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From "Uwe Schindler (JIRA)" <>
Subject [jira] [Updated] (LUCENE-5086) RamUsageEstimator causes AWT classes to be loaded by calling ManagementFactory#getPlatformMBeanServer
Date Fri, 05 Jul 2013 08:17:48 GMT


Uwe Schindler updated LUCENE-5086:

    Attachment: LUCENE-5086-trunk.patch

Some restructuring and preventing a useless NPE that needs to be catched on non-Hotspot JVMs.
I also removed the separate private method and made the whole thing with nested catches like
at the other places in the static {} initializer (I don't like class' methods called from
a static initializer). Also this one is easier to debug, as you can add printlns without working
around the "return" escape of the original method!

I tested on Windows:
- Oracle JDK 6u32 and 6u45 (64 bit) work, proprietary sunMF API used
- Oracle JDK 6u32, 32 bit is unsupported as before (the object alignment JVM option does not
exist at all, but also the sunMF API is used)
- Oracle JDK 7u25 (64 bit) works, new public Java 7 API is used (via reflection) or statically
typed in trunk
- All other JVMs are unsupported, but they don't have obejct alignment available

By the way: Our code looks better and more universal, because it does not rely on the management
bean to detect compressed oops. We "measure" them! So it also works with J9!
> RamUsageEstimator causes AWT classes to be loaded by calling ManagementFactory#getPlatformMBeanServer
> -----------------------------------------------------------------------------------------------------
>                 Key: LUCENE-5086
>                 URL:
>             Project: Lucene - Core
>          Issue Type: Improvement
>            Reporter: Shay Banon
>            Assignee: Dawid Weiss
>         Attachments: LUCENE-5086-branch4x.patch, LUCENE-5086-branch4x.patch, LUCENE-5086.patch,
LUCENE-5086-trunk.patch, LUCENE-5086-trunk.patch
> Yea, that type of day and that type of title :).
> Since the last update of Java 6 on OS X, I started to see an annoying icon pop up at
the doc whenever running elasticsearch. By default, all of our scripts add headless AWT flag
so people will probably not encounter it, but, it was strange that I saw it when before I
> I started to dig around, and saw that when RamUsageEstimator was being loaded, it was
causing AWT classes to be loaded. Further investigation showed that actually for some reason,
calling ManagementFactory#getPlatformMBeanServer now with the new Java version causes AWT
classes to be loaded (at least on the mac, haven't tested on other platforms yet). 
> There are several ways to try and solve it, for example, by identifying the bug in the
JVM itself, but I think that there should be a fix for it in Lucene itself, specifically since
there is no need to call #getPlatformMBeanServer to get the hotspot diagnostics one (its a
heavy call...).
> Here is a simple call that will allow to get the hotspot mxbean without using the #getPlatformMBeanServer
method, and not causing it to be loaded and loading all those nasty AWT classes:
> {code}
>     Object getHotSpotMXBean() {
>         try {
>             // Java 6
>             Class sunMF = Class.forName("");
>             return sunMF.getMethod("getDiagnosticMXBean").invoke(null);
>         } catch (Throwable t) {
>             // ignore
>         }
>         // potentially Java 7
>         try {
>             return ManagementFactory.class.getMethod("getPlatformMXBean", Class.class).invoke(null,
>         } catch (Throwable t) {
>             // ignore
>         }
>         return null;
>     }
> {code}

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