Created
April 7, 2019 04:00
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(ns backend.free-port | |
(:require [clojure.string :as str] | |
[clojure.java.shell :as shell] | |
[taoensso.timbre :as timbre])) | |
;; copy from https://gist.github.com/ptaoussanis/4283150 | |
;; A little utility to allow simple redeployment of Clojure web servers with zero downtime, and without the need for a proxy or load balancer. Just wrap any port-binding calls, and the utility will auto kill pre-existing servers as necessary. *nix only. Based on the blog post by Feng Shen, http://shenfeng.me/fast-restart-clojure-webapp.html | |
(defn with-free-port! | |
"Attempts to kill any current port-binding process, then repeatedly executes | |
nullary `bind-port!-fn` (which must return logical true on successful | |
binding). Returns the function's result when successful, else throws an | |
exception. *nix only. | |
This idea courtesy of Feng Shen, Ref. http://goo.gl/kEolu." | |
[port bind-port!-fn & {:keys [max-attempts sleep-ms] | |
:or {max-attempts 50 | |
sleep-ms 150}}] | |
(let [binder-pid (str/trim (:out (shell/sh "sudo" "-S" "/usr/bin/lsof" "-t" "-sTCP:LISTEN" | |
(str "-i:" port))))] | |
(when-not (str/blank? binder-pid) | |
(timbre/warn "Attempting to kill process" binder-pid "to free port" port) | |
(let [kill-resp (shell/sh "sudo" "-S" "kill" binder-pid)] | |
(when-not (= (:exit kill-resp) 0) | |
(throw (Exception. (str "Failed to kill process " binder-pid | |
" while trying to free port " port ": " | |
(:err kill-resp))))))) | |
(loop [attempt 1] | |
(when (> attempt max-attempts) | |
(throw (Exception. (str "Failed to bind to port " port " within " | |
max-attempts " attempts (" | |
(* max-attempts sleep-ms) "ms)")))) | |
(let [result (try (bind-port!-fn) (catch java.net.BindException _))] | |
(if result | |
(do (timbre/info (str "Bound to port " port " after " | |
attempt " attempt(s)")) | |
result) | |
(do (Thread/sleep sleep-ms) | |
(recur (inc attempt)))))))) | |
(comment (with-free-port! 8080 (fn [] (ring.adapter.jetty/run-jetty my-handler {:port 8080 :join? false})))) |
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