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Add BlockingHttp4sServlet #1830

Merged

rossabaker merged 3 commits into http4s:master from Taig:develop

May 9, 2018

Contributor

Taig commented May 7, 2018 •

edited

The current Http4sServlet uses the async Servlet feature in its implementation. Unfortunately this is not supported in the Google App Engine (GAE) standard environment so that a blocking implementation is necessary.

Consider this PR as an initial draft. I started off by copying the Http4sServlet and ripping it apart. So there is currently quite a lot of code duplication which should be improved.

Please note that I have never worked with Servlet nor with cats.Effect before, so unfortunately some of the changes here were a bit of guesswork for me.

rossabaker reviewed May 7, 2018

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Thanks!

This is going to be unpopular, but if we move most of this into an abstract class, and leave the service method abstract, we could extend that with a small amount of code in both BlockingServlet and Http4sServlet. I prefer to avoid OO, but if we're not going to do it when implementing JEE, then where?

Alternatively, we could pass an (HttpServletRequest, HttpServletResponse) => Unit as a constructor param, but that has weird interactions with the timeout and servletIo parameters.

servlet/src/main/scala/org/http4s/servlet/BlockingHttp4sServlet.scala Outdated

  
        class BlockingHttp4sServlet[F[_]](

            service: HttpRoutes[F],

            servletIo: BlockingServletIo[F],

rossabaker May 7, 2018

Member

What's the benefit of parameterizing this? To configure the chunk size? I like that it mandates BlockingServletIo for this use case.

Taig May 8, 2018

Contributor

I wanted to keep the chunkSize configurable but also mimic the API of Http4sSevlet for consistency

servlet/src/main/scala/org/http4s/servlet/BlockingHttp4sServlet.scala Outdated

  
              )

              F.runAsync(render) {

                  case Right(_) => Sync[IO].unit

rossabaker May 7, 2018

Member

IO.unit

servlet/src/main/scala/org/http4s/servlet/BlockingHttp4sServlet.scala Outdated

  
              F.runAsync(render) {

                  case Right(_) => Sync[IO].unit

                  case Left(t) => Sync[IO].delay(errorHandler(servletResponse)(t))

rossabaker May 7, 2018

Member

IO(errorHandler(...))

servlet/src/main/scala/org/http4s/servlet/BlockingHttp4sServlet.scala Outdated

  
                .unsafeRunSync()

            } catch errorHandler(servletResponse)

          private def onParseFailure(

rossabaker May 7, 2018

Member

I think everything here below is a copy-paste and could move into an abstract class? Make them protected.

servlet/src/main/scala/org/http4s/servlet/BlockingHttp4sServlet.scala Outdated

  
            extends HttpServlet {

          private[this] val logger = getLogger

          private[this] var serverSoftware: ServerSoftware = _

rossabaker May 7, 2018

Member

Could be protected and moved to abstract class.

servlet/src/main/scala/org/http4s/servlet/BlockingHttp4sServlet.scala Outdated

  
          private[this] var serverSoftware: ServerSoftware = _

          // micro-optimization: unwrap the service and call its .run directly

          private[this] val serviceFn = service.run

rossabaker May 7, 2018

Member

Could be protected and move to abstract class. Though maybe we save a few nanoseconds going through a field (e.g., private[this]) instead of an accessor.

Contributor

Taig commented May 8, 2018

Any naming preferences for the abstract class? I would probably name it Http4sServlet and extend from AsyncHttp4sServlet and BlockingHttp4sServlet. But I assume we should not rename the current Http4sServlet for compatibility?

Taig force-pushed the Taig:develop branch from `f72899b` to `e5debd7` May 8, 2018

rossabaker reviewed May 8, 2018

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I think I can live with the breaking change on master, but that means we can't add it in the 0.18 series, and you probably want this now.

If we call the base class HttpServletLike (ugh), we could introduce BlockingHttpServlet and probably keep binary compatibility with Http4sServlet and release it in 0.18.11.

The division looks good.

Contributor

Taig commented May 8, 2018

I'm fine with keeping my own copy of this around until 0.19 is released, so that's not an issue for me. Let me know if you want the renaming, I don't mind waiting for 0.19.

Taig added some commits May 7, 2018


      Add BlockingHttp4sServlet

4a1efa9


      IO.x instead of Sync[IO].x

3c029da


      OOP patch for a typelevel project ¯\_(ツ)_/¯

b76ad53

Taig force-pushed the Taig:develop branch from `e5debd7` to `b76ad53` May 8, 2018

rossabaker approved these changes May 8, 2018

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We could even backport the copy-and-pasted version to 0.18 if you need it now. I think it's better to move forward with the better names, so this looks good for master.

ChristopherDavenport approved these changes May 8, 2018

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If we're happy waiting, I'm happy with it. 👍

Member

rossabaker commented May 9, 2018

Test failure is related, fixed by #1836.

rossabaker merged commit `37bf4e7` into http4s:master May 9, 2018
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Taig deleted the Taig:develop branch May 9, 2018

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