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Session-based Distributed Programming in Java
Raymond Hu
1
Session-based Distributed Programming in Java
Raymond Hu1, Nobuko Yoshida1 and Kohei Honda2
1. Imperial College London; 2. Queen Mary, Uni. of London
February 2008
Session-based Distributed Programming in Java
Raymond Hu
2
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
Session-based Distributed Programming in Java
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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
Session-based Distributed Programming in Java
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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)
• 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)
Theoretical Background
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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)
• 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.
Theoretical Background
Session-based Distributed Programming in Java
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Implementation of Session Types
• Singularity OS [FAHHHLL06]:– Restrictions on session features, not distributed.
Related Work
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Implementation of Session Types
• Singularity OS [FAHHHLL06]:– Restrictions on session features, not distributed.
• Multithreaded functional language design [VGR06]:– Not distributed, no actual implementation.
Related Work
Session-based Distributed Programming in Java
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Implementation of Session Types
• Singularity OS [FAHHHLL06]:– Restrictions on session features, not distributed.
• Multithreaded functional language design [VGR06]:– Not distributed, no actual implementation.
• Encodings of sess. types (e.g. Haskell [NT04], C++):– Demonstrate S.T. ideas, but not full implementations.
Related Work
Session-based Distributed Programming in Java
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Implementation of Session Types
• Singularity OS [FAHHHLL06]:– Restrictions on session features, not distributed.
• Multithreaded functional language design [VGR06]:– Not distributed, no actual implementation.
• 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)
1. Background and Related Work.
2. Worked Example: Session Programming in SJ.
3. The SJ Session Runtime.
4. Conclusion and Future Work.
Overview
Session-based Distributed Programming in Java
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An Online Ticket Ordering System
Worked Example: Session Programming in SJ
Session-based Distributed Programming in Java
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Protocol Specification (1)
begin
Worked Example: Session Programming in SJ
Session-based Distributed Programming in Java
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Protocol Specification (1)
begin.
!(String)
Worked Example: Session Programming in SJ
Session-based Distributed Programming in Java
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Protocol Specification (1)
begin.
!(String).
?(Double)
Worked Example: Session Programming in SJ
Session-based Distributed Programming in Java
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Protocol Specification (1)
begin.
!(String).
?(Double)
![
]*.
…
Worked Example: Session Programming in SJ
Session-based Distributed Programming in Java
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Protocol Specification (1)
begin.
?[
?(String).
!(Double)
]*.
…
begin.
!(String).
?(Double)
![
]*.
…
Worked Example: Session Programming in SJ
Session-based Distributed Programming in Java
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Protocol Specification (2)
…?{
}.
…
Worked Example: Session Programming in SJ
Session-based Distributed Programming in Java
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Protocol Specification (2)
…
ACCEPT:
… ,
REJECT:
…
?{
}.
…
Worked Example: Session Programming in SJ
Session-based Distributed Programming in Java
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Protocol Specification (3)
protocol p_as {
}
Worked Example: Session Programming in SJ
Session-based Distributed Programming in Java
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Protocol Specification (3)
protocol p_as {
}
begin.!(
)
Worked Example: Session Programming in SJ
Session-based Distributed Programming in Java
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Protocol Specification (3)
?(Address).!(Date)
protocol p_as {
}
begin.!(
)
Worked Example: Session Programming in SJ
Session-based Distributed Programming in Java
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Protocol Implementation (1)
protocol p_ca {begin.![!(String).?(Double)
]*.…
// Customer
SJSocket s_ca = SJSocketImpl.create(p_ca);
Worked Example: Session Programming in SJ
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Protocol Implementation (1)
protocol p_ca {begin.![!(String).?(Double)
]*.…
// Customer
SJSocket s_ca = SJSocketImpl.create(p_ca);
s_ca.request(Agency, port);
Worked Example: Session Programming in SJ
Session-based Distributed Programming in Java
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Protocol Implementation (1)
protocol p_ca {begin.![!(String).?(Double)
]*.…
// Customer
SJSocket s_ca = SJSocketImpl.create(p_ca);
s_ca.request(Agency, port);s_ca.outwhile(!decided) {
}
Worked Example: Session Programming in SJ
Session-based Distributed Programming in Java
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Protocol Implementation (1)
protocol p_ca {begin.![!(String).?(Double)
]*.…
// Customer
SJSocket s_ca = SJSocketImpl.create(p_ca);
s_ca.request(Agency, port);
s_ca.send(travDetails);
s_ca.outwhile(!decided) {
}
Worked Example: Session Programming in SJ
Session-based Distributed Programming in Java
