Skip caching of aggregation transformation output
Skip caching of aggregation transformation output

Reported in issue #185 via @dkulikovsky
Each aggregation rule caches transformations to avoid unneeded regex
matches. In the case of many rules, each rule will maintain a cache for
ever metric it sees, whether or not that metric is matched. This
manifests for some users as a memory leak

Instead, compromise by not caching the negative result, storing only
metric transformations that actually match have an output

graphite-server/carbon,kharandziuk/carbon,JeanFred/carbon,criteo-forks/carbon,benburry/carbon,krux/carbon,pu239ppy/carbon,deniszh/carbon,pratX/carbon,piotr1212/carbon,deniszh/carbon,xadjmerripen/carbon,iain-buclaw-sociomantic/carbon,obfuscurity/carbon,piotr1212/carbon,graphite-project/carbon,cbowman0/carbon,graphite-project/carbon,lyft/carbon,JeanFred/carbon,pratX/carbon,johnseekins/carbon,krux/carbon,graphite-server/carbon,johnseekins/carbon,kharandziuk/carbon,lyft/carbon,mleinart/carbon,obfuscurity/carbon,mleinart/carbon,benburry/carbon,criteo-forks/carbon,iain-buclaw-sociomantic/carbon,xadjmerripen/carbon,cbowman0/carbon,pu239ppy/carbon