Connect ETIMEDOUT to Azure App Service when calling an HTTP endpoint without specifying maxSockets

Question

I have some timeout problems when calling the HTTP [S] endpoint multiple times from node.js inside Azure application service.

Here is my code to demonstrate the problem.

const fetch = require('node-fetch');
const https = require("https");
const agent = new https.Agent();

function doWork() {
  const works = [];
  for (let i = 0; i < 50; i++) {
    const wk = fetch('https://www.microsoft.com/robots.txt', { agent })
    .then(res => res.text())
    .then(body => console.log("OK", i))
    .catch((err) => console.log("ERROR", i, err));
    works.push(wk);
  }

  return Promise.all(works);
}

doWork()
.catch((err) => {
  console.log(err);
});

When I run this application 3 or 4 times in the service of the standard mid-sized application (I launch it using Kudu, but I find this error in the standard web application). I get the following error for each request:

{ FetchError: request to https://www.microsoft.com/robots.txt failed, reason: connect ETIMEDOUT 23.206.106.109:443
    at ClientRequest.<anonymous> (D:\home\site\test\test-forge-calls\node_modules\node-fetch\lib\index.js:1393:11)
    at emitOne (events.js:96:13)
    at ClientRequest.emit (events.js:188:7)
    at TLSSocket.socketErrorListener (_http_client.js:310:9)
    at emitOne (events.js:96:13)
    at TLSSocket.emit (events.js:188:7)
    at emitErrorNT (net.js:1276:8)
    at _combinedTickCallback (internal/process/next_tick.js:74:11)
    at process._tickCallback (internal/process/next_tick.js:98:9)
  message: 'request to https://www.microsoft.com/robots.txt failed, reason: connect ETIMEDOUT 23.206.106.109:443',
  type: 'system',
  errno: 'ETIMEDOUT',
  code: 'ETIMEDOUT' }

After a few minutes (5/6) without executing the requests, the above code works again.

node-fetch (https://www.npmjs.com/package/node-fetch) request (https://www.npmjs.com/package/request). . , agent , ( ).

Microsoft Best Practices node.js keep alive agent :

var keepaliveAgent = new Agent({    
    maxSockets: 40,    
    maxFreeSockets: 10,    
    timeout: 60000,    
    keepAliveTimeout: 300000    
});

:

const agent = new https.Agent({ maxSockets: 100 });

, .

? node.js? agent maxSockets Azure?

UPDATE:

, node index 3 4 , , node, , . TIME_WAIT?