OperatingSystemMXBeanProvider: Don't throw IllegalStateException

If the implementation of OperatingSystemMXBeanProvider can't be
instantiated, simply return null and thus skip the CPU and file
descriptors metrics, rather than throwing IllegalStateException
which prevents the site from starting.

Bug: Issue 5727
Change-Id: I8c8e155c274e788dbea07c64ae1c95aac09df35b

1 files changed, 7 insertions, 7 deletions

diff --git a/gerrit-server/src/main/java/com/google/gerrit/metrics/proc/OperatingSystemMXBeanProvider.java b/gerrit-server/src/main/java/com/google/gerrit/metrics/proc/OperatingSystemMXBeanProvider.java
index 696a68734d..4eccf53109 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/metrics/proc/OperatingSystemMXBeanProvider.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/metrics/proc/OperatingSystemMXBeanProvider.java
@@ -14,8 +14,6 @@
 
 package com.google.gerrit.metrics.proc;
 
-import static com.google.common.base.Preconditions.checkState;
-
 import java.lang.management.ManagementFactory;
 import java.lang.management.OperatingSystemMXBean;
 import java.lang.reflect.Method;
@@ -40,10 +38,13 @@ class OperatingSystemMXBeanProvider {
               "com.sun.management.UnixOperatingSystemMXBean",
               "com.ibm.lang.management.UnixOperatingSystemMXBean")) {
         try {
-          Class.forName(name);
-          return new OperatingSystemMXBeanProvider(sys, name);
+          Class<?> impl = Class.forName(name);
+          if (impl.isInstance(sys)) {
+            return new OperatingSystemMXBeanProvider(sys);
+          }
         } catch (ReflectiveOperationException e) {
-          log.debug("No implementation for " + name);
+          log.debug(String.format(
+              "No implementation for %s: %s", name, e.getMessage()));
         }
       }
       log.warn("No implementation of UnixOperatingSystemMXBean found");
@@ -51,9 +52,8 @@ class OperatingSystemMXBeanProvider {
     }
   }
 
-  private OperatingSystemMXBeanProvider(OperatingSystemMXBean sys, String name)
+  private OperatingSystemMXBeanProvider(OperatingSystemMXBean sys)
       throws ReflectiveOperationException {
-    checkState(Class.forName(name).isInstance(sys));
     this.sys = sys;
     getProcessCpuTime =
         sys.getClass().getMethod("getProcessCpuTime", new Class[] {});