http-check.js

var async = require( "async" );
var request = require( "request" );

var urls = ["http://google.com", "http://facebook.com"];

function runJobs(){
  async.eachLimit( urls, 5, function( url, cb ){
    request( url, function( err ){
      if( err ){
        console.error( "failed to get url: %s", url, err );
      }
      cb();
    });
  }, function(){
    setTimeout( runJobs, 5000 );
  });
}

runJobs();