reactive data acces with rxjava, including n1ql: couchbase connect 2015

REACTIVE DATA ACCESS WITH RXJAVA… INCLUDING N1QL!

Michael Nitschinger, Couchbase@daschl

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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?

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Why Reactive?

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Detour: Async Java Client Stack

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Detour: Smart Batching

Source: http://mechanical-sympathy.blogspot.co.at/2011/10/smart-batching.html5

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Detour: Smart Batching

Source: http://mechanical-sympathy.blogspot.co.at/2011/10/smart-batching.html6

RxJava 101A Gentle Introduction

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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<T>

async

Future<T>

Observable<T>

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Observables are the duals of Iterables They describe both Latency and Error side

effects.

RxJava: Introduction

event Iterable<T> (pull) Observable<T> (push)

data retrieval

T next() onNext(T)

error discovery

throws Exception onError(Exception)

completion returns onCompleted()

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Consuming Observables

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The Observer subscribes and receives events.

A cold Observablestarts when subscribed.

onNext can be called0..N times

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RxJava: Creating Observables

just

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RxJava: Creating Observables

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RxJava: Creating Observables

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RxJava: Creating Observables

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RxJava: Creating Observables

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RxJava: Creating Observables

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RxJava: Transforming Observables

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RxJava: Transforming Observables

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RxJava: Transforming Observables

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RxJava: Transforming Observables

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RxJava: Transforming Observables

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RxJava: Transforming Observables

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RxJava: Transforming Observables

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RxJava: Transforming Observables

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RxJava: Transforming Observables

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RxJava: Filtering Observables

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RxJava: Filtering Observables

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RxJava: Filtering Observables

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RxJava: Filtering Observables

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Reactive N1QLCranking Queries up to Eleven!

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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

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(Async) QueryResult Observable<AsyncQueryRow> rows() Observable<JsonObject> errors() Observable<QueryMetrics> info() Observable<Object> signature() Observable<Boolean> finalSuccess() boolean parseSuccess() String requestId() String clientContextId()

Query Response

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Simple Query

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Parameterized Query

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Named Params

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Parametrized Query

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Positional Params

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Prepared Query

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Index Handling

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Index Handling

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Conditional Index Creation

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Error Handlingwith RxJava

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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

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Timeouts

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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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Timeouts: Simple

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Timeouts: Synchronous API

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Timeouts: Complex Example

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Coordinated Retry

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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!)

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Coordinated Fallback

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Coordinated Retry: Builder

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Declarative API instead of complicated retryWhen

Thank you.