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Capacity Management for Web Operations
 

Capacity Management for Web Operations

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    Capacity Management for Web Operations Capacity Management for Web Operations Presentation Transcript

    • Capacity Management for Web Operations John Allspaw Operations Engineering
    • the book I’m writing
    • ???
    • Rules of Thumb Planning/Forecasting Stupid Capacity Tricks (with some Flickr statistics sprinkled in)
    • Things that can cause downtime bugs (disguised as capacity problems) edge cases (disguised as capacity problems) security incidents real capacity problems* * (should be the last thing you need to worry about)
    • Capacity != Performance Forget about performance for right now Measure what you have right NOW Don’t count on it getting any better
    • Thank You HPC Industry! Automated Stuff Scalable Metric Collection/Display a lot of great deployment and management tricks come from them, adopted by web ops
    • Good Measurement Tools record and store metrics in/out custom metrics easily compare lightweight-ish I
    • Clouds need planning too Makes deployment and procurement easy and quick But clouds are still resources with costs and limits, just like your own stuff Black-boxes: you may need to pay even more attention than before
    • Metrics System Statistics
    • Metrics “Application” Level (photos processed per minute) (average processing time per photo) (apache requests) (concurrent busy apache procs)
    • Metrics App-level meets system-level here, total CPU = ~1.12 * # busy apache procs (ymmv)
    • 2400 photos per minute being uploaded right NOW (Tuesday afternoon)
    • Ceilings the most amount of “work” your resources will allow before degradation or failure
    • Forget Benchmarking
    • Find your ceilings what you have left The End
    • Use real live production data to find ceilings Production: “it’s like a lab, but bigger!”
    • Like: database ceilings replication lag: bad!
    • Ceilings waiting on disk sustained disk I/O wait for too much >40% creates slave lag* *for us,YMMV
    • 35,000 photo requests per second on a Tuesday peak
    • Safety Factors
    • Safety Factors Ceiling * Factor of Safety = UR LIMITZ
    • Safety Factors webserver!
    • Safety Factors what you have left “safe” ceiling @85% CPU 85% total CPU = ~76 busy apache procs
    • Safety Factors Yahoo Front Page link to Chinese NewYear Photos (8% spike) (photo requests/second)
    • Forecasting
    • Forecasting Fictional Example: webservers
    • Forecasting peak of the week Fictional example: 15 webservers. 1 week.
    • Forecasting ...bigger sample, 6 weeks....isolate the peaks...
    • Forecasting not too shabby now ...”Add a Trendline” with some decent correlation...
    • Forecasting this will tell you when it is ceiling when is this? what you have left 15 servers @76 busy apache proc limit = 1140 total procs
    • Forecasting (1140-726) / 42.751 = 9.68 (week #10, duh)
    • Forecasting Automation Writing excel macros is boring All we want is “days remaining”, so all we need is the curve-fit Use http://fityk.sf.net to automate the curve-fit
    • Forecasting Fictional Example: storage consumption
    • Forecasting Automation this will tell you when this is actual flickr storage consumption from early 2005, in GB (ceiling is fictional)
    • Forecasting Automation jallspaw:~]$cfityk ./fit-storage.fit cmd line script 1> # Fityk script. Fityk version: 0.8.2 output 2> @0 < '/home/jallspaw/storage-consumption.xy' 15 points. No explicit std. dev. Set as sqrt(y) 3> guess Quadratic New function %_1 was created. 4> fit Initial values: lambda=0.001 WSSR=464.564 #1: WSSR=0.90162 lambda=0.0001 d(WSSR)=-463.663 (99.8059%) #2: WSSR=0.736787 lambda=1e-05 d(WSSR)=-0.164833 (18.2818%) #3: WSSR=0.736763 lambda=1e-06 d(WSSR)=-2.45151e-05 (0.00332729%) #4: WSSR=0.736763 lambda=1e-07 d(WSSR)=-3.84524e-11 (5.21909e-09%) Fit converged. Better fit found (WSSR = 0.736763, was 464.564, -99.8414%). 5> info formula in @0 # storage-consumption 14147.4+146.657*x+0.786854*x^2 6> quit bye...
