REPO-5110 readConfigAndReplace NPE on shutdown (#246)

Suppresses reading of new config if the system is shutting down.

src/main/java/org/alfresco/repo/content/MimetypeMap.java

@@ -2,7 +2,7 @@
  * #%L
  * Alfresco Data model classes
  * %%
- * Copyright (C) 2005 - 2019 Alfresco Software Limited
+ * Copyright (C) 2005 - 2020 Alfresco Software Limited
  * %%
  * This file is part of the Alfresco software. 
  * If the software was purchased under a paid Alfresco license, the terms of 
@@ -34,6 +34,7 @@ import org.alfresco.service.cmr.repository.MimetypeService;
 import org.alfresco.util.ConfigFileFinder;
 import org.alfresco.util.ConfigScheduler;
 import org.alfresco.util.PropertyCheck;
+import org.alfresco.util.ShutdownIndicator;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.tika.config.TikaConfig;
@@ -553,6 +554,11 @@ public class MimetypeMap implements MimetypeService
         this.initialAndOnErrorCronExpression = initialAndOnErrorCronExpression;
     }
 
+    public void setShutdownIndicator(ShutdownIndicator shutdownIndicator)
+    {
+        configScheduler.setShutdownIndicator(shutdownIndicator);
+    }
+
     /**
      * Initialises the map using the configuration service provided
      */

src/main/java/org/alfresco/util/ConfigScheduler.java

@@ -2,7 +2,7 @@
  * #%L
  * Alfresco Repository
  * %%
- * Copyright (C) 2005 - 2019 Alfresco Software Limited
+ * Copyright (C) 2005 - 2020 Alfresco Software Limited
  * %%
  * This file is part of the Alfresco software.
  * If the software was purchased under a paid Alfresco license, the terms of
@@ -83,11 +83,23 @@ public abstract class ConfigScheduler<Data>
     protected Data data;
     private ThreadLocal<Data> threadData = ThreadLocal.withInitial(() -> data);
 
+    private ShutdownIndicator shutdownIndicator;
+
     public ConfigScheduler(Object client)
     {
         jobName = client.getClass().getName()+"Job@"+Integer.toHexString(System.identityHashCode(client));
     }
 
+    public void setShutdownIndicator(ShutdownIndicator shutdownIndicator)
+    {
+        this.shutdownIndicator = shutdownIndicator;
+    }
+
+    private boolean shuttingDown()
+    {
+        return shutdownIndicator != null && shutdownIndicator.isShuttingDown();
+    }
+
     public abstract boolean readConfig() throws IOException;
 
     public abstract Data createData();
@@ -198,7 +210,13 @@ public abstract class ConfigScheduler<Data>
      */
     public boolean readConfigAndReplace(boolean scheduledRead)
     {
-        boolean successReadingConfig;
+        // Config replacement is not done during shutdown. We cannot even log it without generating an INFO message.
+
+        // If shutting down, we return true indicating there were not problems, as that will result in the next
+        // scheduled job taking place later where as false would switch to a more frequent retry sequence.
+        boolean successReadingConfig = true;
+        if (!shuttingDown())
+        {
             log.debug((scheduledRead ? "Scheduled" : "Unscheduled") + " config read started");
             Data data = getData();
             try
@@ -216,6 +234,7 @@ public abstract class ConfigScheduler<Data>
                 log.error("Config read failed. " + e.getMessage(), e);
             }
             setData(data);
+        }
         return successReadingConfig;
     }
 

src/main/java/org/alfresco/util/ShutdownIndicator.java

@@ -0,0 +1,69 @@
+/*
+ * #%L
+ * Alfresco Repository
+ * %%
+ * Copyright (C) 2005 - 2020 Alfresco Software Limited
+ * %%
+ * This file is part of the Alfresco software.
+ * If the software was purchased under a paid Alfresco license, the terms of
+ * the paid license agreement will prevail.  Otherwise, the software is
+ * provided under the following open source license terms:
+ *
+ * Alfresco is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Alfresco is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
+ * #L%
+ */
+package org.alfresco.util;
+
+import org.springframework.beans.BeansException;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.ApplicationContextAware;
+import org.springframework.context.ApplicationListener;
+import org.springframework.context.event.ApplicationContextEvent;
+import org.springframework.context.event.ContextClosedEvent;
+
+/**
+ * Listens to ApplicationEvents to provide a simple {@link #isShuttingDown()} method, so callers don't need to be
+ * Spring beans or listen to these events themselves. Intended for use by code that wishes to avoid ERROR log messages
+ * on shutdown.
+ *
+ * @author adavis
+ */
+public class ShutdownIndicator implements ApplicationContextAware, ApplicationListener<ApplicationContextEvent>
+{
+    private boolean shuttingDown;
+    private ApplicationContext applicationContext;
+
+    public synchronized boolean isShuttingDown()
+    {
+        return shuttingDown;
+    }
+
+    @Override
+    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException
+    {
+        this.applicationContext = applicationContext;
+    }
+
+    @Override
+    public void onApplicationEvent(ApplicationContextEvent event)
+    {
+        if (event instanceof ContextClosedEvent && event.getSource() == applicationContext)
+        {
+            synchronized (this)
+            {
+                shuttingDown = true;
+            }
+        }
+    }
+}