June 18-22, 2001 ECOOP 2001, Budapest, Hungary 1
A Bytecode Translator for Distributed Execution of “Legacy” Java Software
Michiaki Tatsubori*, Toshiyuki Sasaki*, Shigeru Chiba**, and Kozo
Itano*
* University of Tsukuba, Japan** Tokyo Institute of Technology, Japan
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 2
Developmentof Distributed Java Software
An example scenario “We have already got nice software.” “But we want to display GUI of the
software on a remote host.” Run GUI components on a remote host,
and run others on a local host
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 3
Two Approaches
Use X Window No need to edit a program
Rewrite a program by hand Using Java RMI or CORBA
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 4
X Window
Distribution by the Xlib Library Bad response time if GUI is complex
High communication overhead
“Draw a line”
“A mouse moved”
“A mouse-button pushed”
“A mouse-button released”
UserProgram
Xlib
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 5
Rewrite a Program by Hand
Good response time The programmer can tune the code. Low communication overheads.
UserProgram
Show an internal-window
A click in a window
ORBLibrary
UserProgram
Higher-level commands
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 6
Automation vs. Efficiency
X Window Fully automated, but Slow
By hand Many man-hours, though Fast
UserProgram
Xlib
UserProgram
GUI Module
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 7
Automation vs. Efficiency
X Window Decomposition at
the library layer
For better performance,complex decomposition isnecessary.
UserProgram
Xlib
UserProgram
GUI Module
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 8
Addistant – Our Solution
A Java program translator Translating a non-distributed program
to a distributed one Decomposing at anywhere
The user can specify the decomposition with a policy file.
UserProgram
GUI Module
Policy file
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 9
Addistant is a Practical Tool!
Bytecode translation by a class-loader Using Javassist[Chiba00]. No source code, no custom JVM.
Addistant can process real applications. It can migrate Swing components to a
remote host.Standard
library for rich GUI
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 10
Decomposition is Not Easy…
A simple proxy-master implementation NEVER works. Proxy-master – a typical
implementation technique for remote references
MasterProxyMethodInvocation
Network Communications
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 11
JavaRMI’s Way Doesn’t Work
To be remotely accessible, We must translate …
class WidgetImpl { …}
implements Widget {
interface Widget { …}
class WidgetProxy implements Widget { …}
If WidgetImpl is a system class,we cannot modify the class declaration!The JVM prohibits it.
If WidgetImpl is a system class,we cannot modify the class declaration!The JVM prohibits it.
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 12
In a Policy File of Addistant
Users choose one of four implementation techniques for each class. Those techniques modify code in
different ways. But they have different limitations in use.
Some techniques do not modify an original class, so they can be used for system classes.
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 13
Distributed Swing Application
A policy file<policy> <import proxy="rename" from="display"> [email protected] [email protected] .. </import> <import proxy="rename" from="application"> [email protected].[InputStream|OutputStream|..] [email protected].* </import> <import proxy="subclass"> [email protected].[AbstractCollection|..] </import> <import proxy="writeBackCopy"> array@- </import> <import proxy="replace" from="application"> user@- </import> <import proxy="copy"> - </import></policy>
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 14
“Rename” technique(e.g. for java.awt.Window)
It does not modify the original class. But local and remote references
cannot coexist on the same host.
Widget w = new Widget();w.show();
Widgetshow()
.. Show ..
Caller-side Class declaration
WidgetProxyshow()
.. Send ..
WidgetProxy w = new WidgetProxy();w.show();
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 15
“Subclass” technique(e.g. for java.util.Vector)
Local and remote references can coexist on the same host.
But the original class must not be final. If final, it must be modifiable.
Widget w = new Widget();w.show();
Widgetshow()
.. Show ..
Caller-side Class declaration
WidgetProxyshow()
.. Send ..
Local referenceRemote reference
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 16
Experiment: Response time
“Click” to “Pop-up a Window” Application Host
Sparc 440MHz GUI Host
PentiumII 500MHz Network
10Base-T Half 100Base-TX Full
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 17
Experiment: Response time
“Click” to “Pop-up a Window” Application Host
Sparc 440MHz GUI Host
PentiumII 500MHz Network
10Base-T Half 100Base-TX Full
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 18
Results of Experiments
Addistant showed good results. Response Time (sec.) 10base-t /
100base-tx
Transferred data size (kb)
(±0.1 sec.) X Window Rawt Addistant
1st pop-up 5.6 / 1.6 3.2 / 2.6 2.0 / 2.0
2nd pop-up 5.6 / 1.4 0.0 / 0.0 0.0 / 0.0
X Window Rawt Addistant
1st pop-up 3493.57 116.20 81.88
2nd pop-up 3438.96 10.95 0.06
IBM’s awt-compatiblelibrary for remote GUI
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Concluding Remarks
Addistant – an adapter of “legacy” Java programs for their distributed execution on multiple hosts A translator (automation) approach for
complex decomposition of a program A practical technology which can handles
Swing
Other Contribution A case-study of the usefulness of
Javassist[Chiba00]
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 20
Question or Suggestion?
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 21
System Classes
For implementing remote references, different way for a different class is used.Scopes of the required code modification are
different in each implementation Choosing implementation method avoiding
any modification of system classes “It’s no use kicking against bricks”
Declarative specification in a policy file “Replace”, “Rename”, “Subclass”, “Copy”
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 22
“Replace” Approach(e.g. user classes)
Replaces the master class declaration with a proxy version When the target class is modifiableOnly one version exists on a single JVM.
Widget w = new Widget();w.show();
Widgetshow()
Make it distributed
Widgetshow()
.. Show ..
.. Send ..
Replace all
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 23
“Copy” Approach(e.g. java.lang.String)
Does not create any proxy class, but transfers serialized objects to remote host at RMI Shallow copy
A Variation – “Write-back Copy” Approach For arrays
byte[] buf = …;istream.read(buf);
June 18-22, 2001 ECOOP 2001, Budapest, Hungary 25
Automating Development of Distributed Ver. of “Legacy” Soft
Less Developing Costs by AutomationReusing “Legacy”, Existing, Software
Ordinary Environments (Auto Remote GUI) X Window System 、 VNC 、 Rawt[IBM Haifa
98]
Ordinary Tools for (Semi-Auto) Distribution JavaRMI, ObjectSpace, Corba-compliant ORB… ”remotenew”[Nagaratnam 96] ,
JavaParty[Philippen 99] …、
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Distributed Execution of Software
For example,Separating GUI from application logic
Reduces administration costs, and Makes use of ubiquitous client-machines
“Zero Administration” “Thin Client”
