private void triggerLeaderSnapshot(final TestCluster cluster, final Node leader) throws InterruptedException {
        this.triggerLeaderSnapshot(cluster, leader, 1);
    }
Test rollback stateMachine with readIndex for issue 317:
https://github.com/sofastack/sofa-jraft/issues/317
jraft-extension/java-log-storage-impl/src/test/java/com/alipay/sofa/jraft/core/NodeTest.java