SONAR-7436 System Info must not fail if the monitored process is not up

36 files changed, 430 insertions, 119 deletions

diff --git a/server/sonar-ce/src/main/java/org/sonar/ce/container/ComputeEngineContainerImpl.java b/server/sonar-ce/src/main/java/org/sonar/ce/container/ComputeEngineContainerImpl.java
index be0bda6e858..cee129ecb32 100644
--- a/server/sonar-ce/src/main/java/org/sonar/ce/container/ComputeEngineContainerImpl.java
+++ b/server/sonar-ce/src/main/java/org/sonar/ce/container/ComputeEngineContainerImpl.java
@@ -108,7 +108,7 @@ import org.sonar.server.platform.ServerImpl;
 import org.sonar.server.platform.ServerLifecycleNotifier;
 import org.sonar.server.platform.ServerLogging;
 import org.sonar.server.platform.TempFolderProvider;
-import org.sonar.server.platform.monitoring.JmxConnectorProvider;
+import org.sonar.server.platform.monitoring.JmxConnectionFactoryProvider;
 import org.sonar.server.plugins.InstalledPluginReferentialFactory;
 import org.sonar.server.plugins.ServerExtensionInstaller;
 import org.sonar.server.properties.ProjectSettingsFactory;
@@ -139,7 +139,7 @@ public class ComputeEngineContainerImpl implements ComputeEngineContainer {
   private static final Object[] LEVEL_1_COMPONENTS = new Object[] {
     ComputeEngineSettings.class,
     new SonarQubeVersionProvider(),
-    new JmxConnectorProvider(),
+    new JmxConnectionFactoryProvider(),
     ServerImpl.class,
     UuidFactoryImpl.INSTANCE,
     // no EmbeddedDatabaseFactory.class, creating H2 DB if responsibility of WebServer
diff --git a/server/sonar-process-monitor/src/main/java/org/sonar/process/monitor/JavaProcessLauncher.java b/server/sonar-process-monitor/src/main/java/org/sonar/process/monitor/JavaProcessLauncher.java
index c586d7c9df0..07556a80e5f 100644
--- a/server/sonar-process-monitor/src/main/java/org/sonar/process/monitor/JavaProcessLauncher.java
+++ b/server/sonar-process-monitor/src/main/java/org/sonar/process/monitor/JavaProcessLauncher.java
@@ -38,7 +38,7 @@ import static org.sonar.process.ProcessEntryPoint.PROPERTY_PROCESS_KEY;
 import static org.sonar.process.ProcessEntryPoint.PROPERTY_SHARED_PATH;
 import static org.sonar.process.ProcessEntryPoint.PROPERTY_TERMINATION_TIMEOUT;
 
-class JavaProcessLauncher implements AutoCloseable {
+class JavaProcessLauncher {
 
   private final Timeouts timeouts;
   private final File tempDir;
@@ -50,7 +50,6 @@ class JavaProcessLauncher implements AutoCloseable {
     this.allProcessesCommands = new AllProcessesCommands(tempDir);
   }
 
-  @Override
   public void close() {
     allProcessesCommands.close();
   }
diff --git a/server/sonar-process/pom.xml b/server/sonar-process/pom.xml
index df90101c3c0..3bd9cfc33d7 100644
--- a/server/sonar-process/pom.xml
+++ b/server/sonar-process/pom.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
   <modelVersion>4.0.0</modelVersion>
   <parent>
     <groupId>org.sonarsource.sonarqube</groupId>
diff --git a/server/sonar-process/src/main/java/org/sonar/process/jmx/JmxConnection.java b/server/sonar-process/src/main/java/org/sonar/process/jmx/JmxConnection.java
index 378c135af03..4c2eaca5452 100644
--- a/server/sonar-process/src/main/java/org/sonar/process/jmx/JmxConnection.java
+++ b/server/sonar-process/src/main/java/org/sonar/process/jmx/JmxConnection.java
@@ -24,14 +24,16 @@ import java.lang.management.ManagementFactory;
 import java.lang.management.MemoryMXBean;
 import java.lang.management.MemoryUsage;
 import java.lang.management.ThreadMXBean;
-import java.util.SortedMap;
-import java.util.TreeMap;
+import java.util.LinkedHashMap;
+import java.util.Map;
 import javax.annotation.CheckForNull;
 import javax.management.JMX;
 import javax.management.MBeanServerConnection;
 import javax.management.ObjectName;
 import javax.management.remote.JMXConnector;
 
+import static java.lang.String.format;
+
 public class JmxConnection implements AutoCloseable {
 
   private static final long MEGABYTE = 1024L * 1024L;
@@ -55,12 +57,12 @@ public class JmxConnection implements AutoCloseable {
       }
       return JMX.newMBeanProxy(connection, new ObjectName(mBeanName), mBeanInterfaceClass);
     } catch (Exception e) {
-      throw new IllegalStateException("Fail to connect to MBean " + mBeanName, e);
+      throw new IllegalStateException(format("Fail to connect to MBean [%s]", mBeanName), e);
     }
   }
 
-  public SortedMap<String, Object> getSystemState() {
-    SortedMap<String, Object> props = new TreeMap<>();
+  public Map<String, Object> getSystemState() {
+    Map<String, Object> props = new LinkedHashMap<>();
     MemoryMXBean memory = getMBean(ManagementFactory.MEMORY_MXBEAN_NAME, MemoryMXBean.class);
     MemoryUsage heap = memory.getHeapMemoryUsage();
     props.put("Heap Committed (MB)", toMegaBytes(heap.getCommitted()));
diff --git a/server/sonar-process/src/main/java/org/sonar/process/jmx/JmxConnectionFactory.java b/server/sonar-process/src/main/java/org/sonar/process/jmx/JmxConnectionFactory.java
index ca906b9540d..29383cc211e 100644
--- a/server/sonar-process/src/main/java/org/sonar/process/jmx/JmxConnectionFactory.java
+++ b/server/sonar-process/src/main/java/org/sonar/process/jmx/JmxConnectionFactory.java
@@ -20,6 +20,7 @@
 package org.sonar.process.jmx;
 
 import java.io.File;
+import javax.annotation.CheckForNull;
 import javax.annotation.concurrent.Immutable;
 import javax.management.remote.JMXConnector;
 import javax.management.remote.JMXConnectorFactory;
@@ -44,14 +45,23 @@ public class JmxConnectionFactory {
     this.ipcSharedDir = props.nonNullValueAsFile(ProcessEntryPoint.PROPERTY_SHARED_PATH);
   }
 
