restart-node-test.java

    /**
     *
     */
    public void testClusterStateCleanup() throws Exception {
        final int NUM_NODES = 3;

        // TODO: figure out how to manipulate the election settings so that elections occur and are quick -- took like 30 seconds?!?! And multiple elections occurred, races.
        final Settings settings = Settings.builder().put(ELECTION_MAX_TIMEOUT_SETTING.getKey(), "500ms").build();

        // Start some master nodes
        for (int i = 0; i < NUM_NODES; i++) {
           // startMasterOnlyNode(settings);
            startMasterOnlyNode();
        }
        // Wait for an election.
        ensureGreen();

        var nodeNames = internalCluster().getNodeNames();

        // Failover the master a few times, to generate new cluster state term directories in the blob store.
        for (int i = 0; i < 3; i++) {
            logger.info("~~~~stopping master node" + i);
            internalCluster().restartNode(internalCluster().getMasterName(), InternalTestCluster.EMPTY_CALLBACK);
//            internalCluster().stopCurrentMasterNode();
            // Wait for a new master to be elected.
            logger.info("~~~~waiting for green...");
            ensureGreen();
        }


        // TODO: check the blob store directories for 3 master directories
        int numTerms = countTermDirectories();
        assert numTerms >= 2 : "expected to find at least three term directories, but only found: " + numTerms;

        // The {@link co.elastic.elasticsearch.stateless.cluster.coordination.StatelessClusterStateCleanupService#CLUSTER_STATE_CLEANUP_DELAY_MINUTES}
        // value defaults to 5 minutes. We will want this to happen more quickly for testing purposes, but enough time to check first that the expected term directories are present
        for (int i = 0; i < internalCluster().size(); ++i) {
            // Set 1-millisecond delay before cleaning up old cluster state.
            internalCluster().getInstance(StatelessClusterStateCleanupService.class, nodeNames[i]).setClusterStateCleanupDelayMinutesForTest(new TimeValue(1, TimeUnit.SECONDS));
        }

        assertBusy(() -> {
            int terms = countTermDirectories();
            assert terms == 1 : "found more than one term directory: " + terms;
        });
    }
}