Investigate memory consumption of metrics-web
Last week, metrics-web on yatei ran out of memory quite often. The reason is probably that we're reading too much stuff from stats/ (in order to avoid parsing stuff twice) without garbage collecting aggressively enough. In particular, stats/archives-import-history and stats/bridge-stats-raw might be problematic.
The workaround was to change max memory from 4G to 8G. This fixes the problem for now, but obviously we can do better.