default concurrency if not provided
default concurrency if not provided

pratikmallya/rack,nelsnelson/rack,jrperritt/rack,jrperritt/rack,jarosser06/rack,jarosser06/rack,dolph/rack,pratikmallya/rack,annegentle/rack,DonNateR/rack,ryanvz/rack,brint/rack,annegentle/rack,ryanvz/rack,brint/rack,dolph/rack,nelsnelson/rack,rackspace/rack,DonNateR/rack,rackspace/rack