Nigel Daniels | Waratek Ltd.

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

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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

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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

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What will we cover?

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

• API overview• Demo

Introduction

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Java virtualization,an introduction

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Java virtualization, an introduction

Host Hardware

Hypervisor

Guest OS

Type 1 virtualization

Hardware

Host OS

Hypervisor

Guest OS

Type 2 virtualization

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Java virtualization, an introduction

Hypervisor

Host Hardware

Hypervisor(Virtual Machine Monitor)

Is it sensitive?

No

Emulate instruction

Yes

Trap x86instruction

Call

Guest OS

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Java virtualization, an introduction

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!

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Java virtualization, an introduction

Host JVM

Guest Application (JVC)

Hypervisor

JVM Hypervisor(Java Virtual Machine Monitor)

Is type virtualized?

No

Emulate type

accessYes

Exit transition

Call

With a type-1 virtual machine monitor for the JVM

All in pure Java!

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Key concepts

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Object != Object

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Key concepts, Object != Object

Host JVM

Hypervisor

DOM-0

JVC-1 JVC-2 JVC-3

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Key concepts, Object != Object

Host JVM

Hypervisor

DOM-0

JVC-1 JVC-2 JVC-3

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

java.util.HashMap

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Key concepts, Object != Object

Host JVM

Hypervisor

DOM-0

JVC-1 JVC-2 JVC-3

Real BCL

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

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Key concepts, Object != Object

Host JVM

Hypervisor

DOM-0

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′′′

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Exchanging objects

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Hypervisor

JVMM-1 JVMM-2 JVMM-3

JVMM-0

Key concepts, exchanging objects

Host JVM

DOM-0

JVC-1 JVC-2 JVC-3

RBCL

VBCL-A VBCL-B VBCL-C

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Hypervisor

JVMM-1 JVMM-2 JVMM-3

JVMM-0

Key concepts, exchanging objects

Host JVM

DOM-0

JVC-1 JVC-2 JVC-3

exit()

ObjectA

ObjectB

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Hypervisor

JVMM-1 JVMM-2 JVMM-3

JVMM-0

Key concepts, exchanging objects

Host JVM

DOM-0

JVC-1 JVC-2 JVC-3

entry()

ObjectC

ObjectB

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Hypervisor

JVMM-1 JVMM-2 JVMM-3

JVMM-0

Key concepts, exchanging objects

Host JVM

DOM-0

JVC-1 JVC-2 JVC-3

entry()

ObjectCObjectA

exit()

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DOM-0

Key concepts, exchanging objects

JVC-1 JVC-2

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Creating virtual environments

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Hypervisor

JVMM-1 JVMM-2 JVMM-3

JVMM-0

Key concepts, creating virtual environments

Host JVM

DOM-0

JVC-1 JVC-2 JVC-3

HostEnv-0

GuestEnv-1 GuestEnv-2 GuestEnv-3

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JVMM-1

Key concepts, creating virtual environments

JVC-1

GuestEnv-1

MonitorEnv

RuntimeSystemEnv

FileSystemEnvNetworkSystemEn

v

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Java Virtualization Interface API

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Java Virtualization Interface API

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Java Virtualization Interface API

Entry Point

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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

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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 ); }

JVI API – BootstrapEnv

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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; } … }

JVI API – BootstrapEnv

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DOM-0 typespace

JVC-1 typespace

VCL

RCL

Stub Class

Java Virtualization Interface API

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Java Virtualization Interface API

JVC Entry Point

NB. This may be renamed marshalling on release

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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

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DOM-0 typespace

JVC-1 typespace

Java Virtualization Interface API

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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 ); } }

JVI API – BootstrapEnv

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@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.

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DEMO

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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

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References

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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

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Thank You

nigel.daniels@waratek.com

Questions?