HTTPS request on Lambda very slow on first request

Hi,

I am making HTTPS POST request to an API. The first request I make will take somewhere between 30-130 seconds. The subsequent request only takes 2-300 ms. This API handles millions of requests every day, so the problem does not seem to be in the API.

My simple test code:

 const https = require('https');

const acquire = (data, options) => {
  return new Promise((resolve, reject) => {
    options.headers['Content-Length'] = data.length;
    const req = https.request(options, (res) => {
      console.log("REQ compl")
      res.on('data', (data) => {
        console.log(data)
        resolve(data)
      });
    });
    req.on ('error', (error) => {
      console.log("error", error)
    })
    req.write(data);
    req.end();
  })
}

const release = (data, options) => {
  return new Promise((resolve, reject) => {
    options.headers['Content-Length'] = data.length;
    const req = https.request(options, (res) => {
      console.log("REQ compl")
      res.on('data', (data) => {
        console.log(data)
        resolve(data)
      })
    });
    req.on ('error', (error) => {
      console.log("error", error)
    })
    req.write(data);
    req.end();
  })
}

const data = `<methodCall>
  <methodName>acquire_token</methodName>
  <params>
    <param>
      <value>
        <string>KS034</string>
      </value>
    </param>
    <param>
      <value>
        <string>password</string>
      </value>
    </param>
    <param>
      <value>
        <string>secret string</string>
      </value>
    </param>
  </params>
</methodCall>`

const options = {
  hostname: 'wired.wubook.net',
  port: 443,
  path: '/xrws/',
  method: 'POST',
  headers: {
    'Content-Type': 'text/xml',
    'Connection': 'keep-alive',
    'Content-Length': 0
  }
}

exports.handler = async (event) => {
  let resa = 'aaa';
  let resb = '';
    
  await acquire(data, options).then(res => {
    xmlrpc.CustomType.call()
    res = res.toString();
    console.log("acquire complete")
    var start = res.indexOf("<string>");
    var end = res.indexOf("</string>");
    // resa = JSON.stringify(res);
    resa = res.substring(start + 8, end)
  });

  const data1 = `<methodCall>
    <methodName>release_token</methodName>
    <params>
      <param>
        <value>
          <string>${resa}</string>
        </value>
      </param>
    </params>
  </methodCall>`

  await release(data1, options).then(res => {
    resb = res;
    console.log("release complete")
  });

  const response = {
    statusCode: 200,
    body: JSON.stringify('Hello from Lambda!' + resa + resb)
  }
  return response;

};

Is there anything that can explain this behavior? I have tried the XMLRPC client for NodeJS as well; the result is the same unfortunately.

Thank you very much!

Edited by: KasperS on Jan 21, 2020 11:49 AM