http - 使用带有 core.async channel 的 http-kit 长轮询

Question

我有一些长时间运行的进程，当进程完成时，它会返回一个带有结果的 core.async channel 。

现在我想通过 HTTP-kit 使用长轮询返回该结果。不幸的是，我有点困惑这样做的正确方法是什么。

目前我有一个处理程序(连接到路由)启动处理调用并在完成时发送结果:

(defn handler
  [request]
  (let [c (process request)] ;; long running process that returns a channel
    (http/with-channel request channel
      (http/send! channel {:status 200
                           :body (<!! (go (<! c)))))
      (http/on-close channel (fn [_] (async/close! c))))))

它有效，但我不确定这是否是正确的方法。

编辑自<!!正在阻塞 我现在正在 go-loop 中尝试非阻塞变体

(defn handler
  [request]
  (let [c (process request)]
    (http/with-channel request channel
      (async/go-loop [v (<! c)]
        (http/send! channel {:status 200
                             :body v}))
      (http/on-close channel (fn [_] (async/close! c))))))

Answer 1

为什么不在 go block 中的 channel 上发送？

(http/with-channel request channel
  (go (http/send! channel (<! c))))

<!!正在阻塞 - 因此直接调用 <!! c 在您的代码中没有真正的优势在处理程序中:

(defn handler
[request]
(let [c (process request)] ;; long running process that returns a channel
{:status 200
:body (<!! c)}))

---

根据问题更新进行编辑:更新后的代码有效 - 这是一个功能齐全的命名空间，适合我:

(ns async-resp.core
  (:require [org.httpkit.server :as http]
            [clojure.core.async :as async :refer (<! >! go chan go-loop close! timeout)]))

(defn process
  [_]
  (let [ch (chan)]
    (go
      (<! (timeout 5000))
      (>! ch "TEST"))
    ch))

(defn test-handler
  [request]
  (let [c (process request)]
    (http/with-channel request channel
      (go-loop [v (<! c)]
        (http/send! channel {:status 200
                             :body v}))
      (http/on-close channel (fn [_] (close! c))))))

(defn run
  []
  (http/run-server test-handler {}))

但截至目前，我不得不手动将 tools.analyzer.jvm 依赖项添加到 project.clj - 因为我按原样使用 core.async 时遇到编译失败。

检查您是否正在运行最新的 core.async 和分析器？