private Throwable checkpoint(Throwable accumulate) {
if (logger.isDebugEnabled())
logger.debug("Checkpointing update:{}, obsolete:{}", staged.update, staged.obsolete);
if (staged.isEmpty()) return accumulate;
Set<SSTableReader> toUpdate = toUpdate();
Set<SSTableReader> fresh = copyOf(fresh());
// check the current versions of the readers we're replacing haven't somehow been replaced by
// someone else
checkNotReplaced(filterIn(toUpdate, staged.update));
// ensure any new readers are in the compacting set, since we aren't done with them yet
// and don't want anyone else messing with them
// apply atomically along with updating the live set of readers
tracker.apply(
compose(updateCompacting(emptySet(), fresh), updateLiveSet(toUpdate, staged.update)));
// log the staged changes and our newly marked readers
marked.addAll(fresh);
logged.log(staged);
// setup our tracker, and mark our prior versions replaced, also releasing our references to
// them
// we do not replace/release obsoleted readers, since we may need to restore them on rollback
accumulate = setReplaced(filterOut(toUpdate, staged.obsolete), accumulate);
accumulate = release(selfRefs(filterOut(toUpdate, staged.obsolete)), accumulate);
staged.clear();
return accumulate;
}
void log(State staged) {
update.removeAll(staged.obsolete);
update.removeAll(staged.update);
update.addAll(staged.update);
obsolete.addAll(staged.obsolete);
}