+  @CheckForNull
   public JmxConnection create(ProcessId processId) {
     try (DefaultProcessCommands commands = DefaultProcessCommands.secondary(ipcSharedDir, processId.getIpcIndex())) {
-      String url = commands.getJmxUrl();
-      JMXConnector jmxConnector = JMXConnectorFactory.newJMXConnector(new JMXServiceURL(url), null);
-      jmxConnector.connect();
-      return new JmxConnection(jmxConnector);
+      if (commands.isUp()) {
+        String url = commands.getJmxUrl();
+        JMXConnector jmxConnector = JMXConnectorFactory.newJMXConnector(new JMXServiceURL(url), null);
+        jmxConnector.connect();
+        return new JmxConnection(jmxConnector);
+      }
+      return null;
     } catch (Exception e) {
       throw new IllegalStateException("Can not connect to process " + processId, e);
     }
   }
+
+  // visible for testing
+  File getIpcSharedDir() {
+    return ipcSharedDir;
+  }
 }
diff --git a/server/sonar-process/src/test/java/org/sonar/process/jmx/JmxConnectionFactoryTest.java b/server/sonar-process/src/test/java/org/sonar/process/jmx/JmxConnectionFactoryTest.java
new file mode 100644
index 00000000000..4709acb83d3
--- /dev/null
+++ b/server/sonar-process/src/test/java/org/sonar/process/jmx/JmxConnectionFactoryTest.java
@@ -0,0 +1,91 @@
+/*
+ * SonarQube
+ * Copyright (C) 2009-2016 SonarSource SA
+ * mailto:contact AT sonarsource DOT com
+ *
+ * This program 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.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+package org.sonar.process.jmx;
+
+import java.io.File;
+import java.util.Properties;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.junit.rules.TemporaryFolder;
+import org.sonar.process.DefaultProcessCommands;
+import org.sonar.process.ProcessId;
+import org.sonar.process.Props;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class JmxConnectionFactoryTest {
+
+  @Rule
+  public TemporaryFolder temp = new TemporaryFolder();
+
+  @Rule
+  public ExpectedException expectedException = ExpectedException.none();
+
+  @Rule
+  public JmxTestServer jmxServer = new JmxTestServer();
+
+  @Test
+  public void create_returns_null_if_process_is_down() throws Exception {
+    File ipcSharedDir = temp.newFolder();
+    JmxConnectionFactory underTest = new JmxConnectionFactory(ipcSharedDir);
+
+    JmxConnection connection = underTest.create(ProcessId.COMPUTE_ENGINE);
+
+    assertThat(connection).isNull();
+  }
+
+  @Test
+  public void create_connection_if_process_is_up() throws Exception {
+    File ipcSharedDir = temp.newFolder();
+    try (DefaultProcessCommands processCommands = DefaultProcessCommands.secondary(ipcSharedDir, ProcessId.COMPUTE_ENGINE.getIpcIndex())) {
+      processCommands.setUp();
+      processCommands.setJmxUrl(jmxServer.getAddress().toString());
+    }
+
+    JmxConnection connection = new JmxConnectionFactory(ipcSharedDir).create(ProcessId.COMPUTE_ENGINE);
+    assertThat(connection).isNotNull();
+  }
+
+  @Test
+  public void create_throws_ISE_if_fails_to_connect_to_process() throws Exception {
+    File ipcSharedDir = temp.newFolder();
+    try (DefaultProcessCommands processCommands = DefaultProcessCommands.secondary(ipcSharedDir, ProcessId.COMPUTE_ENGINE.getIpcIndex())) {
+      // process is up but does not have any JMX URL
+      processCommands.setUp();
+    }
+
+    expectedException.expect(IllegalStateException.class);
+    expectedException.expectMessage("Can not connect to process " + ProcessId.COMPUTE_ENGINE.toString());
+    new JmxConnectionFactory(ipcSharedDir).create(ProcessId.COMPUTE_ENGINE);
+  }
+
+  @Test
+  public void load_ipc_shared_dir_from_props() throws Exception {
+    File ipcSharedDir = temp.newFolder();
+    Properties props = new Properties();
+    props.setProperty("process.sharedDir", ipcSharedDir.getAbsolutePath());
+
+    JmxConnectionFactory underTest = new JmxConnectionFactory(new Props(props));
+
+    assertThat(underTest.getIpcSharedDir().getCanonicalPath()).isEqualTo(ipcSharedDir.getCanonicalPath());
+  }
+
+}
diff --git a/server/sonar-process/src/test/java/org/sonar/process/jmx/JmxConnectionTest.java b/server/sonar-process/src/test/java/org/sonar/process/jmx/JmxConnectionTest.java
index c8aa351524d..efb7f83701f 100644
--- a/server/sonar-process/src/test/java/org/sonar/process/jmx/JmxConnectionTest.java
+++ b/server/sonar-process/src/test/java/org/sonar/process/jmx/JmxConnectionTest.java
@@ -19,12 +19,46 @@
  */
 package org.sonar.process.jmx;
 
+import java.lang.management.ManagementFactory;
+import java.lang.management.RuntimeMXBean;
+import java.util.Map;
+import javax.management.ObjectName;
+import javax.management.remote.JMXConnector;
+import javax.management.remote.JMXConnectorFactory;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
 public class JmxConnectionTest {
 
+  private static final String CUSTOM_OBJECT_NAME = "Test:name=test";
+
+  @Rule
+  public ExpectedException expectedException = ExpectedException.none();
+
+  @Rule
+  public JmxTestServer jmxServer = new JmxTestServer();
+
+  JmxConnection underTest;
+
+  @Before
+  public void setUp() throws Exception {
+    jmxServer.getMBeanServer().registerMBean(new Fake(), new ObjectName(CUSTOM_OBJECT_NAME));
+    JMXConnector jmxConnector = JMXConnectorFactory.newJMXConnector(jmxServer.getAddress(), null);
+    jmxConnector.connect();
+    underTest = new JmxConnection(jmxConnector);
+  }
+
+  @After
+  public void tearDown() throws Exception {
+    underTest.close();
+    jmxServer.getMBeanServer().unregisterMBean(new ObjectName(CUSTOM_OBJECT_NAME));
+  }
+
   @Test
   public void toMegaBytes() {
     assertThat(JmxConnection.toMegaBytes(-1)).isNull();
@@ -33,4 +67,32 @@ public class JmxConnectionTest {
     assertThat(JmxConnection.toMegaBytes(500_000L)).isEqualTo(0L);
     assertThat(JmxConnection.toMegaBytes(500_000_000L)).isEqualTo(476L);
   }
+
+  @Test
+  public void get_platform_mbean() throws Exception {
+    RuntimeMXBean runtimeMBean = underTest.getMBean(ManagementFactory.RUNTIME_MXBEAN_NAME, RuntimeMXBean.class);
+
+    assertThat(runtimeMBean).isNotNull();
+  }
+
+  @Test
+  public void get_custom_mbean() throws Exception {
+    FakeMBean mbean = underTest.getMBean(CUSTOM_OBJECT_NAME, FakeMBean.class);
+
+    assertThat(mbean).isNotNull();
+  }
+
+  @Test
+  public void getMBean_fails_if_does_not_exist() throws Exception {
+    expectedException.expect(IllegalStateException.class);
+    expectedException.expectMessage("Fail to connect to MBean [unknown]");
+    underTest.getMBean("unknown", FakeMBean.class);
+  }
+
+  @Test
+  public void getSystemState() throws Exception {
+    Map<String, Object> state = underTest.getSystemState();
+    assertThat(state).containsKey("Heap Max (MB)");
+    assertThat((int) state.get("Thread Count")).isGreaterThan(0);
+  }
 }
diff --git a/server/sonar-process/src/test/java/org/sonar/process/jmx/JmxTestServer.java b/server/sonar-process/src/test/java/org/sonar/process/jmx/JmxTestServer.java
new file mode 100644
index 00000000000..9ffe8413bef
--- /dev/null
+++ b/server/sonar-process/src/test/java/org/sonar/process/jmx/JmxTestServer.java
@@ -0,0 +1,71 @@
+/*
+ * SonarQube
+ * Copyright (C) 2009-2016 SonarSource SA
+ * mailto:contact AT sonarsource DOT com
+ *
+ * This program 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.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+package org.sonar.process.jmx;
+
+import com.google.common.base.Throwables;
+import java.io.IOException;
+import java.lang.management.ManagementFactory;
+import java.rmi.registry.LocateRegistry;
+import java.util.HashMap;
+import javax.management.MBeanServer;
+import javax.management.remote.JMXConnectorServer;
+import javax.management.remote.JMXConnectorServerFactory;
+import javax.management.remote.JMXServiceURL;
+import org.junit.rules.ExternalResource;
+import org.sonar.process.NetworkUtils;
+
+public class JmxTestServer extends ExternalResource {
+
+  private final int jmxPort = NetworkUtils.freePort();
+  private JMXConnectorServer jmxServer;
+
+  @Override
+  protected void before() throws Throwable {
+    LocateRegistry.createRegistry(jmxPort);
+    JMXServiceURL serviceUrl = new JMXServiceURL("service:jmx:rmi://localhost:" + jmxPort + "/jndi/rmi://localhost:" + jmxPort + "/jmxrmi");
+    MBeanServer mbeanServer = ManagementFactory.getPlatformMBeanServer();
+    jmxServer = JMXConnectorServerFactory.newJMXConnectorServer(serviceUrl, new HashMap<String, Object>(), mbeanServer);
+    jmxServer.start();
+
+  }
+
+  @Override
+  protected void after() {
+    if (jmxServer != null) {
+      try {
+        jmxServer.stop();
+      } catch (IOException e) {
+        throw Throwables.propagate(e);
+      }
+    }
+  }
+
+  public int getPort() {
+    return jmxPort;
+  }
+
+  public MBeanServer getMBeanServer() {
+    return jmxServer.getMBeanServer();
+  }
+
+  public JMXServiceURL getAddress() {
+    return jmxServer.getAddress();
+  }
+}
diff --git a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/CeDatabaseMonitor.java b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/CeDatabaseMonitor.java
index 1b6b548e379..052d3ff5634 100644
--- a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/CeDatabaseMonitor.java
+++ b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/CeDatabaseMonitor.java
@@ -19,7 +19,9 @@
  */
 package org.sonar.server.platform.monitoring;
 
