This commit disables the hard space limit applied by commitlogs created
to store hints. The hard limit causes problems for hints because they
use small-sized commitlogs to store hints (128MB, currently). Instead of
letting the commitlog delete the segments itself, it recreates the
commitlog every 10 seconds and manually deletes old segments after all
hints are sent out from them.
If the 128MB limit is reached, the hints manager will get stuck. A
future which puts hint into commitlog holds a shared lock, and commitlog
recreation needs to get an exclusive lock, which results in a deadlock.
No more hints will be admitted, and eventually we will start rejecting
writes with OverloadedException due to too many hints waiting to be
admitted to the commitlog.
By disabling the hard limit for hints commitlog, the old behavior is
brought back - commitlog becomes more conservative with the space used
after going over its size limit, but does not block until some of its
segments are deleted.
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