Aleph deadlock

core.clj

(ns aleph-deadlock.core
  (:require [aleph.http :as http]
            [manifold.deferred :as d]
            [taoensso.timbre :as log])
  (:import (java.net InetAddress InetSocketAddress)))

(defn handler [_]
  {:status 200
   :body "Hello, world"})

(defn start-server []
  (let [addr (InetSocketAddress.
              (InetAddress/getByName "localhost")
              9992)]
    (http/start-server #'handler {:socket-address addr})))

(def server (start-server))

(def client-pool (http/connection-pool {:keep-alive? true
                                        :connections-per-host 5}))


(defn make-request []
  (http/post "http://localhost:9992" {:headers {"Connection" "Close"} ;; this is important
                                      :pool client-pool}))

(defn make-requests [num-reqs]
  (let [req-count (atom 0)]
    (->> (repeatedly num-reqs #(make-request))
         (map #(d/chain % (fn [_] (log/infof "---> Request done: %s"
                                            (swap! req-count inc))
                            :ok)))
         doall
         (apply d/zip))))

;; for :connections-per-host = 5, the below will almost certainly block forever
;; to increase the probability of a deadlock just increase number of requests to make
@(make-requests 10)