITE PAINS

✓Solution: stop collecting metrics every 10 seconds (excessive!)

✓moved staging metrics to staging Graphite cluster

✓Moved prod Graphite cluster to SSD

Thursday, November 14, 13

THE MIGRATIONor, How To Quit Nagios in Ten Easy Steps

Thursday, November 14, 13

STEP 1: NUKE AND PAVE

Thursday, November 14, 13

STEP 2: PLANMETRICS AND MONITORING SURVEY

Thursday, November 14, 13

METRICS AND MONITORING SURVEY

Thursday, November 14, 13

STEP 3: DEFINE GLOBALS

✓CHECKS: must be actionable!

✓METRICS: go nuts

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

Thursday, November 14, 13

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

Thursday, November 14, 13

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

Thursday, November 14, 13

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

Thursday, November 14, 13

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

Thursday, November 14, 13

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

Thursday, November 14, 13

SENSU IN CHEF

Thursday, November 14, 13

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

Thursday, November 14, 13

STEP 8: WATCH THE WATCHER

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

Thursday, November 14, 13

Thursday, November 14, 13

MONITOR THE MONITOR

✓Other ideas: have Testing Sensu monitor Prod Sensu

✓Sensu can collect metrics about itself

Thursday, November 14, 13

STEP 9: ROLLOUT

✓Deploy your Production server infrastructure

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

Thursday, November 14, 13

STEP 10: TUNE

✓Laissez le bon alertes roulent!

✓Expect to need to tune thresholds and alert occurrences.

Thursday, November 14, 13

SENSU ARCHITECTURE

Thursday, November 14, 13

SENSU ARCHITECTURE

Thursday, November 14, 13

OMNIBUS INSTALLER

is awesome

Thursday, November 14, 13

LET’S PLAY WITH SENSU

If you haven’t been able to get your sandboxes up and running,

please pair with someone near you.

Thursday, November 14, 13

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

Thursday, November 14, 13

OOPS

If you mess anything up:

vagrant halt; vagrant up

Worst case:

vagrant destroy; vagrant up

Thursday, November 14, 13

TWO VIRTUALBOXES

Sensu-Server and Sensu-ClientVagrant/Chef

Centos 6.4Sensu Version 0.10.2

Thursday, November 14, 13

SENSU CONFIGURATION

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

✓sudo su -

✓cd /etc/sensu

Thursday, November 14, 13

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}

Thursday, November 14, 13

TRIGGER AN ALERT!

On sensu-client:

service sensu-client stop

Thursday, November 14, 13

CHECK YOUR DASHBOARD

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

✓username: admin / password: secret

Thursday, November 14, 13

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”

Thursday, November 14, 13

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)

Thursday, November 14, 13

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

Thursday, November 14, 13

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

Thursday, November 14, 13

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

Thursday, November 14, 13

EMAIL.JSON

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

Thursday, November 14, 13

CHECK GEM DEPENDENCIES

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

Thursday, November 14, 13

FIX PERMISSIONS

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

Thursday, November 14, 13

RESTART SERVICES

service sensu-server restart

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

Thursday, November 14, 13

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

Thursday, November 14, 13

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

Thursday, November 14, 13

LETS CONFIGURE A CHECK

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

Thursday, November 14, 13

DETERMINE OUR CHECK COMMAND

On your SENSU CLIENT:

/opt/sensu/embedded/bin/ruby /etc/sensu/plugins/check-procs.rb -p cornbread -W1

Thursday, November 14, 13

INSTALL OUR CHECK

✓On your SENSU SERVER:

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

Thursday, November 14, 13

CORNBREAD_PROCESS.JSON

Thursday, November 14, 13

RESTART SERVICES

service sensu-server restart

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

Thursday, November 14, 13

CHECK YOUR DASHBOARD

Thursday, November 14, 13

CHECK YOUR EMAIL

Thursday, November 14, 13

SENSU API

✓REST API

✓HTTP/4567

✓on SENSU SERVER try:

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

Thursday, November 14, 13

SENSU SERVICES

✓Sensu API

✓Sensu Server

✓Sensu Client

✓Sensu Dashboard

Thursday, November 14, 13

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

Thursday, November 14, 13

COOL SENSU TRICKS

Thursday, November 14, 13

SEND DIRECTLY TO SENSUnetcat to: 127.0.0.0:3030

Thursday, November 14, 13

AGGREGATE ALERTS

✓Handy for preventing alert floods

✓Alert when X% of checks are are not OK

Thursday, November 14, 13

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

Thursday, November 14, 13

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

Thursday, November 14, 13

MORE TIPS

✓Put NGINX in front of sensu-dashboard

Thursday, November 14, 13

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

Thursday, November 14, 13

WHERE TO GO FOR HELP

✓http://docs.sensuapp.org

✓IRC: #sensu - freenode

✓sensu-users mailing list

Thursday, November 14, 13

QUESTIONS

Thursday, November 14, 13

THANK YOU

bethany@paperlesspost.com@skymob - twitter

robotwitharose - #sensu on IRC (freenode)

Thursday, November 14, 13