Created
January 19, 2017 10:45
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Limit concurrency with RxJS
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| // limits a stream to `limit` active events | |
| function limitStream(input$, outputComplete$, limit = 10) { | |
| const initialOutputLimiter$ = Rx.Observable.range(1, limit).map(x => true); | |
| // a stream of bools indicating when to pass the next input to the output stream | |
| const outputLimiter$ = Rx.Observable.concat(initialOutputLimiter$, outputComplete$); | |
| return Rx.Observable.zip(outputLimiter$, input$); | |
| } | |
| // Creates a responses proxy that we can pass to limitStream. | |
| // This enables our circular dependency of passing the completed responses to | |
| // the request limiter | |
| const responsesProxy$ = new Rx.Subject(); | |
| // Creates the limited stream of requests | |
| const limitedRequests$ = limitStream(requests$, responsesProxy$, 10); | |
| // We need to track each request's completion. Usually we would map limitedRequests$ | |
| // to an XHR call and end up with a responses stream but for this example We simply | |
| // map requests to `true` | |
| const responses$ = limitedRequests$.map(x => true); | |
| // Now we pipe our responses to the responsesProxy that limitedRequests$ uses to | |
| // release another request | |
| responses$.subscribe(responsesProxy$); |
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