Want to do the impossible with Java? Lets do it!

Nigel Daniels | Waratek Ltd.

Want to do the impossible with Java? Let‘s do it!

Nigel Daniels• Wide range of tech roles including robotics,

process control, network management, 3D visualization, media and enterprise software.

• 8 years with IBM developing, delivering and managing WebSphere related products.

• Now freelance consulting on software product management and delivery.

• Consulting Product Manager with Waratek for 1½ years.

Introduction

Java Virtualization Interface

• A pure-Java hypervisor inside the JVM.• Makes JVM multitenant, creates Java Virtual

Containers (JVCs).• Simple example:

• chroot for a JVC, written in pure-Java.• Complex example:

• Virtualise webapps running on Apache Tomcat et al.• Currently on Waratek’s CloudVM for Java.• V 1.0 – OSS License, includes the virtualization

driver for Apache Tomcat.

Introduction

What will we cover?

• Java virtualization, an introduction• Key concepts• Object != Object• Exchanging objects• Creating virtual environments

• API overview• Demo

Introduction

Java virtualization,an introduction

Java virtualization, an introduction

Host Hardware

Hypervisor

Guest OS

Type 1 virtualization

Hardware

Host OS

Hypervisor

Guest OS

Type 2 virtualization

Hypervisor

Host Hardware

Hypervisor(Virtual Machine Monitor)

Is it sensitive?

Emulate instruction

Trap x86instruction

Guest OS

Trap-and-emulating x86 instructions doesn’t work for Java, all JVM instructions are non-sensitive.

But what about a call like:

java.lang.System.exit(int)

JavaEE and every other Java application framework uses co-operative multi-tenancy…

So how do we provide fully isolated virtualization for Java?

but the last time co-operative multi-tenancy was used was in Windows 3.1 and Mac OS 9 in the 1990’s!

Host JVM

Guest Application (JVC)

Hypervisor

JVM Hypervisor(Java Virtual Machine Monitor)

Is type virtualized?

Emulate type

accessYes

Exit transition

With a type-1 virtual machine monitor for the JVM

All in pure Java!

Key concepts

Object != Object

Key concepts, Object != Object

Host JVM

Hypervisor

JVC-1 JVC-2 JVC-3

Host JVM

Hypervisor

JVC-1 JVC-2 JVC-3

java.util.HashMap java.util.HashMap java.util.HashMap

java.util.HashMap

Host JVM

Hypervisor

JVC-1 JVC-2 JVC-3

Real BCL

Virtual BCL-A Virtual BCL-B Virtual BCL-C

Host JVM

Hypervisor

JVC-1 JVC-2 JVC-3

Real BCL

Virtual BCL-A Virtual BCL-B Virtual BCL-C

define()

java.util.HashMap

JIT emitted byte[]

HashMap

define()

HashMap′

define()

HashMap′′

define()

HashMap′′′

Exchanging objects

Hypervisor

JVMM-1 JVMM-2 JVMM-3

JVMM-0

Key concepts, exchanging objects

Host JVM

JVC-1 JVC-2 JVC-3

VBCL-A VBCL-B VBCL-C

Hypervisor

JVMM-0

Host JVM

JVC-1 JVC-2 JVC-3

exit()

ObjectA

ObjectB

Hypervisor

JVMM-0

Host JVM

JVC-1 JVC-2 JVC-3

entry()

ObjectC

ObjectB

Hypervisor

JVMM-0

Host JVM

JVC-1 JVC-2 JVC-3

entry()

ObjectCObjectA

exit()

JVC-1 JVC-2

Creating virtual environments

Hypervisor

JVMM-0

Key concepts, creating virtual environments

Host JVM

JVC-1 JVC-2 JVC-3

HostEnv-0

GuestEnv-1 GuestEnv-2 GuestEnv-3

JVMM-1

Key concepts, creating virtual environments

GuestEnv-1

MonitorEnv

RuntimeSystemEnv

FileSystemEnvNetworkSystemEn

Java Virtualization Interface API

Entry Point

package org.apache.catalina.startup;…public class BootstrapEnv extends HostEnv

When the hypervisor starts a particular sequence is used to determine if a driver is to be loaded:

1. Is the class provided an instance of HostEnv?2. Else append “Env” to the fully qualified class name. Is there a

matching class?3. Else call the standard main entry point for the class.

