private boolean saveFirstLogIndex(final long firstLogIndex) {
        this.readLock.lock();
        try {
            checkState();
            DatabaseEntry firstLogIndexKey = new DatabaseEntry(FIRST_LOG_IDX_KEY);
            DatabaseEntry firstLogIndexValue = getKeyDatabaseEntry(firstLogIndex);
            this.confTable.put(null, firstLogIndexKey, firstLogIndexValue);
            syncIfNeed();
            return true;
        } catch (DatabaseException e) {
            LOG.error("Fail to save first log index {}.", firstLogIndex, e);
        } finally {
            this.readLock.unlock();
        }
        return false;
    }
Save the first log index into {@link BDBLogStorage#confTable} }
jraft-extension/bdb-log-storage-impl/src/main/java/com/alipay/sofa/jraft/storage/impl/BDBLogStorage.java