Logstash over-reload

Logstash v 2.3

When specified auto-reload interval and your config file is too big (too many filters, etc.), logstash is too slow when checking if config is changed.

When checking changes is slower than reload interval, CPU is on 100% and memory usage slowly grows without limit.

No source files, tests, or entry points are named. Start by reproducing the issue with a large configuration containing many filters and an auto-reload interval, then trace the configuration-change check and reload loop. Done means checking changes no longer drives CPU to 100% or causes unbounded memory growth when checking takes longer than the reload interval.

Written by the indexing model from the issue text.