Run the Kitura router on a DispatchQueue instead of an ELT #78
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| @@ -23,7 +23,7 @@ import Foundation | |||
| public class HTTPServerResponse: ServerResponse { | |||
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| /// The channel handler context on which an HTTP response should be written | |||
| private weak var ctx: ChannelHandlerContext? | |||
| private weak var channel: Channel? | |||
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| if let delegate = weakSelf.server.delegate { | ||
| Monitor.delegate?.started(request: weakSelf.serverRequest, response: weakSelf.serverResponse) | ||
| delegate.handle(request: weakSelf.serverRequest, response: weakSelf.serverResponse) | ||
| } //TODO: failure path |
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Can we sort out this failure TODO now?
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Yeah, I think we can use the HTTPDummyServerDelegate here. We use that if no delegate is registered.
| delegate.handle(request: serverRequest, response: serverResponse) | ||
| } //TODO: failure path | ||
| DispatchQueue.global().async { [weak self] in | ||
| guard let weakSelf = self else { fatalError("No HTTPHandler to proceed with the response.") } |
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Is fatalError() essential or could we carry on?
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Right, we don't need a fatalError there. I have replaced it with a Log.error. I think there's a lot of other places that need this change. Will do a cleanup PR soon.
| } | ||
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| } | ||
| //func testBadRequestFollowingGoodRequest() { |
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We don't need to comment out the code of the test, just the entry in the test array.
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I think that doesn't work on macOS. I think Xcode doesn't pick the tests from the array, it runs all tests found in a file. I may be wrong - just trying a travis CI run.
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It failed: https://travis-ci.org/IBM-Swift/Kitura-NIO/jobs/419978530
Reverting back.
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I'm sorry, you were right!
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@ianpartridge Thanks for the review! I've addressed all of your comments. |
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Currently, the Kitura router that eventually invokes the endpoint handlers runs on the event loop threads. This is bad design primarily because the handlers may invoke blocking code which will end up blocking the event loop threads, reducing their availability to handle newer HTTP requests.
This pull request proposes moving the Kitura router invocation to a DispatchQueue, effectively freeing up the event loop thread which was scheduled to handle the related HTTP request. We move back to the event loop while writing the response -
HTTPServerResponse.end(). Error handling (error responses) is done on the event loop. To write responses we useChannels, instead ofChannelHandlerContexts, owing to the thread-safety provided by them.