Prophet - A peer to peer replicated disconnected database

Slide 1: Step 3: Prophet jesse@bestpractical.com clkao@bestpractical.com Friday, May 16, 2008 1

Slide 2: Cloud computing is Sharecropping. ( ) Friday, May 16, 2008 2

Slide 3: Chia-liang Kao Friday, May 16, 2008 3

Slide 4: Jesse Vincent Friday, May 16, 2008 4

Slide 5: We work together Friday, May 16, 2008 5

Slide 6: CL lives in Taipei Jesse lives in Boston Friday, May 16, 2008 6

Slide 7: Sometimes we need to work face to face Friday, May 16, 2008 7

Slide 8: TPE~BOS: 9410 mi TPE-HNL: 5,095 mi BOS-HNL: 5,069 mi Friday, May 16, 2008 8

Slide 9: Our Plan Step 1: Go to Hawaii for “work” Step 2: ??? Step 3: Prophet! Friday, May 16, 2008 9

Slide 10: The Plan Backfired We were there for 8 days We wrote 8000 lines of Perl We figured out step 2 Friday, May 16, 2008 10

Slide 11: Step 2: Build a Disconnected Syncable Database Friday, May 16, 2008 11

Slide 12: Prophet Friday, May 16, 2008 12

Slide 13: Prophet A semirelational, peer to peer replicated, disconnected, versioned, property database with self-healing conflict resolution Friday, May 16, 2008 13

Slide 14: Bribery! Two tshirts. If you write a (real) patch for Prophet during this talk, you get a tshirt. Send patches to jesse@bestpractical.com Friday, May 16, 2008 14

Slide 15: Getting Prophet Prophet http://code.bestpractical.com/bps-public/Prophet/ SD http://code.bestpractical.com/bps-public/sd/ Friday, May 16, 2008 15

Slide 16: What do all those buzzwords mean? Friday, May 16, 2008 16

Slide 17: semirelational Joins are expensive No backend Join support (yet) Friday, May 16, 2008 17

Slide 18: peer-to-peer replicated Update any replica Pull from any replica Push to any replica Publish a replica Changes will propagate Friday, May 16, 2008 18

Slide 19: disconnected Real-time replication is hard to scale It only works in the cloud I don't live in the cloud I want my data when I'm offline Prophet sync can happen whenever Friday, May 16, 2008 19

Slide 20: versioned Compare a record to any point in the past All changes fully logged Undo changes Use history to be smart Friday, May 16, 2008 20

Slide 21: property database Atomic operations CREATE, READ, UPDATE, DELETE, SEARCH Record types can have optional validation and canonicalization Records of the same type do not need to have the same properties Add and remove properties at will Friday, May 16, 2008 21

Slide 22: self-healing conflict resolution Remembers all conflict resolutions Syncs all resolutions with your peers Detects identical conflicts Uses your peers’ resolutions to “vote” for the winner of a conflict Friday, May 16, 2008 22

Slide 23: What could you build with Prophet? Friday, May 16, 2008 23

Slide 24: sd A bug tracker: “simple defects” • id. Status, Summary • History • Comments • Attachments Friday, May 16, 2008 24

Slide 25: ./bin/sd ticket create --summary "Can't sync sd with Google Code" --status new Created ticket 93BF979E-08C1-11DD-94C3-D4B1FCEE7EC4 Friday, May 16, 2008 25

Slide 26: ./bin/sd ticket search --regex . 93BF979E-08C1-11DD-94C3-D4B1FCEE7EC4 Can't sync sd with Google Code new Friday, May 16, 2008 26

Slide 27: ./bin/sd ticket update --uuid 93BF979E-08C1-11DD-94C3-D4B1FCEE7EC4 --status resolved ./bin/sd ticket search --regex . 93BF979E-08C1-11DD-94C3-D4B1FCEE7EC4 Can't sync sd with Google Code resolved Friday, May 16, 2008 27

Slide 28: Bugs on my laptop aren’t interesting. Friday, May 16, 2008 28

Slide 29: Syncable! Jesse ./bin/sd publish /tmp/mybugs scp -rvp /tmp/mybugs my.com:public_html/sd CL ./bin/sd pull prophet:http://my.com/~jesse/sd Friday, May 16, 2008 29

Slide 30: My project has a bug tracker Friday, May 16, 2008 30

Slide 31: My project has a bug tracker Actually, mine use two: • RT • hiveminder.com Friday, May 16, 2008 30

Slide 32: Foreign Replicas Prophet makes Foriegn Replicas easy SD gets them "for free" Friday, May 16, 2008 31

Slide 33: Wrote an RT Replica for SD (Using only the public REST API) It took an afternoon Mirror an RT instance into SD Share it with your peers using prophet Sync changes back from your peers to RT Supports Comments and Attachments Friday, May 16, 2008 32

Slide 34: ...and one for Hiveminder (Using only the public REST API) Friday, May 16, 2008 33