+import com.google.common.base.Optional;
 import java.util.LinkedHashMap;
+import java.util.Map;
 import org.sonar.process.ProcessId;
 import org.sonar.process.jmx.CeDatabaseMBean;
 import org.sonar.process.jmx.JmxConnection;
@@ -27,6 +29,8 @@ import org.sonar.process.jmx.JmxConnectionFactory;
 
 public class CeDatabaseMonitor implements Monitor {
 
+  private static final int NUMBER_OF_ATTRIBUTES = 9;
+
   private final JmxConnectionFactory jmxConnectionFactory;
 
   public CeDatabaseMonitor(JmxConnectionFactory jmxConnectionFactory) {
@@ -35,13 +39,16 @@ public class CeDatabaseMonitor implements Monitor {
 
   @Override
   public String name() {
-    return "Compute Engine Database";
+    return "Compute Engine Database Connection";
   }
 
   @Override
-  public LinkedHashMap<String, Object> attributes() {
+  public Optional<Map<String, Object>> attributes() {
     try (JmxConnection connection = jmxConnectionFactory.create(ProcessId.COMPUTE_ENGINE)) {
-      LinkedHashMap<String, Object> result = new LinkedHashMap<>();
+      if (connection == null) {
+        return Optional.absent();
+      }
+      Map<String, Object> result = new LinkedHashMap<>(NUMBER_OF_ATTRIBUTES);
       CeDatabaseMBean mbean = connection.getMBean(CeDatabaseMBean.OBJECT_NAME, CeDatabaseMBean.class);
       result.put("Pool Initial Size", mbean.getPoolInitialSize());
       result.put("Pool Active Connections", mbean.getPoolActiveConnections());
@@ -52,7 +59,7 @@ public class CeDatabaseMonitor implements Monitor {
       result.put("Pool Max Wait (ms)", mbean.getPoolMaxWaitMillis());
       result.put("Pool Remove Abandoned", mbean.getPoolRemoveAbandoned());
       result.put("Pool Remove Abandoned Timeout (sec)", mbean.getPoolRemoveAbandonedTimeoutSeconds());
-      return result;
+      return Optional.of(result);
     }
   }
 }
diff --git a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/CeStateMonitor.java b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/CeStateMonitor.java
index 2c834fe20b7..d920607edb6 100644
--- a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/CeStateMonitor.java
+++ b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/CeStateMonitor.java
@@ -19,7 +19,8 @@
  */
 package org.sonar.server.platform.monitoring;
 
-import java.util.LinkedHashMap;
+import com.google.common.base.Optional;
+import java.util.Map;
 import org.sonar.process.ProcessId;
 import org.sonar.process.jmx.JmxConnection;
 import org.sonar.process.jmx.JmxConnectionFactory;
@@ -38,9 +39,12 @@ public class CeStateMonitor implements Monitor {
   }
 
   @Override
-  public LinkedHashMap<String, Object> attributes() {
+  public Optional<Map<String, Object>> attributes() {
     try (JmxConnection connection = jmxConnectionFactory.create(ProcessId.COMPUTE_ENGINE)) {
-      return new LinkedHashMap<>(connection.getSystemState());
+      if (connection == null) {
+        return Optional.absent();
+      }
+      return Optional.of(connection.getSystemState());
     }
   }
 }
diff --git a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/CeTasksMonitor.java b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/CeTasksMonitor.java
index 77c1af84c53..fbdd08ba5dd 100644
--- a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/CeTasksMonitor.java
+++ b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/CeTasksMonitor.java
@@ -19,7 +19,9 @@
  */
 package org.sonar.server.platform.monitoring;
 
+import com.google.common.base.Optional;
 import java.util.LinkedHashMap;
+import java.util.Map;
 import org.sonar.process.ProcessId;
 import org.sonar.process.jmx.CeTasksMBean;
 import org.sonar.process.jmx.JmxConnection;
@@ -27,6 +29,8 @@ import org.sonar.process.jmx.JmxConnectionFactory;
 
 public class CeTasksMonitor implements Monitor {
 
+  private static final int NUMBER_OF_ATTRIBUTES = 6;
+
   private final JmxConnectionFactory jmxConnectionFactory;
 
   public CeTasksMonitor(JmxConnectionFactory jmxConnectionFactory) {
@@ -39,9 +43,12 @@ public class CeTasksMonitor implements Monitor {
   }
 
   @Override
-  public LinkedHashMap<String, Object> attributes() {
+  public Optional<Map<String, Object>> attributes() {
     try (JmxConnection connection = jmxConnectionFactory.create(ProcessId.COMPUTE_ENGINE)) {
-      LinkedHashMap<String, Object> result = new LinkedHashMap<>();
+      if (connection == null) {
+        return Optional.absent();
+      }
+      Map<String, Object> result = new LinkedHashMap<>(NUMBER_OF_ATTRIBUTES);
       CeTasksMBean ceMBean = connection.getMBean(CeTasksMBean.OBJECT_NAME, CeTasksMBean.class);
       result.put("Pending", ceMBean.getPendingCount());
       result.put("In Progress", ceMBean.getInProgressCount());
@@ -49,7 +56,7 @@ public class CeTasksMonitor implements Monitor {
       result.put("Processed With Error", ceMBean.getErrorCount());
       result.put("Processing Time (ms)", ceMBean.getProcessingTime());
       result.put("Worker Count", ceMBean.getWorkerCount());
-      return result;
+      return Optional.of(result);
     }
   }
 }
diff --git a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/DatabaseMonitor.java b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/DatabaseMonitor.java
index ceb0caf6ff0..f71f841b6e6 100644
--- a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/DatabaseMonitor.java
+++ b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/DatabaseMonitor.java
@@ -19,6 +19,7 @@
  */
 package org.sonar.server.platform.monitoring;
 
