RxJS retry entire chain

Question

I read images from a live stream and select a batch periodically. I then send them to the server for validation. A HTTP error will be thrown if any fail validation. If that occurs I want to get a new batch of images.

this.input.getImages()
  .throttleTime(500)
  .switchMap(image =>

      new Observable<{}>(observer => {
        // Some operation
      })
      .map(i => ({ image, i }))

  ).filter(({ i }) =>  {
    // some filtering
  })
  .map(({ image }) => image)
  .take(6)
  .bufferCount(6)
  .map(images =>  // switch map??
    Observable.fromPromise(this.server.validate(images))
  )
  .retry(2)  // This only retrys the request, I want it to retry the whole chain (to get valid images)
  .subscribe(images => {
      console.log('All done')
    },
    err => {console.log(err)}
  )

The problem I'm having is that only the HTTP request gets retried since that is the new observable. There must be some way to encapsulate the beginning of the chain into a single Observable?

Answer 1

See learnrxjs - retry . The example shows everything restarting from source onwards when an error is thrown.

The page shows pipe syntax, but the JSBin shows fluid operator syntax if you prefer.

The basic pattern is

const retryMe = this.input.getImages()
  .flatMap(val => {
    Observable.of(val)
      // more operators
  })
  .retry(2);

Answer 2

简单的方法是将复杂的 observable 包装在defer 中，然后对结果 observable 使用重试。