com.oracle.svm.core.jdk.management

Class ManagementSupport

java.lang.Object

com.oracle.svm.core.jdk.management.ManagementSupport

public final class ManagementSupport
extends Object

This class provides the SVM support implementation for the MXBean that provide VM introspection, which is accessible in the JDK via ManagementFactory. There are two mostly independent parts: The beans (implementations of PlatformManagedObject) themselves; and the singleton MBean server. Support for PlatformManagedObject: All MXBean that provide VM introspection are allocated eagerly at image build time, and stored in ManagementSupport.platformManagedObjectsMap as well as ManagementSupport.platformManagedObjectsSet. The registration is decentralized: while some general beans are registered in this class, the OS specific and GC specific beans are registered in the respective OS or GC code. To find all registrations, look for the usages of ManagementSupport.addPlatformManagedObjectSingleton(java.lang.Class<T>, T) and ManagementSupport.addPlatformManagedObjectList(java.lang.Class<T>, java.util.List<T>). Eager allocation of all the beans avoids the complicated registry that the JDK maintains for lazy loading (the code in PlatformComponent - note that this code and even the package of the class is significantly different between JDK 8 and JDK 11). Support for ManagementFactory.getPlatformMBeanServer(): The MBeanServer that makes all MXBean available too is allocated lazily at run time. This has advantages and disadvantages. The MBeanServer and all the bean registrations is a quite heavyweight data structure. All the attributes and operations of the beans are stored in several nested hash maps. Putting all of that in the image heap would increase the image heap size, but also avoid the allocation at run time on first access. Unfortunately, there are also many additional global caches for bean and attribute lookup, for example in MXBeanLookup, MXBeanIntrospector, and MBeanServerFactory. Beans from the hosting VM that runs the image build must not be made available at runtime using these caches, i.e., a complicated re-build of the caches would be necessary at image build time. Therefore we opted to inialize the MBeanServer at run time. This has two important consequences: 1) There must not be any MBeanServer in the image heap, neither the singleton platform server nor a custom server created by the application. Classes that cache a MBeanServer in a static final field must be initialized at run time. 2) All the attribute lookup of the platform beans happens at run time during initialization. Attributes are found using reflection (enumerating all methods of the bean interface). So the attributes of the platform beans are only available via the MBeanServer if the methods are manually registered for reflection by the application. There is no automatic registration of all methods because that would lead to a significant number of unnecessary method registrations. It is cumbersome to access attributes of platform beans via the MBeanServer, getting the platform objects and directly calling methods on them is much easier and therefore the common use case. We therefore believe that the automatic reflection registration is indeed unnecessary.

Method Summary

Modifier and Type	Method and Description
<T extends PlatformManagedObject> void	addPlatformManagedObjectList(Class<T> clazz, List<T> objects) Adds the provided list of PlatformManagedObject for the provided interface and all its superinterfaces.
<T extends PlatformManagedObject> void	addPlatformManagedObjectSingleton(Class<T> clazz, T object) Registers a new singleton PlatformManagedObject for the provided interface and all its superinterfaces.
static ManagementSupport	getSingleton()
boolean	isAllowedPlatformManagedObject(PlatformManagedObject object)
void	noteThreadFinish(Thread thread)
void	noteThreadStart(Thread thread)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

getSingleton

public static ManagementSupport getSingleton()

addPlatformManagedObjectSingleton

public <T extends PlatformManagedObject> void addPlatformManagedObjectSingleton(Class<T> clazz,
                                                                                T object)

Registers a new singleton PlatformManagedObject for the provided interface and all its superinterfaces.

addPlatformManagedObjectList

public <T extends PlatformManagedObject> void addPlatformManagedObjectList(Class<T> clazz,
                                                                           List<T> objects)

Adds the provided list of PlatformManagedObject for the provided interface and all its superinterfaces.

isAllowedPlatformManagedObject

public boolean isAllowedPlatformManagedObject(PlatformManagedObject object)

noteThreadStart

public void noteThreadStart(Thread thread)

noteThreadFinish

public void noteThreadFinish(Thread thread)