care and feeding of large scale graphite installations - devopsdays austin 2013

Nick Galbreath http://client9.com/20130501 @ngalbreath

Care and Feeding ofLarge Scale

Graphite Installations

Nick Galbreath ★ IPONWEBDevOpsDays ★ Austin Texas ★ 2013-04-30

http://client9.com/20130501

Who is nickg?

(that's online advertising infrastructure)

• Over One Billion Points collected daily.

• In "many" independent Graphite clusters.

so, graphite?

Who cares? • Making it easy to create, analyze and

share data can change your organization

• Making a data-driven culture

• Empowering developers, operations, qa, security and business to be more confident in the changes they make.

What is it you say you do here?

• Your job is likely invisible to rest of the organization

• invisible things aren't valued

• so make what you do visible

Why Graphite?

• Many innovations in each part of the stack

• But, it's the Full Stack that really makes it special.

• On-disk layout to UI to API to... the community around it.

Sharing in Caring

• Allows data to be easily accessed

• And easily shared. This makes it different than many monitoring solutions.

• It's your own in-house mashup generator.

What is it?

The Big Picture

• It's a database

• But not ACID

• And without all the database tools

Installation• 3 python-twistd servers

• "carbon-cache"

• "cache-aggregator"

• "carbon-relay"

• Apache / Django Web UI and API

• Uses SQLite3/MySQL for dashboards / events

Be Current

• Don't use the OS default version.

• Newer point releases of graphite have significant improvements in storage engine and webui/api

• It's 100% Python so "building it yourself" shouldn't to hard.

• pip install works and is current.

The Documentation

• everyone complains about it

• historically bad, but getting a lot better

• Switched locations, but not all searchengines are updated to use:http://graphite.readthedocs.org/

• Source code is quite good, so RTFS

Storage Engine

What is it?• Storage engine

• Handles reads, writes and creates of a single metric to a fixed size file.

• One file, kinda dumb (good).

• Here's the API:https://github.com/graphite-project/whisper/blob/master/whisper.py

Graphite Math• About 12 bytes per point.

• Store 1 minute points for 1 month and 15 minutes for 11 months.

• (60×24×30 + 4×24×30×11) ×12 = 878kB

• If you can keep all your points in memory, then magic!

Disk Layout

• Each metric create a directory treeserver123.myapp.logins.failed

• Makes 3 directories

• This creates a very branchy directory structure

• This has good and bad points.

Middleware

carbon-cache

Part 1

Carbon Cache

• Metrics go in

• csv file or python pickle format

• TCP

• Metrics go to disk

• whisper

Write Buffer

• Most important feature is write buffering to protect the disk.

• Data is buffered and written out once per minute (or so).

• But

The Cache• It's a write cache.

• Once data is written, it's out of the cache

• In other words, the cache is metrics not on disk.

• If the cache dies, you lose metrics

• (btw: the read cache is the os disk cache)

New Metrics• New metrics are created automatically

• But, it is very expensive.

• MAX_CREATES_PER_MINUTE.=.50

• Saves your disk, but new metrics will "pile up" in cache.

• May take 10m+ for your metrics to start flowing....

FALLOCATE• WHISPER_FALLOCATE_CREATE.=.True

• Linux&Kernel&>=&2.6.23

• fallocate is used to preallocate blocks to a file. For filesystems which support the fallocate system call, this is done quickly by allocating blocks and marking them as uninitialized, requiring no IO to the data blocks. This is much faster than creating a file by filling it with zeros.

• https://bugs.launchpad.net/whisper/+bug/957827

Limit the SizeLimit the size of the cache to avoid swapping or becoming CPU bound.Sorts and serving cache queries gets more expensive as the cache grows.Use the value "inf" (infinity) for an unlimited cache size.

MAX_CACHE_SIZE = inf

No!.Infinity.does.not.exist.on.your.system!.&

Graphite for GraphiteBy&default,&carbon&itself&will&log&statistics&(such&as&a&count,metricsReceived)&with&the&top&level&prefix&of&'carbon'&at&an&interval&of&60seconds.&Set&CARBON_METRIC_INTERVAL&to&0&to&disable&instrumentation

CARBON_METRIC_PREFIX&=&carbonCARBON_METRIC_INTERVAL&=&60

Stats on

Stats!

Middleware

carbon-aggregator

Part 2

Pre-Aggregation• Sum or Average metrics based on

wildcards and regexps

• Helps eliminate very slow queries on webui

• You can emit the final sum & all the individual components or just the final sum (via blacklists)

destination

• r/w to localhost

• split metrics to other aggregators

• Design your own system

Along the way

• renaming of metrics

• whitelist and blacklist of aggregation and metrics

Also...

• has support for broadcasting data to multiple downstream caches

• but.. never used it.. and seems at odds with the next middleware

Middleware

carbon-relay

Part 3

It's a Router!• Consistent Hashing (Sharding)

• Or more rule-based routing

• Output to multiple carbon servers

have not really used it much, but should work similarly to scale outs of memcache, redis

Middleware

StatsDPart

StatsD• https://github.com/etsy/statsd/

• nodejs based but lots of other implementations

• Receives UDP, send graphite-compatible output, flushed periodically.

• Aggregation for all by default

• Beside sum, also can compute other basic statistics (mean, 90% percentile), do sampling, have counters, etc.

StatsD use case• It's UDP based, so it excels at

embedding a client inside the application

• UDP can't block or break the sending application

• Not so good for bulk metrics

• Use both! Can work together with aggregator.

