重新踏入網頁開發 (5) - Blocking & Non-Blocking

Blocking ＆ Non-Blocking

    Nodejs 為事件觸發的單一執行緒，不像 Apache + PHP 會自動開一個 Thread 去接每一個 Request。

    Blocking Code 示範 (程式碼另有 index.js 請參照重新踏入網頁開發 (4) - Dependency injection)

• route.js

      function start_requset_handle () {
          console.log("Start request.");
          
          // Sleep for 10 seconds
          function sleep(milliSeconds) {
              var startTime = new Date().getTime();
              while (new Date().getTime() < startTime + milliSeconds);
          }
          sleep(10000);
      }
  
      function upload_requset_handle () {
          console.log("Upload request.");
      }
  
      function requset_handler (url) {
          var handle = {};
          handle['/'] = start_requset_handle;
          handle['/start'] = start_requset_handle;
          handle['/upload'] = upload_requset_handle;
  
          if (typeof handle[url] === 'function') {
              handle[url]();
          } else {
              console.log("No request handler found for " + url);
          }
      }
  
      export function route(url) {
          requset_handler(url);
      }

• server.js

      import http from 'http'
      import url from 'url'
  
      export function serverStart(route) {
          function onRequest(request, response) {
              var path_name = url.parse(request.url).pathname;
              console.log("Request for " + path_name + " received");
              
              // Routing function
              route(path_name);
  
              response.writeHead(200, {"Content-Type": "text/plain"});
              response.write("Hello World.\n");
              response.end();
          }
          http.createServer(onRequest).listen(8888);
          console.log("Server has started...");
      }

    這裡先用 requset_handler() 這 function 去應對 2 種 url 的 request。client 端 request http://localhost:8888/start 會等 10 秒才回覆 Hello World.，request http://localhost:8888/upload 則立即回覆。因為 nodejs 為單一執行緒，如果有人先 request start, 後面即使是 request upload 也要跟著等 10 秒。

    Non-Blocking Code 示範 (程式碼另有 index.js 請參照重新踏入網頁開發 (4) - Dependency injection)

• route.js

      import { exec } from 'child_process';
  
      function start_requset_handle (response) {
          console.log("Start request.");
          var content = "empty\n";
          exec("ls -alh", function (error, stdout, stderr) {
              content = stdout;
              response.writeHead(200, {"Content-Type": "text/plain"});
              response.write(content);
              response.end();
          });
          // 放在外面會讓 server 直接回 empty
          // response.writeHead(200, {"Content-Type": "text/plain"});
          // response.write(content);
          // response.end();
      }
  
      function upload_requset_handle (response) {
          console.log("Upload request.");
          response.writeHead(200, {"Content-Type": "text/plain"});
          response.write("Uploading...\n");
          response.end();
      }
  
      function requset_handler (url, response) {
          var handle = {};
          handle['/'] = start_requset_handle;
          handle['/start'] = start_requset_handle;
          handle['/upload'] = upload_requset_handle;
  
          if (typeof handle[url] === 'function') {
              handle[url](response);
          } else {
              console.log("No request handler found for " + url);
          }
      }
  
      export function route(url, response) {
          requset_handler(url, response);
      }

• server.js

      import http from 'http'
      import url from 'url'
  
      export function serverStart(route) {
          function onRequest(request, response) {
              var path_name = url.parse(request.url).pathname;
              console.log("Request for " + path_name + " received");
              
              // Routing function
              route(path_name, response);
          }
          http.createServer(onRequest).listen(8888);
          console.log("Server has started...");
      }

    import nodejs 內建的 child_process，解決了問題。傳 response 進去是為了讓 request 處理完再做回覆。

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重新踏入網頁開發 (4) - Dependency injection

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重新踏入網頁開發 (6) - Express - 1

參考資料 :

1. https://www.nodebeginner.org/index-zh-tw.html#hello-world

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