How to avoid overlapping requests when doing periodic requests with RxJava

Question

I would like to use RxJava (RxJava2 actually) to periodically send network (HTTP) requests. A first attempt would look more or less like this (adapted from this source):

Observable.interval(5, TimeUnit.SECONDS, Schedulers.io())
          .map(tick -> sendNetworkRequest())

This will call sendNetworkRequest every 5 seconds.

However if sendNetworkRequest() takes some time to complete (for example on a slow network, or if there are multiple retries..) the requests would overlap.

What I would like to do is to make sure there is an interval of 5 seconds between requests, i.e. from the end of the previous request to the start of the next one.

How can this be accomplished with RxJava?

Answer 1

Use repeatWhen

    Observable.fromCallable(sendNetworkRequest())
              .repeatWhen(observable -> observable.delay(5, TimeUnit.SECONDS));