+import com.google.common.base.Optional;
 import java.sql.Connection;
 import java.sql.DatabaseMetaData;
 import java.sql.SQLException;
@@ -100,11 +101,11 @@ public class DatabaseMonitor extends BaseMonitorMBean implements DatabaseMonitor
   }
 
   @Override
-  public LinkedHashMap<String, Object> attributes() {
-    LinkedHashMap<String, Object> attributes = new LinkedHashMap<>();
+  public Optional<Map<String, Object>> attributes() {
+    Map<String, Object> attributes = new LinkedHashMap<>();
     completeDbAttributes(attributes);
     completePoolAttributes(attributes);
-    return attributes;
+    return Optional.of(attributes);
   }
 
   private void completePoolAttributes(Map<String, Object> attributes) {
diff --git a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/EsMonitor.java b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/EsMonitor.java
index 0317ba2c1b0..686ae56880a 100644
--- a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/EsMonitor.java
+++ b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/EsMonitor.java
@@ -19,6 +19,7 @@
  */
 package org.sonar.server.platform.monitoring;
 
+import com.google.common.base.Optional;
 import java.util.LinkedHashMap;
 import java.util.Map;
 import org.elasticsearch.action.admin.cluster.health.ClusterHealthStatus;
@@ -71,20 +72,22 @@ public class EsMonitor extends BaseMonitorMBean implements EsMonitorMBean {
   }
 
   @Override
-  public LinkedHashMap<String, Object> attributes() {
-    LinkedHashMap<String, Object> attributes = new LinkedHashMap<>();
+  public Optional<Map<String, Object>> attributes() {
+    Map<String, Object> attributes = new LinkedHashMap<>();
 
     try (JmxConnection connection = jmxConnectionFactory.create(ProcessId.ELASTICSEARCH)) {
-      EsSettingsMBean mbean = connection.getMBean(EsSettingsMBean.OBJECT_NAME, EsSettingsMBean.class);
-      attributes.put("Cluster Name", mbean.getClusterName());
-      attributes.put("Node Name", mbean.getNodeName());
-      attributes.put("HTTP Port", mbean.getHttpPort());
+      if (connection != null) {
+        EsSettingsMBean mbean = connection.getMBean(EsSettingsMBean.OBJECT_NAME, EsSettingsMBean.class);
+        attributes.put("Cluster Name", mbean.getClusterName());
+        attributes.put("Node Name", mbean.getNodeName());
+        attributes.put("HTTP Port", mbean.getHttpPort());
+      }
     }
     attributes.put("State", getStateAsEnum());
     attributes.put("Indices", indexAttributes());
     attributes.put("Number of Nodes", getNumberOfNodes());
     attributes.put("Nodes", nodeAttributes());
-    return attributes;
+    return Optional.of(attributes);
   }
 
   private LinkedHashMap<String, LinkedHashMap<String, Object>> indexAttributes() {
diff --git a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/EsStateMonitor.java b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/EsStateMonitor.java
index 0f8d60c4b07..779019be924 100644
--- a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/EsStateMonitor.java
+++ b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/EsStateMonitor.java
@@ -19,7 +19,8 @@
  */
 package org.sonar.server.platform.monitoring;
 
-import java.util.LinkedHashMap;
+import com.google.common.base.Optional;
+import java.util.Map;
 import org.sonar.process.ProcessId;
 import org.sonar.process.jmx.JmxConnection;
 import org.sonar.process.jmx.JmxConnectionFactory;
@@ -38,9 +39,12 @@ public class EsStateMonitor implements Monitor {
   }
 
   @Override
-  public LinkedHashMap<String, Object> attributes() {
+  public Optional<Map<String, Object>> attributes() {
     try (JmxConnection connection = jmxConnectionFactory.create(ProcessId.ELASTICSEARCH)) {
-      return new LinkedHashMap<>(connection.getSystemState());
+      if (connection == null) {
+        return Optional.absent();
+      }
+      return Optional.of(connection.getSystemState());
     }
   }
 }
diff --git a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/JmxConnectorProvider.java b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/JmxConnectionFactoryProvider.java
index 2bc9d247607..ebc98c1dddf 100644
--- a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/JmxConnectorProvider.java
+++ b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/JmxConnectionFactoryProvider.java
@@ -27,7 +27,7 @@ import org.sonar.process.jmx.JmxConnectionFactory;
 import static com.google.common.base.Preconditions.checkArgument;
 import static org.sonar.process.ProcessEntryPoint.PROPERTY_SHARED_PATH;
 
-public class JmxConnectorProvider extends ProviderAdapter {
+public class JmxConnectionFactoryProvider extends ProviderAdapter {
 
   private JmxConnectionFactory singleton = null;
 
diff --git a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/JvmPropsMonitor.java b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/JvmPropsMonitor.java
index 3d4b33e292b..26f642b7e6b 100644
--- a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/JvmPropsMonitor.java
+++ b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/JvmPropsMonitor.java
@@ -19,11 +19,10 @@
  */
 package org.sonar.server.platform.monitoring;
 
-import com.google.common.collect.Maps;
-import java.util.LinkedHashMap;
+import com.google.common.base.Optional;
 import java.util.Map;
 import java.util.Objects;
-import java.util.SortedMap;
+import java.util.TreeMap;
 
 public class JvmPropsMonitor implements Monitor {
   @Override
@@ -32,11 +31,11 @@ public class JvmPropsMonitor implements Monitor {
   }
 
   @Override
-  public LinkedHashMap<String, Object> attributes() {
-    SortedMap<String, Object> sortedProps = Maps.newTreeMap();
+  public Optional<Map<String, Object>> attributes() {
+    Map<String, Object> sortedProps = new TreeMap<>();
     for (Map.Entry<Object, Object> systemProp : System.getProperties().entrySet()) {
       sortedProps.put(Objects.toString(systemProp.getKey()), Objects.toString(systemProp.getValue()));
     }
-    return new LinkedHashMap<>(sortedProps);
+    return Optional.of(sortedProps);
   }
 }
diff --git a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/Monitor.java b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/Monitor.java
index 4ab48a74d56..c87db9ad8f4 100644
--- a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/Monitor.java
+++ b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/Monitor.java
@@ -19,13 +19,13 @@
  */
 package org.sonar.server.platform.monitoring;
 
+import com.google.common.base.Optional;
+import java.util.Map;
 import org.sonar.api.server.ServerSide;
 import org.sonar.server.platform.ws.InfoAction;
 
-import java.util.LinkedHashMap;
-
 /**
- * Any component that is involved in the informations returned by the web service api/system/info
+ * Any component that is involved in the information returned by the web service api/system/info
  */
 @ServerSide
 public interface Monitor {
@@ -36,7 +36,10 @@ public interface Monitor {
 
