CODEWITHSUNDEEP
javaasynchronousrx-javaproject-reactor
yuranos
yuranos

Reputation: 9675

Can a queue of events be persisted when using Reactor Project or RxJava

The main benefit of reactive programming is that it is fault-tolerant and can process a lot more events than a blocking implementation, despite the fact that the processing will usually happen slower.

What I don't fully understand is how and where the events are stored. I know that there is an event buffer and it can be tweaked but that buffer can easily overload the memory if the queue is unbound, can't it? Can this buffer flush onto disk? Isn't it a rist to have it in-memory? Can it be configured similarly to Lagom event-sourcing or persistent Akka actors where events can be stored in DB?

Upvotes: 1

Views: 404

Answers (1)

MightySeal
MightySeal

Reputation: 2315

The short answer is no, this buffer cannot be persisted. At least in reference implementation.

The internal in-memory buffer can hold up to 128 emited values by default, but there are some points. First of all, there is a backpressure — situatuion when the source emits items faster than observer or operator consumes them. Thus, when this internal buffer is overloaded you get a MissingBackpressureException and there are no any disk or some other way to persist it. However you can tweak the behavior, for instance keep only latest emit or just drop new emits. There are special operators for that — onBackpressureBuffer, onBackpressureDrop, onBackpressureLatest.

RxJava2 introduces a new type — Flowable which supports backpressure by default and gives more ways to tweak internal buffer.

Rx is a way to process data streams and you should care if you can consume all the items and how to store them if you can't.

One of the main advantages of rxjava is contract and there are ways to create your own operators or use some extensions like rxjava-extras

Upvotes: 1

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