@Override
    public boolean releaseMaster() {
        if (masterFlag) {
            clusterMasterLock.unlock();
            masterFlag = false;
        }
        return true;
    }
The cluster select master service jdbc impl.
shenyu-admin/src/main/java/org/apache/shenyu/admin/mode/cluster/impl/jdbc/ClusterSelectMasterServiceJdbcImpl.java