   /**
    * Type of attribute values must be supported by {@link org.sonar.api.utils.text.JsonWriter#valueObject(Object)}
-   * because of JSON export by {@link InfoAction}
+   * because of JSON export by {@link InfoAction}.
+   *
+   * @return map of attributes, or Optional.absent() if the monitored component is not up. In the latter case
+   * nothing is returned in the web service api/system/info.
    */
-  LinkedHashMap<String, Object> attributes();
+  Optional<Map<String, Object>> attributes();
 }
diff --git a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/PluginsMonitor.java b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/PluginsMonitor.java
index 4bd683e8912..6edb3cef096 100644
--- a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/PluginsMonitor.java
+++ b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/PluginsMonitor.java
@@ -19,7 +19,9 @@
  */
 package org.sonar.server.platform.monitoring;
 
+import com.google.common.base.Optional;
 import java.util.LinkedHashMap;
+import java.util.Map;
 import org.sonar.core.platform.PluginInfo;
 import org.sonar.core.platform.PluginRepository;
 import org.sonar.updatecenter.common.Version;
@@ -40,8 +42,8 @@ public class PluginsMonitor implements Monitor {
   }
 
   @Override
-  public LinkedHashMap<String, Object> attributes() {
-    LinkedHashMap<String, Object> attributes = new LinkedHashMap<>();
+  public Optional<Map<String, Object>> attributes() {
+    Map<String, Object> attributes = new LinkedHashMap<>();
     for (PluginInfo plugin : repository.getPluginInfos()) {
       LinkedHashMap<String, Object> pluginAttributes = new LinkedHashMap<>();
       pluginAttributes.put("Name", plugin.getName());
@@ -51,6 +53,6 @@ public class PluginsMonitor implements Monitor {
       }
       attributes.put(plugin.getKey(), pluginAttributes);
     }
-    return attributes;
+    return Optional.of(attributes);
   }
 }
diff --git a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/SonarQubeMonitor.java b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/SonarQubeMonitor.java
index 51605634647..7d6c3bd00ba 100644
--- a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/SonarQubeMonitor.java
+++ b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/SonarQubeMonitor.java
@@ -19,8 +19,10 @@
  */
 package org.sonar.server.platform.monitoring;
 
+import com.google.common.base.Optional;
 import java.io.File;
 import java.util.LinkedHashMap;
+import java.util.Map;
 import org.sonar.api.CoreProperties;
 import org.sonar.api.config.Settings;
 import org.sonar.api.platform.Server;
@@ -95,8 +97,8 @@ public class SonarQubeMonitor extends BaseMonitorMBean implements SonarQubeMonit
   }
 
   @Override
-  public LinkedHashMap<String, Object> attributes() {
-    LinkedHashMap<String, Object> attributes = new LinkedHashMap<>();
+  public Optional<Map<String, Object>> attributes() {
+    Map<String, Object> attributes = new LinkedHashMap<>();
     attributes.put("Server ID", getServerId());
     attributes.put("Version", getVersion());
     attributes.put("External User Authentication", getExternalUserAuthentication());
@@ -109,7 +111,7 @@ public class SonarQubeMonitor extends BaseMonitorMBean implements SonarQubeMonit
     attributes.put("Temp Dir", settings.getString(ProcessProperties.PATH_TEMP));
     attributes.put("Logs Dir", settings.getString(ProcessProperties.PATH_LOGS));
     attributes.put("Logs Level", getLogLevel());
-    return attributes;
+    return Optional.of(attributes);
 
   }
 }
diff --git a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/SystemMonitor.java b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/SystemMonitor.java
index 30849f76698..d7d279d94c9 100644
--- a/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/SystemMonitor.java
+++ b/server/sonar-server/src/main/java/org/sonar/server/platform/monitoring/SystemMonitor.java
@@ -19,8 +19,7 @@
  */
 package org.sonar.server.platform.monitoring;
 
-import org.sonar.api.utils.System2;
-
+import com.google.common.base.Optional;
 import java.lang.management.ClassLoadingMXBean;
 import java.lang.management.ManagementFactory;
 import java.lang.management.MemoryMXBean;
@@ -28,6 +27,8 @@ import java.lang.management.RuntimeMXBean;
 import java.lang.management.ThreadMXBean;
 import java.util.Date;
 import java.util.LinkedHashMap;
+import java.util.Map;
+import org.sonar.api.utils.System2;
 
 import static org.sonar.api.utils.DateUtils.formatDateTime;
 
@@ -52,8 +53,8 @@ public class SystemMonitor implements Monitor {
   }
 
   @Override
-  public LinkedHashMap<String, Object> attributes() {
-    LinkedHashMap<String, Object> attributes = new LinkedHashMap<>();
+  public Optional<Map<String, Object>> attributes() {
+    Map<String, Object> attributes = new LinkedHashMap<>();
     attributes.put("System Date", formatDateTime(new Date(system.now())));
     attributes.put("Start Time", formatDateTime(new Date(runtimeMXBean().getStartTime())));
     attributes.put("JVM Vendor", runtimeMXBean().getVmVendor());
@@ -75,7 +76,7 @@ public class SystemMonitor implements Monitor {
     attributes.put("Threads", threadMXBean().getThreadCount());
     attributes.put("Threads Peak", threadMXBean().getPeakThreadCount());
     attributes.put("Daemon Thread", threadMXBean().getDaemonThreadCount());
-    return attributes;
+    return Optional.of(attributes);
   }
 
   private static RuntimeMXBean runtimeMXBean() {
diff --git a/server/sonar-server/src/main/java/org/sonar/server/platform/platformlevel/PlatformLevel4.java b/server/sonar-server/src/main/java/org/sonar/server/platform/platformlevel/PlatformLevel4.java
index e8ea9752617..f5d88c657fc 100644
--- a/server/sonar-server/src/main/java/org/sonar/server/platform/platformlevel/PlatformLevel4.java
+++ b/server/sonar-server/src/main/java/org/sonar/server/platform/platformlevel/PlatformLevel4.java
@@ -160,7 +160,7 @@ import org.sonar.server.platform.monitoring.CeTasksMonitor;
 import org.sonar.server.platform.monitoring.DatabaseMonitor;
 import org.sonar.server.platform.monitoring.EsMonitor;
 import org.sonar.server.platform.monitoring.EsStateMonitor;
-import org.sonar.server.platform.monitoring.JmxConnectorProvider;
+import org.sonar.server.platform.monitoring.JmxConnectionFactoryProvider;
 import org.sonar.server.platform.monitoring.JvmPropsMonitor;
 import org.sonar.server.platform.monitoring.PluginsMonitor;
 import org.sonar.server.platform.monitoring.SonarQubeMonitor;
@@ -653,7 +653,7 @@ public class PlatformLevel4 extends PlatformLevel {
       TypeValidationModule.class,
 
       // System
-      new JmxConnectorProvider(),
+      new JmxConnectionFactoryProvider(),
       ServerLogging.class,
       RestartAction.class,
       InfoAction.class,
diff --git a/server/sonar-server/src/main/java/org/sonar/server/platform/ws/InfoAction.java b/server/sonar-server/src/main/java/org/sonar/server/platform/ws/InfoAction.java
index 3a4135818be..3512a9eb632 100644
--- a/server/sonar-server/src/main/java/org/sonar/server/platform/ws/InfoAction.java
+++ b/server/sonar-server/src/main/java/org/sonar/server/platform/ws/InfoAction.java
@@ -19,6 +19,7 @@
  */
 package org.sonar.server.platform.ws;
 