Slide 35: I can sync my bugs with RT or Hiveminder Friday, May 16, 2008 34

Slide 36: Actually, it’s better Friday, May 16, 2008 35

Slide 37: I can sync between RT and Hiveminder Friday, May 16, 2008 36

Slide 38: I can sync between two different RTs, too Friday, May 16, 2008 37

Slide 39: We need more replica definitions: • • Trac GNATS • • Google Code What else? • SourceForge • Bugzilla • Jira • GForge • debbugs Friday, May 16, 2008 38

Slide 40: What can you use Prophet for? Friday, May 16, 2008 39

Slide 41: All your “little” databases Friday, May 16, 2008 40

Slide 42: All the databases you want while offline. • • CRM Blog • Bug tracking • Trading Card Database • Sales orders • Ideas? • Phone book Friday, May 16, 2008 41

Slide 43: “Private” Social Networks How about a P2P BBS? Prophet doesn’t need a server. You can sync over sneakernet. Friday, May 16, 2008 42

Slide 44: A look inside Prophet Friday, May 16, 2008 43

Slide 45: Terms and Concepts • • Database Property Change • • Database Replica Conflict • • “Foreign” Replica Resolution • • Record Nullifcation Change Set • • Record Type Resolution Change Set • • Change Set Merge • • Change Merge Ticket Friday, May 16, 2008 44

Slide 46: Database Backends Friday, May 16, 2008 45

Slide 47: The Record Store Stores indivdual records by type Friday, May 16, 2008 46

Slide 48: The Changeset Store Stores each atomic change to a set of records Replaying all changesets will create an exact clone of the replica Friday, May 16, 2008 47

Slide 49: Native Replica Types Friday, May 16, 2008 48

Slide 50: Subversion Slow Steady Robust Supports remote sync Requires Subversion Perl Bindings Friday, May 16, 2008 49

Slide 51: Filesystem Readable Flat files Compact Fast (Not yet fully atomic) Friday, May 16, 2008 50

Slide 52: HTTP Designed to let you “publish” databases Flat-files, Currently read-only. Same format as the filesystem replica type. Friday, May 16, 2008 51

Slide 53: “Foreign” replicas Will usually be app specific All current examples are in SD Friday, May 16, 2008 52

Slide 54: Synchronization Friday, May 16, 2008 53

Slide 55: Publish Serialize and export all of a replica's resolutions and changesets Friday, May 16, 2008 54

Slide 56: Pull Integrate unseen resolutions and then unseen changesets from a replica Friday, May 16, 2008 55

Slide 57: Push Integrate new resolutions and changesets into a replica Friday, May 16, 2008 56

Slide 58: Resolving Conflicts Figures out the best resolution “Nullifies” the conflict so the changeset can be cleanly integrated Integrates the conflicting changeset Records the resolution as a new changeset Records the resolution decision in the resolution database Friday, May 16, 2008 57

Slide 59: “The Best Resolution” Prophet has clever ways to figure out the best resolution. If there are previous resolutions for the same conflict and a majority agree, use that If the merger has specified a “prefer this side” choice, use that Prompt the user to make a decision, giving them info about previous decisions for this conflict Friday, May 16, 2008 58

Slide 60: We don't have a proof for the algorithm yet We do have dozens of runs of randomized testing. So far, it always stabilizes sanely. Friday, May 16, 2008 59

Slide 61: How does it scale? Vertical scale is boring Designed to scale to many peers You are not Google Current target is databases of O(50k) records Friday, May 16, 2008 60

Slide 62: How does it scale? Vertical scale is boring Designed to scale to many peers You are not Google Does anyone here work for Google? Current target is databases of O(50k) records Friday, May 16, 2008 60

Slide 63: Why not, then? We just have a political agenda. Web 2.0 is not Open Source. Your data shouldn’t be ‘exportable’ from the cloud. You should always have full control. So we dont need to store 10 billion records in one database. Friday, May 16, 2008 61

Slide 64: (Do you have 10 billion bugs, customer contacts or sales orders?) Friday, May 16, 2008 62

Slide 65: That said, we'd love to see a scalable, high performance prophet replica store Friday, May 16, 2008 63

Slide 66: Project Status Simple, well-defined Perl API RESTy web API (with microserver) Fast, lightweight backend Small, active dev community Great test coverage Horrible POD coverage Friday, May 16, 2008 64

Slide 67: Our Plans Improved search and indexing (Including full-text indexing) Query language Proper security model Jifty, Catalyst, Rails models? Friday, May 16, 2008 65

Slide 68: Prophet is very young Many, many hours of design About 10 days of two hackers hacking Friday, May 16, 2008 66

Slide 69: Codebase Prophet 5479 lines of code and doc 1693 lines of tests sd 1695 lines of code and doc 876 lines of tests Friday, May 16, 2008 67

Slide 70: Getting Prophet Prophet http://code.bestpractical.com/bps-public/Prophet/ SD http://code.bestpractical.com/bps-public/sd/ Friday, May 16, 2008 68

Slide 71: Getting Involved prophet-subscribe@lists.bestpractical.com #prophet on freenode IRC Friday, May 16, 2008 69

Slide 72: Thanks! Friday, May 16, 2008 70