session-based distributed programming in java raymond hu 1 session-based distributed programming in...

Session-based Distributed Programming in Java

Raymond Hu

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Raymond Hu1, Nobuko Yoshida1 and Kohei Honda2

1. Imperial College London; 2. Queen Mary, Uni. of London

February 2008


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Overview (1)

1. Background and Related Work.

2. Worked Example: Session Programming in SJ.

3. The SJ Session Runtime.

4. Conclusion and Future Work.

Overview


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Session Types

• Type systems for process calculi:– Takeuchi et al. An Interaction-based Language and its Typing System. (1994)– Honda et al. Language Primitives and Type Discipline for Structured Comm… (1998)– Gay and Hole. Subtyping for Session Types in the Pi Calculus. (1999)– Hole and Gay. Bounded Polymorphism in Session Types. (2003)

Theoretical Background


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Session Types


• Session types for object calculi:– Dezani-Ciancaglini et al. A distributed Object-oriented Language with Session... (2005)– Dezani-Ciancaglini et al. Session Types for Object-oriented Languages. (2006)– Dezani-Ciancaglini et al. Bounded Session Types for Object-oriented Languages. (2007)– Coppo et al. Asynchronous Session Types and Progress for Object-oriented... (2007)



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Session Types


• Session types for object calculi:– Dezani-Ciancaglini et al. A distributed Object-oriented Language with Session... (2005)– Dezani-Ciancaglini et al. Session Types for Object-oriented Languages. (2006)– Dezani-Ciancaglini et al. Bounded Session Types for Object-oriented Languages. (2007)– Coppo et al. Asynchronous Session Types and Progress for Object-oriented... (2007)

Implementation of a practical and distributed language.



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Implementation of Session Types

• Singularity OS [FAHHHLL06]:– Restrictions on session features, not distributed.

Related Work


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• Multithreaded functional language design [VGR06]:– Not distributed, no actual implementation.

Related Work


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• Encodings of sess. types (e.g. Haskell [NT04], C++):– Demonstrate S.T. ideas, but not full implementations.

Related Work


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• Encodings of sess. types (e.g. Haskell [NT04], C++):– Demonstrate S.T. ideas, but not full implementations.

Why use “untyped” sockets if we can use sessions?

Related Work


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Overview (2)





Overview


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An Online Ticket Ordering System

Worked Example: Session Programming in SJ


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Protocol Specification (1)

begin



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begin.

!(String)



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begin.

!(String).

?(Double)



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begin.

!(String).

?(Double)

![

]*.

…



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begin.

?[

?(String).

!(Double)

]*.

…

begin.

!(String).

?(Double)

![

]*.

…



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…?{

}.

…



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…

ACCEPT:

… ,

REJECT:

…

?{

}.

…



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protocol p_as {

}



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protocol p_as {

}

begin.!(

)



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?(Address).!(Date)

protocol p_as {

}

begin.!(

)



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Protocol Implementation (1)

protocol p_ca {begin.![!(String).?(Double)

]*.…

// Customer

SJSocket s_ca = SJSocketImpl.create(p_ca);



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]*.…

// Customer


s_ca.request(Agency, port);



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]*.…

// Customer


s_ca.request(Agency, port);s_ca.outwhile(!decided) {

}



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]*.…

// Customer



s_ca.send(travDetails);

s_ca.outwhile(!decided) {

}



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]*.…

// Customer




cost = (Double)s_ca.receive();

decided = …;


}



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]*.…

// Customer




decided = …;


}

cost = s_ca.receive();



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…!{ACCEPT:

… , // 1

REJECT:… // 2

}…

// Customer

s_ca.select(ACCEPT) {

… // 1

}



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…!{ACCEPT:

… , // 1

REJECT:… // 2

}…

// Customer


… // 1

}

if(cost < 100.00) {

}else {

}Worked Example: Session Programming in SJ


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…!{ACCEPT:

… , // 1

REJECT:… // 2

}…

// Customer


… // 1

}

s_ca.select(REJECT) {

… // 2

}

if(cost < 100.00) {

}else {

}Worked Example: Session Programming in SJ


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…

?{

ACCEPT:

… , // 1’

REJECT:

… // 2’

}

…

// Agency

…s_ac.branch() {

}



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…

?{

ACCEPT:

… , // 1’

REJECT:

… // 2’

}

…

// Agency

case ACCEPT: {

… // 1’

}

case REJECT: {

… // 2’

}

…s_ac.branch() {

}



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Putting Customer Togetherprotocol p_ca { … }



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Putting Customer Together


protocol p_ca { … }SJSocket s_ca = SJSocketImpl.create(p_ca);


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Putting Customer Togetherprotocol p_ca { … }SJSocket s_ca = SJSocketImpl.create(p_ca);

s_ca.request(Agency, port);s_ca.outwhile(…) {

… }…



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… }…

try (s_ca) {

}



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… }…

catch(SJIOException ioe) { … }


try (s_ca) {

}


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… }…

catch(SJIncompatibleSessionException ise) { … }catch(SJIOException ioe) { … }


try (s_ca) {

}


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… }…

catch(SJIncompatibleSessionException ise) { … }catch(SJIOException ioe) { … }finally {

… // Session socket ‘s_ca’ is closed.}


try (s_ca) {

}


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Overview (3)


2. Worked Example: Session Programming in SJ



Overview


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General Framework

41The SJ Session Runtime


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Session Runtime Architecture

42


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Sessions over TCP (1)

• Map session operations to Socket communications.– Distributed interaction.– Preserve asynchrony.

