Isolated test case for https://github.com/aws/aws-sdk-js/issues/445.

index.js

var concurrency = 100;

var http = require('http');
http.globalAgent.maxSockets = concurrency;

var AWS = require('aws-sdk');
var s3 = new AWS.S3();

for (var i = 0; i < concurrency; i++) {
    s3.listBuckets(callback);
}

function callback(err) { if (err) throw err; }

package.json

{
  "name": "",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "aws-sdk": "^2.0.31"
  }
}

Ran on node v0.10.33 / c3.large / ubuntu-trusty-14.04-amd64-server-20140927 (ami-98aa1cf0).

@1.0.0 /usr/local/src/metadata-creds
└─┬ aws-sdk@2.0.31
  ├─┬ xml2js@0.2.6
  │ └── sax@0.4.2
  └── xmlbuilder@0.4.2

Receive the following output when concurrency is set to 100 or above:

/usr/local/src/metadata-creds/node_modules/aws-sdk/lib/request.js:32
          throw err;
                ^
CredentialsError: Missing credentials in config
    at createHangUpError (http.js:1476:15)
    at Socket.socketOnEnd [as onend] (http.js:1572:23)
    at Socket.g (events.js:180:16)
    at Socket.emit (events.js:117:20)
    at _stream_readable.js:943:16
    at process._tickDomainCallback (node.js:463:13)