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Who am I ? What am I doing here?

Who am I ? What am I doing here?. Twitter: @ mcwoods Email: chris.woods@mind-flip.com Mind-Flip Blog: www.mind-flip.com/theBlog Linked In: http :// www.linkedin.com/in/mindflip When I think I’m being profound, or funny: www.WithBigHair.com. Birth of an Idea…. Application Design.

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Who am I ? What am I doing here?

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  1. Who am I ? What am I doing here? • Twitter: @mcwoods • Email: chris.woods@mind-flip.com • Mind-Flip Blog:www.mind-flip.com/theBlog • Linked In: http://www.linkedin.com/in/mindflip • When I think I’m being profound, or funny: www.WithBigHair.com

  2. Birth of an Idea…

  3. ApplicationDesign

  4. Application Design

  5. Data Structure Design • Resulting Structures • User Object • Feed Object • Story Object • Comment Object

  6. WWR: VocZie’s Object linking Feed Object User Object 1 * 0..1 1 1 1 Comment Object 1 Story Object 1

  7. VocZie’s REST API Examples: • /feeds/<feed_id> • /feeds/<feed_id>/stories • /feeds/<feed_id>/story/<story_id>/comments • /feeds/<feed_id>/story/<story_id>

  8. Selecting a Technology

  9. MongoDB Structures • Collections • Objects and their identity • The two ways of relating objects • Via pointers (aka _id) • Via embedding

  10. Transaction Problem? UpdateStoriesFromFeed( url ) if ( url is being updated ) then wait for notification else lock out everyone else from updating url fetch and parse stories from feed’s url for each story returned if ( story doesn’t already exist in DB) add story end if end for remove lock preventing anyone else from updating url end if End function

  11. Implementing a lock manually • update if current • Aka Compare and Swap • Atomic MongoDB actions allow for manual creation of locks • http://www.mongodb.org/display/DOCS/Atomic+Operations#AtomicOperations-TheABANuance

  12. Stumbling along

  13. Moment of Terror 500 – Internal server error. There is a problem with the resource you are looking for, and it cannot be displayed.

  14. More Terror root@1310-1064-2283:~# mongod mongod --help for help and startup optionsMon Jul 23 14:38:35 [initandlisten] MongoDB starting : pid=26105 port=27017dbpath=/data/db/ 64-bit** WARNING: You are running in OpenVZ. This is known to be broken!!!

  15. The Technical Lesson • VMs change over time…

  16. More More Terror…. • Have I lost all my data ? • Can I back up now?

  17. cat Terror | less • The no backup – backup… • Check out /var/lib/mongodb

  18. Conclusions • Good • No SQL DB is great for avoiding the DAL translation pain • Aid development time • MongoDB Core Documentation is good • Bad • Small print – VM compatibility • MongoDB Driver Documentation isn’t as good as the core

  19. Questions ? • Twitter: @mcwoods • Email: woods.mc@gmail.com • Mind-Flip Blog:www.mind-flip.com/theBlog • Linked In: http://www.linkedin.com/in/mindflip • When I think I’m being profound, or funny: www.WithBigHair.com

  20. Application Design • User Functionality First • What data does the UI need? • What structure would best present that data?

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