Your SlideShare is downloading. ×
0
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Lessons Learned Migrating 2+ Billion Documents at Craigslist
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

Lessons Learned Migrating 2+ Billion Documents at Craigslist

48,226

Published on

The slides from my 2011 MongoSF talk of the same name

The slides from my 2011 MongoSF talk of the same name

Published in: Technology
0 Comments
52 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total Views
48,226
On Slideshare
0
From Embeds
0
Number of Embeds
15
Actions
Shares
0
Downloads
459
Comments
0
Likes
52
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  1. Lessons Learned from Migrating 2+ Billion Documents at Craigslist<br />Jeremy Zawodny<br />jzawodn@craigslist.org<br />Jeremy@Zawodny.com<br />http://blog.zawodny.com/<br />
  2. Outline<br />Recap last year’s MongoSV Talk<br />The Archive, Why MongoDB, etc.<br />http://www.10gen.com/video/mongosv2010/craigslist<br />The Infrastructure<br />The Lessons<br />Wishlist<br />Q&A<br />
  3. Craigslist Numbers<br />2 data centers<br />~500 servers<br />~100 MySQL servers<br />~700 cities, worldwide<br />~1 billion hits/day<br />~1.5 million posts/day<br />
  4. Archive: Where Data Goes To Die<br />Live Numbers<br />~1.75M posts/day<br />~14 day avg. lifetime<br />~60 day retention<br />~100M posts<br />We keep all postings<br />Users reuse postings<br />Daily archive migration<br />Internal query tools<br />
  5. Archive Pain<br />Coupled Schemas<br />Big Indexes<br />Hardware Failures<br />Replication Lag<br />Poor Search<br />Human Time Costs<br />
  6. MongoDB Wins<br />Scalable<br />Fast<br />Friendly<br />Proven<br />Pragmatic<br />Approachable<br />
  7. MongoDB Details<br />Plan for 5 billion documents<br />Average size: 2KB<br />3 Replica sets, 3 Servers each<br />Deploy to 2 datacenters<br />Same deployment in each datacenter<br />Posting ID is sharding key<br />
  8. MongoDB Architecture<br />Typical Sharding with Replica Sets<br />(external sphinx full-text indexers not pictured)<br />config<br />client<br />client<br />client<br />client<br />config<br />config<br />mongos<br />mongos<br />mongos<br />shard001<br />shard003<br />shard002<br />replica set<br />replica set<br />replica set<br />
  9. Lesson: Know Your Hardware<br />MongoDB on blades really sucks<br />Single 10k RPM disks can’t take it when data is noticeably larger than RAM<br />Mongo operations can hit the client timeout (30 sec default)<br />Even minutely cron jobs start to spew<br />Lots of time wasted in development environment, trying different kernels, tuning, etc.<br />Most noticeable during heavy writes but can happen if pages fall out of RAM for other reasons<br />
  10. Lesson: Replica Sets Rock<br />Lots of reboots happened during dev environment troubleshooting<br />Each time, one of the remaining nodes took over<br />No “reclone” no config file or DNS changes<br />Stuff “just worked” while nodes bounced up and down<br />
  11. Lesson: Know Your Data<br />MongoDB is UTF-8<br />Some of our older data is decidedly NOT UTF-8<br />We have lots of sloppy encoding issues to clean up. But we had to clean them all up.<br />Start data load. Wait 12-36 hours. Witness fail. Fix code. Start over. Sigh.<br />This is a combination of having been sloppy and having old data. Even with a lot less history, this can bite you. Get your encoding house in order!<br />
  12. Lesson: Know Your Data Size<br />MongoDB has a doc size limits<br />4MB in 1.6.x, 16MB in 1.8.x<br />What to do with outliers?<br />In our case, trim off some useless data.<br />But going from relational to document means this sort of problem is easy to have. One parent, many children.<br />It’d be nice if this was easier to change, but clients have it hard-coded too.<br />Compression would help, of course.<br />
  13. Lesson: Know Your Data Types<br />Field Types and Conversions can be expensive to do after the fact!<br />MongoDB treats strings and numbers differently, but some programming languages (such as Perl) don’t make that distinction obvious<br />This has indexing implications when you later look for 123456789 but had unknowingly stored “123456789”<br />http://search.cpan.org/dist/MongoDB/lib/MongoDB/DataTypes.pod<br />
  14. Data Types, continued<br />“If the type of a field is ambiguous and important to your application, you should document what you expect the application to send to the database and convert your data to those types before sending.”<br />Do you know how to do that in your language of choice?<br />Some drivers may make a “guess” that gets it right most of the time.<br />
  15. Lesson: Know SomeSharding<br />The Balancer can be your frenemy<br />Initial insert rate: 8,000/sec<br />Later drops to 200/sec<br />Too much time spent waiting to page in data that’s going to be sent to another node and never looked at (locally) again<br />Pre-split your data if possible<br />http://blog.zawodny.com/2011/03/06/mongodb-pre-splitting-for-faster-data-loading-and-importing/<br />
  16. Lesson: Know Some Replica Sets<br />Replica Set re-sync requires index rebuilds on the secondary<br />Most painful when a slave is down too long and can’t catch up using the oplog<br />Typically during high write volumes<br />In a large data set, the index rebuilding can take a couple of days w/out many indexes<br />What if you lose another while that is happening?<br />
  17. MongoDBWishlist<br />Replica set node re-sync without out index rebuilding<br />Record (or field) compression (not everyone uses a filesystem that offers compression)<br />Method to tap into the oplog so that changes can be fed to external indexers (Sphinx, Redis, etc.)<br />Hash-based sharding (coming soon?)<br />Cluster snapshot/backup tool<br />
  18. craigslist is hiring!<br />send resumes to: z@craigslist.org<br />Plain Text or PDF, no Word Docs!<br />Front-end Engineering<br />HTML, CSS, JavaScript, jQuery<br />(Mobile too)<br />Network Administration<br />Routers, switches, load balancers, etc.<br />Back-end Engineering<br />Linux, Apache, Perl, MySQL, MongoDB, Redis, Gearman, etc.<br />Systems Administration<br />Help keep all those systems running.<br />
  19. craigslist is hiring!<br />send resumes to: z@craigslist.org<br />Plain Text or PDF, no Word Docs!<br />Laid back, non-corporateenvironment<br />Engineering driven culture<br />Lots of interesting technical challenges<br />Easy SF commute<br />Excellent benefits and pay<br />High-impact work<br />Millions use craigslist daily<br />

×