The JVI drivers entry point replaces the standard call to public static void main (String[] args).

JVI API – BootstrapEnv

public void start( String[] args, Class mainClass ) { // Step 1) tell the world we're loading… … // Step 2) load our managed entry transitions. … // Step 3) start Tomcat proper super.start( args, mainClass ); }

public ClassLoaderEnv virtualize( final ClassLoader cl ) { // Load our privileged types … // Is this class loader a child of a virtualized // class loader? … else if( cl.getClass().getName().equals( "org.apache.catalina.loader.WebappClassLoader")) { // This is a webapp class loader, virtualise this! … tomcat_driver.ServletMonitorEnv me = new tomcat_driver.ServletMonitorEnv(this, name, cl); ClassLoaderEnv webappClassLoaderEnv = me.startJVC(); … return webappClassLoaderEnv; } … }

DOM-0 typespace

JVC-1 typespace

Stub Class

JVC Entry Point

NB. This may be renamed marshalling on release

public ClassLoaderEnv startJVC() { // Load our managed exit transitions … // Start the JVC super.start(); // Setup the virtualized web app class loader environment … return webappClassLoaderEnv; }

JVI API – MonitorEnv

DOM-0 typespace

JVC-1 typespace

public ClassLoaderEnv virtualize( final ClassLoader cl ) { // Load our privileged types if ( privTypes == null &&cl.getClass().getName().equals("org.apache.catalina.loader.StandardClassLoader”)) { privTypes = new TypeSet( cl ); try { privTypes.loadPackages( new String[]{ "javax.servlet.", "javax.el." }, true, new String[] { "javax.servlet.jsp.el.ImplicitObjectELResolver$Scope”}, ); privTypes.loadClass( "org.apache.tomcat.InstanceManager" ); privTypes.loadClass( "java.io.Writer" ); … // that’s all the classes, so seal it now. privTypes.seal(); } catch( ClassNotFoundException e ) { throw new EnvironmentError( e ); } }

@MemberExit(type={ "javax/servlet/ServletRequest", "javax/servlet/ServletRequestWrapper" }, name="getLocale", descriptor="()Ljava/util/Locale;", conversion={ "java.util.Locale" } ) public static Locale getLocaleX( ServletRequest req ) { return req.getLocale(); }

Java Virtualization Interface API – Exit/Entry

As the hypervisor loads the JVI driver the following sequence takes place for each member:

1. Is the member a privileged type (in the intersection)?2. Is there a matching description of the member as a Member

Entry or Exit?3. Failing ether of these throw an error while loading the driver.

Here we can completely override the function without sub-classing, this gives us true polymorphism! We can make our Local anywhere.

What have we covered?• Java virtualization is type 1 virtualization, and

is pure Java.• This requires typespace virtualization.• Virtual machine monitors marshal the types

and handle the transitions (unless the type is privileged).

• The API allows us entry points into the VMMs.• We can now extend and control the entire JVM

image!

Summary

References

Virtualisation references:https://en.wikipedia.org/wiki/Virtual_machine_monitorhttps://en.wikipedia.org/wiki/Popek_and_Goldberg_virtualization_requirementshttps://en.wikipedia.org/wiki/X86_virtualization

JVI an Introduction (Part I)http://www.waratek.com/blog/june-2013/open-source-api-for-java-virtualization

General information about the Waratek CloudVM:http://www.waratek.com

Elasticat (JVI implemented for TomCat):http://www.waratek.com/product/elasticat

JVI source code and Java doc (coming soon):https://github.com/waratek

Thank You

nigel.daniels@waratek.com

Questions?

Want to do the impossible with Java? Lets do it!

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