Allow disabling of sigar via settings

Sigar can only be disabled by removing the binaries. This is tricky for our
tests and might cause a lot of trouble if a user wants or needs to do it.
This commit allows to disable sigar with a simple boolean flag in the settings.

Closes #9582

src/main/java/org/elasticsearch/bootstrap/Bootstrap.java

@@ -38,6 +38,7 @@ import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.env.Environment;
 import org.elasticsearch.monitor.jvm.JvmInfo;
 import org.elasticsearch.monitor.process.JmxProcessProbe;
+import org.elasticsearch.monitor.sigar.SigarService;
 import org.elasticsearch.node.Node;
 import org.elasticsearch.node.NodeBuilder;
 import org.elasticsearch.node.internal.InternalSettingsPreparer;
@@ -85,7 +86,8 @@ public class Bootstrap {
     }
     
     /** initialize native resources */
-    public static void initializeNatives(boolean mlockAll, boolean ctrlHandler) {
+    public static void initializeNatives(boolean mlockAll, boolean ctrlHandler, boolean loadSigar) {
+        final ESLogger logger = Loggers.getLogger(Bootstrap.class);
         // mlockall if requested
         if (mlockAll) {
             if (Constants.WINDOWS) {
@@ -98,7 +100,7 @@ public class Bootstrap {
         // check if the user is running as root, and bail
         if (Natives.definitelyRunningAsRoot()) {
             if (Boolean.parseBoolean(System.getProperty("es.insecure.allow.root"))) {
-                Loggers.getLogger(Bootstrap.class).warn("running as ROOT user. this is a bad idea!");
+                logger.warn("running as ROOT user. this is a bad idea!");
             } else {
                 throw new RuntimeException("don't run elasticsearch as root.");
             }
@@ -110,9 +112,7 @@ public class Bootstrap {
                 @Override
                 public boolean handle(int code) {
                     if (CTRL_CLOSE_EVENT == code) {
-                        ESLogger logger = Loggers.getLogger(Bootstrap.class);
                         logger.info("running graceful exit on windows");
-
                         Bootstrap.INSTANCE.stop();
                         return true;
                     }
@@ -128,12 +128,16 @@ public class Bootstrap {
             // we've already logged this.
         }
 
+        if (loadSigar) {
             // initialize sigar explicitly
             try {
                 Sigar.load();
-            Loggers.getLogger(Bootstrap.class).trace("sigar libraries loaded successfully");
+                logger.trace("sigar libraries loaded successfully");
             } catch (Throwable t) {
-            Loggers.getLogger(Bootstrap.class).trace("failed to load sigar libraries", t);
+                logger.trace("failed to load sigar libraries", t);
+            }
+        } else {
+            logger.trace("sigar not loaded, disabled via settings");
         }
 
         // init lucene random seed. it will use /dev/urandom where available:
@@ -142,7 +146,8 @@ public class Bootstrap {
 
     private void setup(boolean addShutdownHook, Settings settings, Environment environment) throws Exception {
         initializeNatives(settings.getAsBoolean("bootstrap.mlockall", false), 
-                          settings.getAsBoolean("bootstrap.ctrlhandler", true));
+                          settings.getAsBoolean("bootstrap.ctrlhandler", true),
+                          settings.getAsBoolean("bootstrap.sigar", true));
 
         if (addShutdownHook) {
             Runtime.getRuntime().addShutdownHook(new Thread() {

src/main/java/org/elasticsearch/monitor/sigar/SigarService.java

@@ -34,8 +34,8 @@ public class SigarService extends AbstractComponent {
     @Inject
     public SigarService(Settings settings) {
         super(settings);
-
         Sigar sigar = null;
+        if (settings.getAsBoolean("bootstrap.sigar", true)) {
             try {
                 sigar = new Sigar();
                 // call it to make sure the library was loaded
@@ -53,6 +53,7 @@ public class SigarService extends AbstractComponent {
                     }
                 }
             }
+        }
         this.sigar = sigar;
     }
 

src/test/java/org/elasticsearch/bootstrap/BootstrapForTesting.java

@@ -49,7 +49,7 @@ public class BootstrapForTesting {
 
     static {
         // just like bootstrap, initialize natives, then SM
-        Bootstrap.initializeNatives(true, true);
+        Bootstrap.initializeNatives(true, true, true);
 
         // make sure java.io.tmpdir exists always (in case code uses it in a static initializer)
         Path javaTmpDir = PathUtils.get(Objects.requireNonNull(System.getProperty("java.io.tmpdir"),

src/test/java/org/elasticsearch/test/InternalTestCluster.java

@@ -90,6 +90,7 @@ import org.elasticsearch.indices.breaker.CircuitBreakerService;
 import org.elasticsearch.indices.breaker.HierarchyCircuitBreakerService;
 import org.elasticsearch.indices.fielddata.cache.IndicesFieldDataCache;
 import org.elasticsearch.indices.recovery.RecoverySettings;
+import org.elasticsearch.monitor.sigar.SigarService;
 import org.elasticsearch.node.Node;
 import org.elasticsearch.node.service.NodeService;
 import org.elasticsearch.plugins.PluginsService;
@@ -277,6 +278,7 @@ public final class InternalTestCluster extends TestCluster {
                 builder.put("path.data", dataPath.toString());
             }
         }
+        builder.put("bootstrap.sigar", rarely());
         builder.put("path.home", baseDir);
         builder.put("path.repo", baseDir.resolve("repos"));
         builder.put("transport.tcp.port", BASE_PORT + "-" + (BASE_PORT+100));