1. An adaptive enterprise service bus (ESB) runtime system comprising: a processor operable to receive a model for an enterprise system bus (ESB), said model comprising a plurality of paths between composable units with at least one of said paths comprising a plurality of branches and said processor being further operable to build executable instantiations of said paths and said branches; a server operable to execute, during each running of said runtime system, said executable instantiations of said paths and said branches built by said processor so as to allow communication between said composable units; a monitor collecting, during executing of said executable instantiations by said server, metrics associated with said paths and said branches; and, an analyzer receiving said metrics and performing a cost-benefit analysis based on said metrics, said processor further building, at a restart of said runtime system and based on results of said cost-benefit analysis, executable instantiations of only selected ones of said paths and said branches.