Local node is discovered when cluster fails

server/src/main/java/org/elasticsearch/cluster/coordination/Coordinator.java

@@ -82,6 +82,7 @@
 import java.util.function.Consumer;
 import java.util.function.Supplier;
 import java.util.stream.Collectors;
+import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
 
 import static org.elasticsearch.cluster.coordination.NoMasterBlockService.NO_MASTER_BLOCK_ID;
@@ -189,7 +190,8 @@ public Coordinator(String nodeName, Settings settings, ClusterSettings clusterSe
 
     private ClusterFormationState getClusterFormationState() {
         return new ClusterFormationState(settings, getStateForMasterService(), peerFinder.getLastResolvedAddresses(),
-            StreamSupport.stream(peerFinder.getFoundPeers().spliterator(), false).collect(Collectors.toList()), getCurrentTerm());
+            Stream.concat(Stream.of(getLocalNode()), StreamSupport.stream(peerFinder.getFoundPeers().spliterator(), false))
+                .collect(Collectors.toList()), getCurrentTerm());
     }
 
     private void onLeaderFailure(Exception e) {

server/src/test/java/org/elasticsearch/cluster/coordination/CoordinatorTests.java

@@ -23,6 +23,7 @@
 import org.apache.logging.log4j.Level;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.apache.logging.log4j.core.LogEvent;
 import org.apache.logging.log4j.message.ParameterizedMessage;
 import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.Version;
@@ -58,6 +59,7 @@
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.logging.Loggers;
+import org.elasticsearch.common.regex.Regex;
 import org.elasticsearch.common.settings.ClusterSettings;
 import org.elasticsearch.common.settings.Setting;
 import org.elasticsearch.common.settings.Settings;
@@ -1257,6 +1259,79 @@ public void testClusterRecoversAfterExceptionDuringSerialization() {
         }
     }
 
+    public void testLogsWarningPeriodicallyIfClusterNotFormed() {
+        final long warningDelayMillis;
+        final Settings settings;
+        if (randomBoolean()) {
+            settings = Settings.EMPTY;
+            warningDelayMillis = ClusterFormationFailureHelper.DISCOVERY_CLUSTER_FORMATION_WARNING_TIMEOUT_SETTING.get(settings).millis();
+        } else {
+            warningDelayMillis = randomLongBetween(1, 100000);
+            settings = Settings.builder()
+                .put(ClusterFormationFailureHelper.DISCOVERY_CLUSTER_FORMATION_WARNING_TIMEOUT_SETTING.getKey(), warningDelayMillis + "ms")
+                .build();
+        }
+        logger.info("--> emitting warnings every [{}ms]", warningDelayMillis);
+
+        final Cluster cluster = new Cluster(3, true, settings);
+        cluster.runRandomly();
+        cluster.stabilise();
+
+        logger.info("--> disconnecting all nodes");
+
+        for (final ClusterNode clusterNode : cluster.clusterNodes) {
+            clusterNode.disconnect();
+        }
+
+        cluster.runFor(defaultMillis(LEADER_CHECK_INTERVAL_SETTING) + defaultMillis(LEADER_CHECK_TIMEOUT_SETTING),
+            "waiting for leader failure");
+
+        for (int i = scaledRandomIntBetween(1, 10); i >= 0; i--) {
+            final MockLogAppender mockLogAppender;
+            try {
+                mockLogAppender = new MockLogAppender();
+            } catch (IllegalAccessException e) {
+                throw new AssertionError(e);
+            }
+
+            try {
+                Loggers.addAppender(LogManager.getLogger(ClusterFormationFailureHelper.class), mockLogAppender);
+                mockLogAppender.start();
+                mockLogAppender.addExpectation(new MockLogAppender.LoggingExpectation() {
+                    final Set<DiscoveryNode> nodesLogged = new HashSet<>();
+
+                    @Override
+                    public void match(LogEvent event) {
+                        final String message = event.getMessage().getFormattedMessage();
+                        assertThat(message,
+                            startsWith("master not discovered or elected yet, an election requires at least 2 nodes with ids from ["));
+
+                        final List<ClusterNode> matchingNodes = cluster.clusterNodes.stream()
+                            .filter(n -> event.getContextData().<String>getValue(NODE_ID_LOG_CONTEXT_KEY)
+                                .equals(getNodeIdForLogContext(n.getLocalNode()))).collect(Collectors.toList());
+                        assertThat(matchingNodes, hasSize(1));
+
+                        assertTrue(Regex.simpleMatch("*have discovered *" + matchingNodes.get(0).toString() + "*discovery will continue*",
+                            message));
+
+                        nodesLogged.add(matchingNodes.get(0).getLocalNode());
+                    }
+
+                    @Override
+                    public void assertMatched() {
+                        assertThat(nodesLogged + " vs " + cluster.clusterNodes, nodesLogged,
+                            equalTo(cluster.clusterNodes.stream().map(ClusterNode::getLocalNode).collect(Collectors.toSet())));
+                    }
+                });
+                cluster.runFor(warningDelayMillis, "waiting for warning to be emitted");
+                mockLogAppender.assertAllExpectationsMatched();
+            } finally {
+                mockLogAppender.stop();
+                Loggers.removeAppender(LogManager.getLogger(ClusterFormationFailureHelper.class), mockLogAppender);
+            }
+        }
+    }
+
     private static long defaultMillis(Setting<TimeValue> setting) {
         return setting.get(Settings.EMPTY).millis() + Cluster.DEFAULT_DELAY_VARIABILITY;
     }
@@ -2182,12 +2257,18 @@ private List<TransportAddress> provideSeedHosts(HostsResolver ignored) {
         }
     }
 
+    private static final String NODE_ID_LOG_CONTEXT_KEY = "nodeId";
+
+    private static String getNodeIdForLogContext(DiscoveryNode node) {
+        return "{" + node.getId() + "}{" + node.getEphemeralId() + "}";
+    }
+
     public static Runnable onNodeLog(DiscoveryNode node, Runnable runnable) {
-        final String nodeId = "{" + node.getId() + "}{" + node.getEphemeralId() + "}";
+        final String nodeId = getNodeIdForLogContext(node);
         return new Runnable() {
             @Override
             public void run() {
-                try (CloseableThreadContext.Instance ignored = CloseableThreadContext.put("nodeId", nodeId)) {
+                try (CloseableThreadContext.Instance ignored = CloseableThreadContext.put(NODE_ID_LOG_CONTEXT_KEY, nodeId)) {
                     runnable.run();
                 }
             }