Of Note

• https://github.com/armon/statsite

• Need to look at this more

• c + libev based

• modern time series algorithms

• very flexible output

Backups

Do you really need them?http://bit.ly/11sPhNz

Backup

• Doing naive backup causes graphite performance goes to crap.

• File system cache is trashed

• Metrics are not written to disk (lag)

• If OOM occurs then you lose metrics.

Do you need to save everything?

nice is good

http://www.beenthereyet.net/nice-france

If you are doing your own backup....

ionice is betterIONICE(1) User Commands IONICE(1)

ionice - set or get process I/O scheduling class and priority

SYNOPSIS

ionice [-c class] [-n level] [-t] -p PID... ionice [-c class] [-n level] [-t] command [argument...]

DESCRIPTION

This program sets or gets the I/O scheduling class and priority for a program. If no arguments or just -p is given, ionice will query the current I/O scheduling class and priority for that process.

When command is given, ionice will run this command with the given arguments. If no class is specified, then command will be executed with the "best-effort" scheduling class. The default priority level is 4.

Linux supports I/O scheduling priorities and classes since 2.6.13 with the CFQ I/O scheduler.

util-linux July 2011 IONICE(1)

Even Better

• Just write the metrics to two graphite servers in your client

• Script to copy / resync "holes" when restoring.

Monitoring

• Hey, it's a web server

• do all the usual stuff

• Ask for known stats,

• check for 200

• check for valid json output

Mistakes in URL or use of functions cause Server 500

Old Stats

• Don't forget to kill off old metrics

• no updates in X days? kill.

• Exercise in "find" left to reader

• If you use SQLite3 -- uhh nothing to monitor

• If you use MySQL -- use the regular suspects

• And don't forget to backup!!

CPU is stable• ... except for apache usage

• consider moving apache to separate machine

Disk is SensitiveCompeting with other processes for disk does this

Means less written to disk

Metrics updated

Dangerous build up in cache

Cache Size

Rendering

Tune Apache• By default, your Apache install is likely

to be "unlimited" in CPU and Memory usage.

• Select a wildcard metric for a long time period can easily turn a httpd process in 1GB. (this seems like a bug actually)

• OOM death.

/version/

• Yes, ending "/" is required.

• Ok not that exciting but easy check

/metrics/expand/

• /metrics/expand/?query=server*• {"results": ["server001", "server002", ... ]}

/events/

• Ad-Hoc Events that don't deserve their own metric type.

• has tags, time, and text

• Stored in SQLite3 by default by the webapp.

• Rest UI is primitive

The WebUI

• it's "ok".. good for experiments

• You will want to make your own dashboard.

• Good news! The API is a URL, so it's very easy.

WebUI Dashboards

• The WebUI has a dashboard feature for loading and saving graphs

• It saves data in SQLite3 by default

• Since it's there people will use it

• So hack to remove it or, switch to MySQL.

Granularity

• Like RRDTool, the resolution of the graph depends on number of pixels used. No sub-pixel rendering!

• Rapid spikes can be "averaged away" in week-long views in small graphs.

Vertical Line Technology

• Easy to make horizontal lines

• Not so clear how to make ad-hoc vertical lines

Turn "time since" into events

drawAsInfinite( removeAboveValue( keepLastValue( YOURMETRIC ), 120 ))

Turn Version Numbers

into EventsdrawAsInfinite( removeBelowValue( derivative(keepLastValue( YOURMETRIC)) ,0.1))

Arbitrary LinesdrawAsInfinite( removeBelowValue( removeAboveValue( time("time"), timestamp), timestamp))

Really Long URLs

• Making graph but the URL is so long browsers are clipping them?

• Send query string data as a POST

Client Side Rendering

• yeah...

• works ok with a small number of points

• crashes existing browsers with large number of points

• Server side faster in many cases!

• We'll try again in 2014

Colors and ChartJunk

• Default color scheme is gross

• Be kind to the handicapped (uhh, me)http://colorbrewer2.org/

• Good overview here:http://bit.ly/10Hu7zU

Looking for something to do?

Accelerate with PyPy

• JIT for Python

• ~ 5.9x performance improvement

• Actually works and is stable

• Compatible with twisted and Django

Accelerate with numpy

• numpy provides fast vector manipulation (C code)

• graphite web gui does a lot of vector manipulation

• hmmmm.....

Ceres Storage Engine

• "Eventually Fixed Size" storage

• More space efficient == more performance

• seehttp://blog.sweetiq.com/2013/01/using-ceres-as-the-back-end-database-to-graphite/

OpenTSB• Not Graphite, but similar in spirit

• Has "collectors" for basic ops stats

• Used by StumbleUpon, Box.net, pintrest

• Good: Stores data in HBASE/Hadoop

• Bad: Stores data in HBASE/Hadoop

Add More Functions

• coursen (I'm looking at you Ian Malpass, that's useful for client-side rendering)

• Real vertical lines (our hacks are stupid)

• Better operators (would nice to know easily how many metrics you have, e.g. select count(*))

Mine the Apache Log• Which stats are used the most?

• What are really slow queries?

• Can you optimize them?

• What time frames are used?

• How much old data do you really need to store?

it's in the

query string

Add a TinyURL Feature

• The URLs get really long and are hard to put into email, etc.

• Make a tinyurl feature into the django app and integrate into dashboard.

Write Docs

yeah you!

Nick Galbreathhttp://www.client9.com/nickg@client9.com

http://www.iponweb.com/ngalbreath@iponweb.net

Lets Make

Some Graphs!

care and feeding of large scale graphite installations - devopsdays austin 2013

nick galbreath http

ngalbreaththe cache

anunlimited cache

cache queries

read cache

cache ismetrics

ngalbreathcarbon cache

disk whisper

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