Reactive Data Access with RxJava ... and N1QL!

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REACTIVE DATA ACCESS WITH RXJAVA … INCLUDING N1QL! Michael Nitschinger, Couchbase @daschl

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©2015 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 Why Reactive? 2

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RxJava 101 A Gentle Introduction

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©2015 Couchbase Inc. 8 §  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 8

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©2015 Couchbase Inc. 9 §  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() 9

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Reactive N1QL Cranking Queries up to Eleven!

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©2015 Couchbase Inc. 31 § Simple §  Executes a single N1QL statement, no options available. § Parameterized §  Executes a parameterized query with positional or named params § Prepared §  Executed a previously prepared statement Query Types 31

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©2015 Couchbase Inc. 32 § (Async) QueryResult §  Observable rows() §  Observable errors() §  Observable info() §  Observable signature() §  Observable ﬁnalSuccess() §  boolean parseSuccess() §  String requestId() §  String clientContextId() Query Response 32

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Error Handling with RxJava

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©2015 Couchbase Inc. 41 § 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 41

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©2015 Couchbase Inc. 42 Timeouts 42 § 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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©2015 Couchbase Inc. 46 Coordinated Retry 46 §  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!)