+import com.google.common.base.Optional;
 import java.util.Map;
 import org.sonar.api.server.ws.Request;
 import org.sonar.api.server.ws.Response;
@@ -63,12 +64,15 @@ public class InfoAction implements SystemWsAction {
   private void writeJson(JsonWriter json) {
     json.beginObject();
     for (Monitor monitor : monitors) {
-      json.name(monitor.name());
-      json.beginObject();
-      for (Map.Entry<String, Object> attribute : monitor.attributes().entrySet()) {
-        json.name(attribute.getKey()).valueObject(attribute.getValue());
+      Optional<Map<String, Object>> attributes = monitor.attributes();
+      if (attributes.isPresent()) {
+        json.name(monitor.name());
+        json.beginObject();
+        for (Map.Entry<String, Object> attribute : attributes.get().entrySet()) {
+          json.name(attribute.getKey()).valueObject(attribute.getValue());
+        }
+        json.endObject();
       }
-      json.endObject();
     }
     json.endObject();
   }
diff --git a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/CeDatabaseMonitorTest.java b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/CeDatabaseMonitorTest.java
index 4c2ce9ed035..9758471ffcb 100644
--- a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/CeDatabaseMonitorTest.java
+++ b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/CeDatabaseMonitorTest.java
@@ -19,7 +19,8 @@
  */
 package org.sonar.server.platform.monitoring;
 
-import java.util.LinkedHashMap;
+import com.google.common.base.Optional;
+import java.util.Map;
 import org.junit.Test;
 import org.mockito.Mockito;
 import org.sonar.process.ProcessId;
@@ -41,13 +42,20 @@ public class CeDatabaseMonitorTest {
   }
 
   @Test
-  public void testAttributes() {
+  public void attributes() {
     CeDatabaseMBean mbean = mock(CeDatabaseMBean.class, Mockito.RETURNS_DEFAULTS);
 
     when(jmxConnectionFactory.create(ProcessId.COMPUTE_ENGINE).getMBean(CeDatabaseMBean.OBJECT_NAME, CeDatabaseMBean.class))
       .thenReturn(mbean);
-    LinkedHashMap<String, Object> attributes = underTest.attributes();
-    assertThat(attributes).containsKeys("Pool Initial Size", "Pool Active Connections");
-    assertThat(attributes).hasSize(9);
+    Optional<Map<String, Object>> attributes = underTest.attributes();
+    assertThat(attributes.get()).containsKeys("Pool Initial Size", "Pool Active Connections");
+    assertThat(attributes.get()).hasSize(9);
+  }
+
+  @Test
+  public void absent_attributes_if_CE_is_down() {
+    when(jmxConnectionFactory.create(ProcessId.COMPUTE_ENGINE)).thenReturn(null);
+    Optional<Map<String, Object>> attributes = underTest.attributes();
+    assertThat(attributes.isPresent()).isFalse();
   }
 }
diff --git a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/CeStateMonitorTest.java b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/CeStateMonitorTest.java
index 5db51a693fa..1154bcff55c 100644
--- a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/CeStateMonitorTest.java
+++ b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/CeStateMonitorTest.java
@@ -19,8 +19,9 @@
  */
 package org.sonar.server.platform.monitoring;
 
+import com.google.common.base.Optional;
 import com.google.common.collect.ImmutableSortedMap;
-import java.util.LinkedHashMap;
+import java.util.Map;
 import org.assertj.core.data.MapEntry;
 import org.junit.Test;
 import org.mockito.Mockito;
@@ -45,9 +46,16 @@ public class CeStateMonitorTest {
   public void testAttributes() {
     when(jmxConnectionFactory.create(ProcessId.COMPUTE_ENGINE).getSystemState()).thenReturn(ImmutableSortedMap.<String, Object>of(
       "foo", "foo_val", "bar", "bar_val"));
-    LinkedHashMap<String, Object> attributes = underTest.attributes();
-    assertThat(attributes).containsExactly(
+    Optional<Map<String, Object>> attributes = underTest.attributes();
+    assertThat(attributes.get()).containsExactly(
       MapEntry.entry("bar", "bar_val"),
       MapEntry.entry("foo", "foo_val"));
   }
+
+  @Test
+  public void absent_attributes_if_CE_is_down() {
+    when(jmxConnectionFactory.create(ProcessId.COMPUTE_ENGINE)).thenReturn(null);
+    Optional<Map<String, Object>> attributes = underTest.attributes();
+    assertThat(attributes.isPresent()).isFalse();
+  }
 }
diff --git a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/CeTasksMonitorTest.java b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/CeTasksMonitorTest.java
index cf1902601ae..c9d7626aa5a 100644
--- a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/CeTasksMonitorTest.java
+++ b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/CeTasksMonitorTest.java
@@ -19,7 +19,8 @@
  */
 package org.sonar.server.platform.monitoring;
 
-import java.util.LinkedHashMap;
+import com.google.common.base.Optional;
+import java.util.Map;
 import org.junit.Test;
 import org.mockito.Mockito;
 import org.sonar.process.ProcessId;
@@ -46,8 +47,15 @@ public class CeTasksMonitorTest {
 
     when(jmxConnectionFactory.create(ProcessId.COMPUTE_ENGINE).getMBean(CeTasksMBean.OBJECT_NAME, CeTasksMBean.class))
       .thenReturn(mbean);
-    LinkedHashMap<String, Object> attributes = underTest.attributes();
-    assertThat(attributes).containsKeys("Pending");
-    assertThat(attributes).hasSize(6);
+    Optional<Map<String, Object>> attributes = underTest.attributes();
+    assertThat(attributes.get()).containsKeys("Pending");
+    assertThat(attributes.get()).hasSize(6);
+  }
+
+  @Test
+  public void absent_attributes_if_CE_is_down() {
+    when(jmxConnectionFactory.create(ProcessId.COMPUTE_ENGINE)).thenReturn(null);
+    Optional<Map<String, Object>> attributes = underTest.attributes();
+    assertThat(attributes.isPresent()).isFalse();
   }
 }
diff --git a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/DatabaseMonitorTest.java b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/DatabaseMonitorTest.java
index 1e7cb5eccc5..5ed384ce7b0 100644
--- a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/DatabaseMonitorTest.java
+++ b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/DatabaseMonitorTest.java
@@ -19,7 +19,7 @@
  */
 package org.sonar.server.platform.monitoring;
 
-import java.util.LinkedHashMap;
+import java.util.Map;
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
@@ -49,7 +49,7 @@ public class DatabaseMonitorTest {
 
   @Test
   public void db_info() {
-    LinkedHashMap<String, Object> attributes = underTest.attributes();
+    Map<String, Object> attributes = underTest.attributes().get();
     assertThat(attributes.get("Database")).isEqualTo("H2");
     assertThat(attributes.get("Database Version").toString()).startsWith("1.");
     assertThat(attributes.get("Username")).isEqualTo("SONAR");
@@ -58,7 +58,7 @@ public class DatabaseMonitorTest {
 
