Reactive Data Access with RxJava... and N1QL!

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Reactive Data Access with RxJava …and N1QL! Michael Nitschinger, Couchbase Inc. @daschl

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©2016 Couchbase Inc. 2 § New challenges §  React to user load §  React to failure §  Be responsive under load and failure § Need new solutions §  Decoupled, event-driven architectures §  Optimal resource utilization Reactive? 2

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RxJava 101 A Gentle Introduction

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©2016 Couchbase Inc. 12 §  Java implementation for Reactive Extensions https://github.com/ReactiveX §  A library to compose asynchronous and event-driven programs through observable sequences. RxJava: Introduction single multiple sync T Iterable async Future Observable 12

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©2016 Couchbase Inc. 13 §  Observables are the duals of Iterables §  They describe both Latency and Error side eﬀects. RxJava: Introduction event Iterable (pull) Observable (push) data retrieval T next() onNext(T) error discovery throws Exception onError(Exception) completion returns onCompleted() 13

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Reactive N1QL Cranking Queries up to Eleven!

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©2016 Couchbase Inc. 33 § Simple §  Executes a single N1QL statement, no options available. § Parameterized §  Executes a parameterized query with positional or named params §  Prepared Query supported through adhoc(false) Query Types 33

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©2016 Couchbase Inc. 34 § (Async) N1qlQueryResult §  Observable rows() §  Observable errors() §  Observable info() §  Observable signature() §  Observable ﬁnalSuccess() §  Observable status() §  boolean parseSuccess() §  String requestId() §  String clientContextId() Query Response 34

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Error Handling with RxJava

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©2016 Couchbase Inc. 43 § Things will go wrong, so better plan for it § Do not trust integration points (including the SDK) § Synchronous retry & fallback is too damn hard § RxJava provides (almost) everything you need to §  fallback §  retry §  fail fast Preparing to Fail 43

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©2016 Couchbase Inc. 44 Timeouts 44 § The network is unreliable § Servers fail § The SDK contains bugs § Always specify timeouts and deal with them! § The synchronous wrapper deﬁnes them for you all the time.

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©2016 Couchbase Inc. 49 Coordinated Retry 49 §  Fail fast §  Don’t let your system get stuck §  Shed load with backpressure § Retry §  immediately won’t help §  either linear or exponential back-oﬀ necessary §  have a strategy if retry also doesn’t work (Fallbacks!)