Avoid test race when starting initial join

Author: jasontedor

core/src/test/java/org/elasticsearch/discovery/single/SingleNodeDiscoveryTests.java

@@ -21,17 +21,22 @@
 
 import org.apache.lucene.util.IOUtils;
 import org.elasticsearch.Version;
+import org.elasticsearch.cluster.ClusterState;
+import org.elasticsearch.cluster.ClusterStateObserver;
 import org.elasticsearch.cluster.node.DiscoveryNode;
 import org.elasticsearch.cluster.node.DiscoveryNodes;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.common.unit.TimeValue;
+import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.test.ESTestCase;
 import org.elasticsearch.test.transport.MockTransportService;
 import org.elasticsearch.threadpool.TestThreadPool;
 import org.elasticsearch.threadpool.ThreadPool;
 
 import java.io.Closeable;
 import java.util.Stack;
+import java.util.concurrent.CountDownLatch;
 
 import static org.elasticsearch.test.ClusterServiceUtils.createClusterService;
 import static org.hamcrest.Matchers.equalTo;
@@ -54,6 +59,34 @@ public void testInitialJoin() throws Exception {
             final SingleNodeDiscovery discovery =
                     new SingleNodeDiscovery(Settings.EMPTY, clusterService);
             discovery.startInitialJoin();
+
+            // we are racing against the initial join which is asynchronous so we use an observer
+            final ClusterState state = clusterService.state();
+            final ThreadContext threadContext = threadPool.getThreadContext();
+            final ClusterStateObserver observer =
+                    new ClusterStateObserver(state, clusterService, null, logger, threadContext);
+            if (state.nodes().getMasterNodeId() == null) {
+                final CountDownLatch latch = new CountDownLatch(1);
+                observer.waitForNextChange(new ClusterStateObserver.Listener() {
+                    @Override
+                    public void onNewClusterState(ClusterState state) {
+                        latch.countDown();
+                    }
+
+                    @Override
+                    public void onClusterServiceClose() {
+                        latch.countDown();
+                    }
+
+                    @Override
+                    public void onTimeout(TimeValue timeout) {
+                        assert false;
+                    }
+                }, s -> s.nodes().getMasterNodeId() != null);
+
+                latch.await();
+            }
+
             final DiscoveryNodes nodes = clusterService.state().nodes();
             assertThat(nodes.getSize(), equalTo(1));
             assertThat(nodes.getMasterNode().getId(), equalTo(node.getId()));