fix a bunch of races + simpler and faster draining
fix a bunch of races + simpler and faster draining

replay/metrictank,raintank/raintank-metric,replay/metrictank,raintank/metrictank,replay/metrictank,raintank/raintank-metric,raintank/metrictank,replay/metrictank,raintank/metrictank,raintank/raintank-metric,raintank/metrictank