   @Test
   public void pool_info() {
-    LinkedHashMap<String, Object> attributes = underTest.attributes();
+    Map<String, Object> attributes = underTest.attributes().get();
     assertThat((int) attributes.get("Pool Max Connections")).isGreaterThan(0);
   }
 }
diff --git a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/EsMonitorTest.java b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/EsMonitorTest.java
index 0716a6415a8..6379c5d0779 100644
--- a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/EsMonitorTest.java
+++ b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/EsMonitorTest.java
@@ -19,7 +19,6 @@
  */
 package org.sonar.server.platform.monitoring;
 
-import java.util.LinkedHashMap;
 import java.util.Map;
 import org.elasticsearch.action.admin.cluster.health.ClusterHealthStatus;
 import org.junit.Before;
@@ -59,7 +58,7 @@ public class EsMonitorTest {
 
   @Test
   public void cluster_attributes() {
-    LinkedHashMap<String, Object> attributes = underTest.attributes();
+    Map<String, Object> attributes = underTest.attributes().get();
     assertThat(underTest.getState()).isEqualTo(ClusterHealthStatus.GREEN.name());
     assertThat(attributes.get("State")).isEqualTo(ClusterHealthStatus.GREEN);
     assertThat(attributes.get("Number of Nodes")).isEqualTo(1);
@@ -67,7 +66,7 @@ public class EsMonitorTest {
 
   @Test
   public void node_attributes() {
-    LinkedHashMap<String, Object> attributes = underTest.attributes();
+    Map<String, Object> attributes = underTest.attributes().get();
     Map nodesAttributes = (Map) attributes.get("Nodes");
 
     // one node
@@ -79,7 +78,7 @@ public class EsMonitorTest {
 
   @Test
   public void index_attributes() {
-    LinkedHashMap<String, Object> attributes = underTest.attributes();
+    Map<String, Object> attributes = underTest.attributes().get();
     Map indicesAttributes = (Map) attributes.get("Indices");
 
     // one index "issues"
diff --git a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/EsStateMonitorTest.java b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/EsStateMonitorTest.java
index e06f5c9c111..7618fedfbd8 100644
--- a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/EsStateMonitorTest.java
+++ b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/EsStateMonitorTest.java
@@ -19,8 +19,9 @@
  */
 package org.sonar.server.platform.monitoring;
 
+import com.google.common.base.Optional;
 import com.google.common.collect.ImmutableSortedMap;
-import java.util.LinkedHashMap;
+import java.util.Map;
 import org.assertj.core.data.MapEntry;
 import org.junit.Test;
 import org.mockito.Mockito;
@@ -44,9 +45,16 @@ public class EsStateMonitorTest {
   public void testAttributes() {
     when(jmxConnectionFactory.create(ProcessId.ELASTICSEARCH).getSystemState()).thenReturn(ImmutableSortedMap.<String, Object>of(
       "foo", "foo_val", "bar", "bar_val"));
-    LinkedHashMap<String, Object> attributes = underTest.attributes();
-    assertThat(attributes).containsExactly(
+    Optional<Map<String, Object>> attributes = underTest.attributes();
+    assertThat(attributes.get()).containsExactly(
       MapEntry.entry("bar", "bar_val"),
       MapEntry.entry("foo", "foo_val"));
   }
+
+  @Test
+  public void absent_attributes_if_CE_is_down() {
+    when(jmxConnectionFactory.create(ProcessId.ELASTICSEARCH)).thenReturn(null);
+    Optional<Map<String, Object>> attributes = underTest.attributes();
+    assertThat(attributes.isPresent()).isFalse();
+  }
 }
diff --git a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/FakeMonitor.java b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/FakeMonitor.java
index 885ab6866a4..879b65f8405 100644
--- a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/FakeMonitor.java
+++ b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/FakeMonitor.java
@@ -19,7 +19,9 @@
  */
 package org.sonar.server.platform.monitoring;
 
-import java.util.LinkedHashMap;
+import com.google.common.base.Optional;
+import java.util.Collections;
+import java.util.Map;
 
 public class FakeMonitor extends BaseMonitorMBean implements FakeMonitorMBean {
 
@@ -34,7 +36,7 @@ public class FakeMonitor extends BaseMonitorMBean implements FakeMonitorMBean {
   }
 
   @Override
-  public LinkedHashMap<String, Object> attributes() {
-    return new LinkedHashMap<>();
+  public Optional<Map<String, Object>> attributes() {
+    return Optional.of(Collections.<String, Object>emptyMap());
   }
 }
diff --git a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/JmxConnectionFactoryProviderTest.java b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/JmxConnectionFactoryProviderTest.java
index 5a461bc21c3..03998a76cde 100644
--- a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/JmxConnectionFactoryProviderTest.java
+++ b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/JmxConnectionFactoryProviderTest.java
@@ -34,7 +34,7 @@ public class JmxConnectionFactoryProviderTest {
   public ExpectedException expectedException = ExpectedException.none();
 
   Settings settings = new Settings();
-  JmxConnectorProvider underTest = new JmxConnectorProvider();
+  JmxConnectionFactoryProvider underTest = new JmxConnectionFactoryProvider();
 
   @Test
   public void provide_JmxConnector() {
diff --git a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/JvmPropsMonitorTest.java b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/JvmPropsMonitorTest.java
index 48ce163e151..0a534035280 100644
--- a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/JvmPropsMonitorTest.java
+++ b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/JvmPropsMonitorTest.java
@@ -19,7 +19,8 @@
  */
 package org.sonar.server.platform.monitoring;
 
-import java.util.LinkedHashMap;
+import com.google.common.base.Optional;
+import java.util.Map;
 import org.junit.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -35,8 +36,8 @@ public class JvmPropsMonitorTest {
 
   @Test
   public void attributes() {
-    LinkedHashMap<String, Object> attributes = underTest.attributes();
+    Optional<Map<String, Object>> attributes = underTest.attributes();
 
-    assertThat(attributes).containsKeys("java.vm.vendor", "os.name");
+    assertThat(attributes.get()).containsKeys("java.vm.vendor", "os.name");
   }
 }
diff --git a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/PluginsMonitorTest.java b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/PluginsMonitorTest.java
index 04501cc361a..c5c4b1a4f51 100644
--- a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/PluginsMonitorTest.java
+++ b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/PluginsMonitorTest.java
@@ -19,15 +19,13 @@
  */
 package org.sonar.server.platform.monitoring;
 
+import java.util.Arrays;
+import java.util.Map;
 import org.junit.Test;
 import org.sonar.core.platform.PluginInfo;
 import org.sonar.core.platform.PluginRepository;
 import org.sonar.updatecenter.common.Version;
 
-import java.util.Arrays;
-import java.util.LinkedHashMap;
-import java.util.Map;
-
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
@@ -54,7 +52,7 @@ public class PluginsMonitorTest {
       new PluginInfo("no-version")
         .setName("No Version")));
 
-    LinkedHashMap<String, Object> attributes = underTest.attributes();
+    Map<String, Object> attributes = underTest.attributes().get();
 
     assertThat(attributes).containsKeys("key-1", "key-2");
     assertThat((Map) attributes.get("key-1"))
diff --git a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/SonarQubeMonitorTest.java b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/SonarQubeMonitorTest.java
index 9c9f91999d9..70155ae82f9 100644
--- a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/SonarQubeMonitorTest.java
+++ b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/SonarQubeMonitorTest.java
@@ -19,8 +19,9 @@
  */
 package org.sonar.server.platform.monitoring;
 
