etcd - mission-critical key-value store - CoreOS Fest 2016

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Brandon Philips @BrandonPhilips | brandon.philips@coreos.com etcd - mission-critical key-value store

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Uncoordinated Upgrades

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... ... ... ... ... ... Unavailable Uncoordinated Upgrades

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Motivation CoreOS cluster reboot lock - Decrement a semaphore key atomically - Reboot and wait... - After reboot increment the semaphore key

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3 CoreOS updates coordination

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CoreOS updates coordination 3

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... CoreOS updates coordination 2

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... ... ... CoreOS updates coordination 0

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... ... ... CoreOS updates coordination 0

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... ... CoreOS updates coordination 0

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... ... CoreOS updates coordination 0

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... ... CoreOS updates coordination 0

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... ... ... CoreOS updates coordination 0

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CoreOS updates coordination

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Store Application Configuration config

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config Start / Restart Start / Restart Store Application Configuration

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config Update Store Application Configuration

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config Unavailable Store Application Configuration

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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

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Requirements CAP - We want CP - We want something like Paxos

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Common problem GFS Paxos Big Table Spanner CFS Chubby Google - “All” infrastructure relies on Paxos

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Common problem Amazon - Replicated log powers ec2 Microsoft - Boxwood powers storage infrastructure Hadoop - ZooKeeper is the heart of the ecosystem

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COMMON PROBLEM #GIFEE and Cloud Native Solution

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10,000 Stars on Github 250 contributors Google, Red Hat, EMC, Cisco, Huawei, Baidu, Alibaba...

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THE HEART OF CLOUD NATIVE Kubernetes, Cloud Foundry Diego, Project Calico, many others

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ETCD KEY VALUE STORE Fully Replicated, Highly Available, Consistent

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PUT(foo, bar), GET(foo), DELETE(foo) Watch(foo) CAS(foo, bar, bar1) Key-value Operations

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DEMO play.etcd.io

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Runtime Reconfiguration Point-in-time Backup Extensive Metrics etcd Operationality

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ETCD v3 Successor of etcd v2

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ETCD v3 Better Performance

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ETCD v3 More Efficient APIs

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Multi-Version Put(foo, bar) Put(foo, bar1) Put(foo, bar2) Get(foo) -> bar2

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Multi-Version Put(foo, bar) Put(foo, bar1) Put(foo, bar2) Get(foo, 1) -> bar

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Tx.If( Compare(Value("foo"), ">", "bar"), Compare(Version("foo"), "=", 2), ... ).Then( Put("ok","true")... ).Else( Put("ok","false")... ).Commit() Mini-Transactions

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l = CreateLease(15 * second) Put(foo, bar, l) l.KeepAlive() l.Revoke() Leases

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w = Watch(foo) for { r = w.Recv() print(r.Event) // PUT print(r.KV) // foo,bar } Streaming Watch

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Synchronization LoC

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ETCD v2 machine coordination -> O(10k)

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ETCD v3 app/container coordination -> O(1M)

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Performance 1K keys

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Performance Snapshot caused performance degradation etcd2 - 600K keys

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Performance etcd2 - 600K keys Snapshot triggered elections

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ZooKeeper Performance Non-blocking full snapshot Efficient memory management

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Performance ZooKeeper default

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Performance Snapshot triggered election ZooKeeper default

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Performance Snapshot ZooKeeper default

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Performance GC ZooKeeper snapshot disabled

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Reliable Performance - Similar to ZooKeeper with snapshot disabled - Incremental snapshot - No Garbage Collection Pauses - Off-heap storage

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Performance etcd3 /ZooKeeper snapshot disabled

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Performance etcd3 /ZooKeeper snapshot disabled

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Memory 10GB 2.4GB 0.8GB 512MB data - 2M 256B keys

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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

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HOW DO WE ACHIEVE RELIABILITY WAL, Snapshots, Testing

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Write Ahead Log Append only - Simple is good Rolling CRC protected - Storage & OSes can be unreliable

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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

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Testing Clusters Failure Inject failures into running clusters White box runtime checking - Hash state of the system - Progress of the system

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Testing Cluster Health with Failures Issue lock operations across cluster Ensure the correctness of client library

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TESTING CLUSTER dash.etcd.io

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etcd/raft Reliability Designed for testability and flexibility Used by large scale db systems and others - Cockroachdb, TiKV, Dgraph

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etcd vs others Do one thing

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etcd vs others Only do the One Thing

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etcd vs others Do it Really Well

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etcd Reliability Do it Really Well

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ETCD v3.0 BETA Efficient and Scalable

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BETA AVAILABLE TODAY github.com/coreos/etcd

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FUTURE WORK Proxy, Caching, Watch Coalescing, Secondary Index

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GET INVOLVED github.com/coreos/etcd

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Brandon Philips @BrandonPhilips | brandon.philips@coreos.com etcd - mission-critical key-value store Thank you!