The SJ Session Runtime


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Session Initiation (1)



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Session Initiation (2)

C → A : Type of session expected by C.

| A → C : Type of session expected by A.



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Basic Message Passing



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• Map session operations to Socket communications.– Distributed communication.– Preserve asynchrony.

Interesting case is delegation.



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“Lost Messages” (1)



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“Lost Messages” (2)



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Possible designs: Indefinite forwarding (cf. MobileIP).



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Possible designs:× Indefinite forwarding (cf. MobileIP). “Lost message” resending.



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Possible designs:× Indefinite forwarding (cf. MobileIP). “Lost message” resending. “Lost message” forwarding.



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Session Delegation (1)



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1. S: Create server socket on p.



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2. S → A: p



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2. S → A: p

3. A → C: S, p, ST(A)



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Forwarding

4. A → S: “Lost messages” forwarded.

5. C: Connect to S:p



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Resending

4. C: Connect to S:p

5. C → S: “Lost messages” according to Session Types.



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Session Delegation (5)• What if A has finished her side of the session?



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Session Delegation (5)• What if A has finished her side of the session?• What if A is sending a session?



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Session Delegation (5)• What if A has finished her side of the session?• What if A is sending a session?• What if A is delegating the session at the same time?



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Session Delegation (5)• What if A has finished her side of the session?• What if A is sending a session?• What if A is delegating the session at the same time?• Asynchronous session-send.



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Overview (4)





Overview


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Conclusion http://www.doc.ic.ac.uk/~rh105/sessionj.html

Conclusion


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Conclusion http://www.doc.ic.ac.uk/~rh105/sessionj.html• Integration of session type theory and O-O for

practical, type-safe session-based programming.

Conclusion


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practical, type-safe session-based programming.• Runtime architecture for session abstraction.

Conclusion


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practical, type-safe session-based programming.• Runtime architecture for session abstraction.• Asynchronous communication and distribution.

Conclusion


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practical, type-safe session-based programming.• Runtime architecture for session abstraction.• Asynchronous communication and distribution.• Session subtyping, interleaving, exceptions/failure.

Conclusion


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practical, type-safe session-based programming.• Runtime architecture for session abstraction.• Asynchronous communication and distribution.• Session subtyping, interleaving, exceptions/failure.• Combination of static and dynamic session types.

Conclusion


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practical, type-safe session-based programming.• Runtime architecture for session abstraction.• Asynchronous communication and distribution.• Session subtyping, interleaving, exceptions/failure.• Combination of static and dynamic session types.• Eager class downloading and verification.

Conclusion


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practical, type-safe session-based programming.• Runtime architecture for session abstraction.• Asynchronous communication and distribution.• Session subtyping, interleaving, exceptions/failure.• Combination of static and dynamic session types.• Eager class downloading and verification.• Low overhead.

Conclusion


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Future Work• Write more code!

Future Work


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Future Work• Write more code!• Usability improvements (syntax, features, ...).

Future Work


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Future Work• Write more code!• Usability improvements (syntax, features, ...).• Communication optimisations.

Future Work


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Future Work• Write more code!• Usability improvements (syntax, features, ...).• Communication optimisations.• Sessions over alternative transports.

Future Work


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Future Work• Write more code!• Usability improvements (syntax, features, ...).• Communication optimisations.• Sessions over alternative transports.• Multiparty sessions.

Future Work


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Future Work• Write more code!• Usability improvements (syntax, features, ...).• Communication optimisations.• Sessions over alternative transports.• Multiparty sessions.• Session exceptions.

Future Work


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Future Work• Write more code!• Usability improvements (syntax, features, ...).• Communication optimisations.• Sessions over alternative transports.• Multiparty sessions.• Session exceptions.• Automatic session implementation generation.

Future Work


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Future Work• Write more code!• Usability improvements (syntax, features, ...).• Communication optimisations.• Sessions over alternative transports.• Multiparty sessions.• Session exceptions.• Automatic session implementation generation.• Further integration of sessions and objects.

Future Work


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Future Work• Write more code!• Usability improvements (syntax, features, ...).• Communication optimisations.• Sessions over alternative transports.• Multiparty sessions.• Session exceptions.• Automatic session implementation generation.• Further integration of sessions and objects.

Future Work


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Preliminary Results (1)

• For simple benchmark experiment, implemented:

begin . ![ ?( MyObject ) ]* . end

Results


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• For simple benchmark experiment, implemented:

begin . ![ ?( MyObject ) ]* . end

• Using:– SJFSocket and SJRSocket– java.net.Socket– RMI: MyObject remoteMeth(Boolean bool)

Results


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Results

session-based distributed programming in java raymond hu 1 session-based distributed programming in...

Documents

session programming

session features

bounded session types

distributed programming

asynchronous session

sj session runtime

session types type systems

distributed language