    • Forecasting Automation fityk gave: y = 0.786854x2 + 146.657x + 14147.4 ( R2 = 99.84) Excel gave: y = 0.7675x2 + 146.96x + 14147.3 ( R2 = 99.84) (SAME)
    • Capacity Health 12,629 nagios checks 1314 hosts 6 datacenters 4 photo “farms” farm = 2 DCs (east/west)
    • High and Low Water Marks alert if higher alert if lower Per server, squid requests per second
    • A good dashboard looks something like... Est limit/ ceiling limit current % days type # box units (total) (peak) peak left busy www 20 80 1600 1000 62.50% 36 procs shard I/O 20 40 800 220 27.50% 120 db wait squid 18 950 req/sec 17,100 11,400 66.67% 48 (yes, fictional numbers)
    • Diagonal Scaling vertically scaling your already horizontal nodes Image processing machines Replace Dell PE860s with HP DL140G3s
    • Diagonal Scaling example: image processing 4 cores 8 cores (about the same CPU “usage” per box)
    • Diagonal Scaling example: image processing throughput ~45 images/min @ peak ~140 images/min @ peak (same CPU usage, but ~3x more work) “processing” means making 4 sizes from originals
    • Diagonal Scaling example: image processing went from: 3008.4 1035 23U 23 Dell PE860s Watts photos/min rack to: 8 HP DL140 G3s 1036.8 Watts 1120 photos/min 8U rack !!! (75% faster, even)
    • 3.52 terabytes will be consumed today (on a Tuesday)
    • 2nd Order Effects (beware the wandering bottleneck) LB running hot, so add more www www db search memcached
    • 2nd Order Effects (beware the wandering bottleneck) LB running great now, so more traffic! now these run www www www www hot db search memcached
    • Stupid Capacity Tricks
    • Stupid Capacity Tricks quick and dirty management DSH http://freshmeat.net/projects/dsh [root@netmon101 ~]# cat group.of.servers www100 www118 dbcontacts3 admin1 admin2
    • Stupid Capacity Tricks quick and dirty management [root@netmon101 ~]# dsh -N group.of.servers dsh> date executing 'date' www100: Mon Jun 23 14:14:53 UTC 2008 www118: Mon Jun 23 14:14:53 UTC 2008 dbcontacts3: Mon Jun 23 07:14:53 PDT 2008 admin1: Mon Jun 23 14:14:53 UTC 2008 admin2: Mon Jun 23 14:14:53 UTC 2008 dsh>
    • Stupid Capacity Tricks Turn Stuff OFF Disable heavy-ish features of the site (on/off switches) We have 195 different things to disable in case of emergency.
    • Stupid Capacity Tricks Turn Stuff OFF uploads (photo) uploads (video) uploads by email various API things various mobile things various search things etc., etc.
    • Stupid Capacity Tricks Outages Happen Host your outage/status/blog page in more than one datacenter. Tell your users WTF is going on, they’ll appreciate it.
    • Stupid Capacity Tricks Hit the Pause Button Bake the dynamic into static Some Y! properties have a big red button to instantly bake (and un- bake) at will
    • thanks http://flickr.com/photos/bondidwhat/402089763/ http://flickr.com/photos/74876632@N00/2394833962/ http://flickr.com/photos/42311564@N00/220394633/ http://flickr.com/photos/unloveable/2422483859/ http://flickr.com/photos/absolutwade/149702085/ http://flickr.com/photos/krawiec/521836276/ http://flickr.com/photos/eschipul/1560875648/ http://flickr.com/photos/library_of_congress/2179060841/ http://flickr.com/photos/jekkyl/511187885/ http://flickr.com/photos/ab8wn/368021672/ http://flickr.com/photos/jaxxon/165559708/ http://flickr.com/photos/sparktography/75499095/
    • We’re Hiring! flickr.com/jobs Come see me!
    • questions?