@Override
        public synchronized void addFinishHook(final Runnable r) {
            if (this.hooks == null) {
                this.hooks = new CopyOnWriteArrayList<>();
            }
            this.hooks.add(r);
        }
Log Storage implementation based on rocksdb and segment files.

@author boyan(boyan@antfin.com)
jraft-core/src/main/java/com/alipay/sofa/jraft/storage/log/RocksDBSegmentLogStorage.java