How do I - Long polling and Schedulers?

问题

I am trying to schedule a long polling mechanism. And I was wondering if I could leverage Schedulers for that.

Here's what I have been thinking so far.

1. Schedule via timer, but only enqueue next iteration if previous iteration has already finished.

2. Enqueue next iteration as previous iteration is finishing.

I have been looking at existing schedulers, but I am not really sure which one to pick and what to overload.

And last but not least - as I am a novice in Rx world - what are the advantages that the use of Scheduler would offer vis-a-vis "roll your own" approach.

回答1:

Something like this:

Observable.interval(500)
.exhaustMap(() => this.load()) //previously flatMapFirst, creates new observable only if previous has ended
.map(r => resource.json)
.distinctUntilChanged() //optional tracking changes
.startWith(0); 

来源：https://stackoverflow.com/questions/37926371/how-do-i-long-polling-and-schedulers