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We are currently developing an image processing restful api. Server performs some CPU-heavy computations image processing upon request and return the image to the client.

We want to make this a single http request (all computation should be done).

My questions.

  • What is the best workflow for this. With speed has an high factor.

  • Other alternatives suggest using a Master/Worker Server workflow. But will mean multiple requests (first to put job in queue, others to poll if job is done). We want to make it a one trip request. How can we achieve this?

  • The single request would most definitely take some time how do we handle timeouts

One more thing, we are using NodeJS.

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  • A Restful API that has only one http call is not a restul API. What's the execution time of the processing? Just to get an idea. Does it run in a millisecond? a second? or a minute? Are you using GPUs or fancy hardware? – cauchy Dec 4 '15 at 12:52
  • Lets say little seconds. AWS Architecture, can always scale up – Tom Peach Dec 4 '15 at 13:25
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    If I understand nodejs correctly, it is not the ideal server for blocking CPU heavy calls as it will cause the queue to pile up under heavy load. – user40980 Dec 4 '15 at 16:02
  • Why do you want it all in one request? The time for making a request between machines will be nothing compared to the time the CPU will take to process the image, so you are better sharing the jobs out amoung multiple machines. – Cormac Mulhall Dec 11 '15 at 14:05
  • Thanks @CormacMulhall, Already implemented a web-worker model for it. Had two separate machines (will definitely scale them up). One for receiving the request, the other for processing like TMN suggested – Tom Peach Dec 13 '15 at 5:05
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You should submit your requests using a POST, and your service should return a URL that will retrieve the image once it's been processed. If the URL is accessed before the processing is complete, you should return a 202 (ACCEPTED) response. Once processing is complete, you can serve the processed image.

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  • Thanks TMN. I will add Worker Server to the workflow, and queue up image processing jobs there. – Tom Peach Dec 4 '15 at 14:11

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