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etcd - mission-critical key-value store - OSCON...

etcd - mission-critical key-value store - OSCON 2016

Brandon Philips

May 20, 2016
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  1. Motivation CoreOS cluster reboot lock - Decrement a semaphore key

    atomically - Reboot and wait... - After reboot increment the semaphore key
  2. Requirements Strong Consistency - mutual exclusive at any time for

    locking purpose Highly Available - resilient to single points of failure & network partitions Watchable - push configuration updates to application
  3. Common problem GFS Paxos Big Table Spanner CFS Chubby Google

    - “All” infrastructure relies on Paxos
  4. Common problem Amazon - Replicated log powers ec2 Microsoft -

    Boxwood powers storage infrastructure Hadoop - ZooKeeper is the heart of the ecosystem
  5. w = Watch(foo) for { r = w.Recv() print(r.Event) //

    PUT print(r.KV) // foo,bar } Streaming Watch
  6. Reliable Performance - Similar to ZooKeeper with snapshot disabled -

    Incremental snapshot - No Garbage Collection Pauses - Off-heap storage
  7. Reliability 99% at small scale is easy - Failure is

    infrequent and human manageable 99% at large scale is not enough - Not manageable by humans 99.99% at large scale - Reliable systems at bottom layer
  8. Write Ahead Log Append only - Simple is good Rolling

    CRC protected - Storage & OSes can be unreliable
  9. Snapshots Torturing DBs for Fun and Profit (OSDI2014) - The

    simpler database is safer - LMDB was the winner Boltdb an append only B+Tree - A simpler LMDB written in Go
  10. Testing Clusters Failure Inject failures into running clusters White box

    runtime checking - Hash state of the system - Progress of the system
  11. etcd/raft Reliability Designed for testability and flexibility Used by large

    scale db systems and others - Cockroachdb, TiKV, Dgraph