From 5bd198043850ec64c68e9bf0659543b9aebd90b6 Mon Sep 17 00:00:00 2001
From: Justin Bertram <jbertram@apache.org>
Date: Wed, 15 Feb 2017 09:19:30 -0600
Subject: [PATCH] ARTEMIS-978 replicating live restarts as backup

In a cluster of replicated live/backup pairs if a backup crashes and
then its live crashes the cluster will retain the topology information
of the live such that when the live server restarts it will check the
cluster to see if its nodeID is present (which it will be) and then it
will activate as a backup rather than a live. To prevent this situation
an additional check is necessary to see if the server with the matching
nodeID is actually active or not which is done by attempting to make a
connection to it.
---
 .../impl/SharedNothingLiveActivation.java     | 29 ++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/artemis-server/src/main/java/org/apache/activemq/artemis/core/server/impl/SharedNothingLiveActivation.java b/artemis-server/src/main/java/org/apache/activemq/artemis/core/server/impl/SharedNothingLiveActivation.java
index ce0563828e..b36326c0a1 100644
--- a/artemis-server/src/main/java/org/apache/activemq/artemis/core/server/impl/SharedNothingLiveActivation.java
+++ b/artemis-server/src/main/java/org/apache/activemq/artemis/core/server/impl/SharedNothingLiveActivation.java
@@ -29,7 +29,10 @@ import org.apache.activemq.artemis.api.core.Pair;
 import org.apache.activemq.artemis.api.core.SimpleString;
 import org.apache.activemq.artemis.api.core.TransportConfiguration;
 import org.apache.activemq.artemis.api.core.client.ActiveMQClient;
+import org.apache.activemq.artemis.api.core.client.ClientSession;
+import org.apache.activemq.artemis.api.core.client.ClientSessionFactory;
 import org.apache.activemq.artemis.api.core.client.ClusterTopologyListener;
+import org.apache.activemq.artemis.api.core.client.ServerLocator;
 import org.apache.activemq.artemis.api.core.client.TopologyMember;
 import org.apache.activemq.artemis.core.client.impl.ClientSessionFactoryInternal;
 import org.apache.activemq.artemis.core.client.impl.ServerLocatorInternal;
@@ -402,7 +405,7 @@ public class SharedNothingLiveActivation extends LiveActivation {
       @Override
       public void nodeUP(TopologyMember topologyMember, boolean last) {
          boolean isOurNodeId = nodeId != null && nodeId.toString().equals(topologyMember.getNodeId());
-         if (isOurNodeId) {
+         if (isOurNodeId && isActive(topologyMember.getLive())) {
             isNodePresent = true;
          }
          if (isOurNodeId || last) {
@@ -410,6 +413,30 @@ public class SharedNothingLiveActivation extends LiveActivation {
          }
       }
 
+      /**
+       * In a cluster of replicated live/backup pairs if a backup crashes and then its live crashes the cluster will
+       * retain the topology information of the live such that when the live server restarts it will check the
+       * cluster to see if its nodeID is present (which it will be) and then it will activate as a backup rather than
+       * a live. To prevent this situation an additional check is necessary to see if the server with the matching
+       * nodeID is actually active or not which is done by attempting to make a connection to it.
+       *
+       * @param transportConfiguration
+       * @return
+       */
+      private boolean isActive(TransportConfiguration transportConfiguration) {
+         boolean result = false;
+
+         try (ServerLocator serverLocator = ActiveMQClient.createServerLocator(false, transportConfiguration);
+            ClientSessionFactory clientSessionFactory = serverLocator.createSessionFactory();
+            ClientSession clientSession = clientSessionFactory.createSession();) {
+            result = true;
+         } catch (Exception e) {
+            // ignore
+         }
+
+         return result;
+      }
+
       @Override
       public void nodeDown(long eventUID, String nodeID) {
          // no-op