+import com.google.common.base.Optional;
 import java.io.File;
-import java.util.LinkedHashMap;
+import java.util.Map;
 import org.apache.commons.io.FileUtils;
 import org.junit.Before;
 import org.junit.Rule;
@@ -61,8 +62,8 @@ public class SonarQubeMonitorTest {
     when(server.getStartedAt()).thenReturn(DateUtils.parseDate("2015-01-01"));
     SonarQubeMonitor monitor = new SonarQubeMonitor(settings, new SecurityRealmFactory(settings), server, serverLogging);
 
-    LinkedHashMap<String, Object> attributes = monitor.attributes();
-    assertThat(attributes).containsKeys("Server ID", "Version");
+    Optional<Map<String, Object>> attributes = monitor.attributes();
+    assertThat(attributes.get()).containsKeys("Server ID", "Version");
   }
 
   @Test
@@ -73,8 +74,8 @@ public class SonarQubeMonitorTest {
     when(server.getRootDir()).thenReturn(rootDir);
     SonarQubeMonitor monitor = new SonarQubeMonitor(settings, new SecurityRealmFactory(settings), server, serverLogging);
 
-    LinkedHashMap<String, Object> attributes = monitor.attributes();
-    assertThat(attributes).containsEntry("Official Distribution", Boolean.TRUE);
+    Optional<Map<String, Object>> attributes = monitor.attributes();
+    assertThat(attributes.get()).containsEntry("Official Distribution", Boolean.TRUE);
   }
 
   @Test
@@ -84,15 +85,15 @@ public class SonarQubeMonitorTest {
     when(server.getRootDir()).thenReturn(rootDir);
     SonarQubeMonitor monitor = new SonarQubeMonitor(settings, new SecurityRealmFactory(settings), server, serverLogging);
 
-    LinkedHashMap<String, Object> attributes = monitor.attributes();
-    assertThat(attributes).containsEntry("Official Distribution", Boolean.FALSE);
+    Optional<Map<String, Object>> attributes = monitor.attributes();
+    assertThat(attributes.get()).containsEntry("Official Distribution", Boolean.FALSE);
   }
 
   @Test
   public void get_log_level() throws Exception {
     SonarQubeMonitor monitor = new SonarQubeMonitor(settings, new SecurityRealmFactory(settings), server, serverLogging);
 
-    LinkedHashMap<String, Object> attributes = monitor.attributes();
-    assertThat(attributes).containsEntry("Logs Level", "DEBUG");
+    Optional<Map<String, Object>> attributes = monitor.attributes();
+    assertThat(attributes.get()).containsEntry("Logs Level", "DEBUG");
   }
 }
diff --git a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/SystemMonitorTest.java b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/SystemMonitorTest.java
index 0232572647b..07510691802 100644
--- a/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/SystemMonitorTest.java
+++ b/server/sonar-server/src/test/java/org/sonar/server/platform/monitoring/SystemMonitorTest.java
@@ -19,10 +19,9 @@
  */
 package org.sonar.server.platform.monitoring;
 
+import java.util.Map;
 import org.junit.Test;
 
-import java.util.LinkedHashMap;
-
 import static org.assertj.core.api.Assertions.assertThat;
 
 public class SystemMonitorTest {
@@ -36,7 +35,7 @@ public class SystemMonitorTest {
 
   @Test
   public void system_properties() {
-    LinkedHashMap<String, Object> attributes = underTest.attributes();
+    Map<String, Object> attributes = underTest.attributes().get();
 
     assertThat(attributes).containsKeys("System Date", "Processors");
   }
diff --git a/server/sonar-server/src/test/java/org/sonar/server/platform/ws/InfoActionTest.java b/server/sonar-server/src/test/java/org/sonar/server/platform/ws/InfoActionTest.java
index 539cc6440f9..41a0a6788b9 100644
--- a/server/sonar-server/src/test/java/org/sonar/server/platform/ws/InfoActionTest.java
+++ b/server/sonar-server/src/test/java/org/sonar/server/platform/ws/InfoActionTest.java
@@ -19,7 +19,9 @@
  */
 package org.sonar.server.platform.ws;
 
+import com.google.common.base.Optional;
 import java.util.LinkedHashMap;
+import java.util.Map;
 import org.junit.Rule;
 import org.junit.Test;
 import org.sonar.api.server.ws.Request;
@@ -42,7 +44,8 @@ public class InfoActionTest {
 
   Monitor monitor1 = mock(Monitor.class);
   Monitor monitor2 = mock(Monitor.class);
-  InfoAction underTest = new InfoAction(userSessionRule, monitor1, monitor2);
+  Monitor monitor3 = mock(Monitor.class);
+  InfoAction underTest = new InfoAction(userSessionRule, monitor1, monitor2, monitor3);
 
   @Test(expected = ForbiddenException.class)
   public void should_fail_when_does_not_have_admin_right() {
@@ -55,18 +58,21 @@ public class InfoActionTest {
   public void write_json() {
     userSessionRule.setGlobalPermissions(GlobalPermissions.SYSTEM_ADMIN);
 
-    LinkedHashMap<String, Object> attributes1 = new LinkedHashMap<>();
+    Map<String, Object> attributes1 = new LinkedHashMap<>();
     attributes1.put("foo", "bar");
-    LinkedHashMap<String, Object> attributes2 = new LinkedHashMap<>();
+    Map<String, Object> attributes2 = new LinkedHashMap<>();
     attributes2.put("one", 1);
     attributes2.put("two", 2);
     when(monitor1.name()).thenReturn("Monitor One");
-    when(monitor1.attributes()).thenReturn(attributes1);
+    when(monitor1.attributes()).thenReturn(Optional.of(attributes1));
     when(monitor2.name()).thenReturn("Monitor Two");
-    when(monitor2.attributes()).thenReturn(attributes2);
+    when(monitor2.attributes()).thenReturn(Optional.of(attributes2));
+    when(monitor3.name()).thenReturn("Monitor Three");
+    when(monitor3.attributes()).thenReturn(Optional.<Map<String, Object>>absent());
 
     WsTester.TestResponse response = new WsTester.TestResponse();
     underTest.handle(new SimpleGetRequest(), response);
+    // response does not contain empty "Monitor Three"
     assertThat(response.outputAsString()).isEqualTo("{\"Monitor One\":{\"foo\":\"bar\"},\"Monitor Two\":{\"one\":1,\"two\":2}}");
   }
 }
diff --git a/server/sonar-web/src/main/js/apps/system/main.js b/server/sonar-web/src/main/js/apps/system/main.js
index ea003bb7de6..65cafba2d93 100644
--- a/server/sonar-web/src/main/js/apps/system/main.js
+++ b/server/sonar-web/src/main/js/apps/system/main.js
@@ -25,7 +25,7 @@ import { translate } from '../../helpers/l10n';
 import RestartModal from '../../components/RestartModal';
 
 const SECTIONS_ORDER = ['SonarQube', 'Database', 'Plugins', 'System', 'Elasticsearch State', 'Elasticsearch',
-  'Compute Engine Tasks', 'Compute Engine State', 'Compute Engine Database', 'JvmProperties'];
+  'Compute Engine Tasks', 'Compute Engine State', 'Compute Engine Database Connection', 'JvmProperties'];
 
 export default React.createClass({
   componentDidMount() {