warn if mlockall is not working once enabled in settings (instead of debug logging), closes #1194.

config/elasticsearch.yml

@@ -7,18 +7,16 @@
 #path.work: /path/to/work
 #path.logs: /path/to/logs
 
+# Force all memory to be locked, forcing the JVM to never swap
+#bootstrap.mlockall: true
+
 # Gateway Settings
 #   Controls when to start the initial recovery process when starting a new cluster
+#   allowing for better reused of existing data during recovery.
 #gateway.recover_after_nodes: 1
 #gateway.recover_after_time: 5m
 #gateway.expected_nodes: 2
 
-# Force all memory to be locked, forcing JVM to never swap
-#   (make sure to set MIN and MAX mem to the same value)
-#   In order to see if this works or not, set the `common.jna` logging to DEBUG level.
-#   A solution to “Unknown mlockall error 0” can be to set ulimit -l unlimited.
-#bootstrap.mlockall: true
-
 # Controls the minimum number of master eligible nodes this node should "see"
 # in order to operate within the cluster.
 #   Set this to a higher value (2-4) when running more than 2 nodes in the cluster

modules/elasticsearch/src/main/java/org/elasticsearch/common/jna/CLibrary.java

@@ -40,9 +40,9 @@ public class CLibrary {
         try {
             Native.register("c");
         } catch (NoClassDefFoundError e) {
-            logger.debug("JNA not found. Native methods will be disabled.");
+            logger.warn("jna not found. native methods (mlockall) will be disabled.");
         } catch (UnsatisfiedLinkError e) {
-            logger.debug("Unable to link C library. Native methods will be disabled.");
+            logger.debug("unable to link C library. native methods (mlockall) will be disabled.");
         }
     }
 

modules/elasticsearch/src/main/java/org/elasticsearch/common/jna/Natives.java

@@ -43,12 +43,12 @@ public class Natives {
 
         if (errno != Integer.MIN_VALUE) {
             if (errno == CLibrary.ENOMEM && System.getProperty("os.name").toLowerCase().contains("linux")) {
-                logger.debug("Unable to lock JVM memory (ENOMEM)."
+                logger.warn("Unable to lock JVM memory (ENOMEM)."
                         + " This can result in part of the JVM being swapped out."
                         + " Increase RLIMIT_MEMLOCK or run elasticsearch as root.");
             } else if (!System.getProperty("os.name").toLowerCase().contains("mac")) {
                 // OS X allows mlockall to be called, but always returns an error
-                logger.debug("Unknown mlockall error " + errno);
+                logger.warn("Unknown mlockall error " + errno);
             }
         }
     }