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Building Distributed Systems With Riak and Riak Core
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Building Distributed Systems With Riak and Riak Core


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My talk from DevNationSF 2010

My talk from DevNationSF 2010

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  • 1. Building Distributed Systems With Riak Core Andy Gross (@argv0) VP Engineering Basho DevNation SF 2010
  • 2. Riak K/V • Distributed Key-Value Store • Based on Amazon’s Dynamo • HTTP and Binary (Protocol Buffers) APIs • Data access by {Bucket, Key} • Javascript Map/Reduce • Link Walking • Pluggable Storage (Bitcask, InnoDB, ...)
  • 3. High-Level Dynamo • Decentralized (no “master” nodes) • Homogeneous (all nodes can do anything) • Vector clocks (no reliance on physical time) • Gossip Protocol (no global state) • Consistent Hashing for replica placement (a local calculation for each node)
  • 4. N, R, W Values • N = number of replicas to store (on distinct nodes) • R = number of replica responses needed for a successful read (specified per-request) • W = number of replica responses needed for a successful write (specified per- request)
  • 5. Harvesting A Framework • We noticed that Riak code fell into one of two categories • Code specific to K/V storage • “generic” distributed systems code • So we split Riak into K/V and Core
  • 6. Distributed Coordination • Making many machines act like one • Division of labor • Load balancing • State storage • Mutual exclusion/locking
  • 7. Riak Core Applications Your App Riak K/V Riak Core
  • 8. Riak Core Applications Your App Your App Riak K/V Riak Core
  • 9. Riak Core Abstractions • Virtual Nodes • Preference Lists • Ring Event Watchers • Node Event Watchers
  • 10. Virtual Nodes • Primary actor in a Dynamo-based system • Handles load for (1/num_partitions) • Implements commands dispatched from clients • Handles handoff when nodes join/leave
  • 11. Preference Lists • Lists of virtual nodes obtained by hashing a request (document, sessionid, etc). • Allows any node to compute document locations • Central to replication in Riak • Down nodes are filtered out, replaced with next-best nodes in the ring.
  • 12. Ring Event Watchers • Notified when ring state changes due to node addition/removal • API: ring_update(NewRing) • Can modify ring state in an app-specific fashion
  • 13. Node Event Watchers • Nodes run and advertise “services” • API: service_update(Services) • Active service list used to generate per-app preference lists.
  • 14. Use cases • If distributed systems isn’t your core business, outsource it! • Providing a distribution layer on top of non-distributed systems like: • Couch, Redis, Memcached • Implementing your own systems.
  • 15. Current Status and Roadmap • Erlang-only now, but not for long (HTTP and PB APIs coming) • Some harvesting left to do (versioned objects, ring/node handler utilities) • Project templates - skeleton code for writing Riak Core-based systems. • Stronger consistency models (with a Paxos/ ZAB-like protocol)
  • 16. Thanks! • • • • irc:// • Riak SF Meetup (on • Visit us! 795 Folsom @ 4th (Twitter Bldg.)