protected Chain<PROCESSOR> getChain(ComponentSpecification chainSpec) {
        Chain<PROCESSOR> chain = getChains().getComponent(chainSpec);
        if (chain == null) {
            throw new IllegalArgumentException("No such chain: " + chainSpec);
        }
        return chain;
    }
Processes the given request with the given chain, and returns the response.

@param chain the specification of the chain to execute
@param request the request to process
@return a response
application/src/main/java/com/yahoo/application/container/ProcessingBase.java