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Protocol Implementation (1)
protocol p_ca {begin.![!(String).?(Double)
]*.…
// Customer
SJSocket s_ca = SJSocketImpl.create(p_ca);
s_ca.request(Agency, port);
s_ca.send(travDetails);
cost = (Double)s_ca.receive();
decided = …;
s_ca.outwhile(!decided) {
}
Worked Example: Session Programming in SJ
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Protocol Implementation (1)
protocol p_ca {begin.![!(String).?(Double)
]*.…
// Customer
SJSocket s_ca = SJSocketImpl.create(p_ca);
s_ca.request(Agency, port);
s_ca.send(travDetails);
decided = …;
s_ca.outwhile(!decided) {
}
cost = s_ca.receive();
Worked Example: Session Programming in SJ
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Protocol Implementation (2)
…!{ACCEPT:
… , // 1
REJECT:… // 2
}…
// Customer
s_ca.select(ACCEPT) {
… // 1
}
Worked Example: Session Programming in SJ
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Protocol Implementation (2)
…!{ACCEPT:
… , // 1
REJECT:… // 2
}…
// Customer
s_ca.select(ACCEPT) {
… // 1
}
if(cost < 100.00) {
}else {
}Worked Example: Session Programming in SJ
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Protocol Implementation (2)
…!{ACCEPT:
… , // 1
REJECT:… // 2
}…
// Customer
s_ca.select(ACCEPT) {
… // 1
}
s_ca.select(REJECT) {
… // 2
}
if(cost < 100.00) {
}else {
}Worked Example: Session Programming in SJ
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Protocol Implementation (3)
…
?{
ACCEPT:
… , // 1’
REJECT:
… // 2’
}
…
// Agency
…s_ac.branch() {
}
Worked Example: Session Programming in SJ
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Protocol Implementation (3)
…
?{
ACCEPT:
… , // 1’
REJECT:
… // 2’
}
…
// Agency
case ACCEPT: {
… // 1’
}
case REJECT: {
… // 2’
}
…s_ac.branch() {
}
Worked Example: Session Programming in SJ
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Putting Customer Togetherprotocol p_ca { … }
Worked Example: Session Programming in SJ
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Putting Customer Together
Worked Example: Session Programming in SJ
protocol p_ca { … }SJSocket s_ca = SJSocketImpl.create(p_ca);
Session-based Distributed Programming in Java
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Putting Customer Togetherprotocol p_ca { … }SJSocket s_ca = SJSocketImpl.create(p_ca);
s_ca.request(Agency, port);s_ca.outwhile(…) {
… }…
Worked Example: Session Programming in SJ
Session-based Distributed Programming in Java
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Putting Customer Togetherprotocol p_ca { … }SJSocket s_ca = SJSocketImpl.create(p_ca);
s_ca.request(Agency, port);s_ca.outwhile(…) {
… }…
try (s_ca) {
}
Worked Example: Session Programming in SJ
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Putting Customer Togetherprotocol p_ca { … }SJSocket s_ca = SJSocketImpl.create(p_ca);
s_ca.request(Agency, port);s_ca.outwhile(…) {
… }…
catch(SJIOException ioe) { … }
Worked Example: Session Programming in SJ
try (s_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(…) {
… }…
catch(SJIncompatibleSessionException ise) { … }catch(SJIOException ioe) { … }
Worked Example: Session Programming in SJ
try (s_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(…) {
… }…
catch(SJIncompatibleSessionException ise) { … }catch(SJIOException ioe) { … }finally {
… // Session socket ‘s_ca’ is closed.}
Worked Example: Session Programming in SJ
try (s_ca) {
}
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Overview (3)
1. Background and Related Work.
2. Worked Example: Session Programming in SJ
3. The SJ Session Runtime.
4. Conclusion and Future Work.
Overview
Session-based Distributed Programming in Java
Raymond Hu
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)
44The SJ Session Runtime
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Session Initiation (2)
C → A : Type of session expected by C.
| A → C : Type of session expected by A.
The SJ Session Runtime
Session-based Distributed Programming in Java
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Basic Message Passing
46The SJ Session Runtime
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Sessions over TCP (2)
• Map session operations to Socket communications.– Distributed communication.– Preserve asynchrony.
Interesting case is delegation.
The SJ Session Runtime
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“Lost Messages” (1)
The SJ Session Runtime
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“Lost Messages” (2)
The SJ Session Runtime
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Sessions over TCP (3)
• Map session operations to Socket communications.– Distributed communication.– Preserve asynchrony.
Interesting case is delegation.
Possible designs: Indefinite forwarding (cf. MobileIP).
The SJ Session Runtime
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Sessions over TCP (3)
• Map session operations to Socket communications.– Distributed communication.– Preserve asynchrony.
Interesting case is delegation.
Possible designs:× Indefinite forwarding (cf. MobileIP). “Lost message” resending.
The SJ Session Runtime
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Sessions over TCP (3)
• Map session operations to Socket communications.– Distributed communication.– Preserve asynchrony.
Interesting case is delegation.
Possible designs:× Indefinite forwarding (cf. MobileIP). “Lost message” resending. “Lost message” forwarding.
The SJ Session Runtime
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Session Delegation (1)
The SJ Session Runtime
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Session Delegation (2)
1. S: Create server socket on p.
The SJ Session Runtime
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Session Delegation (3)
1. S: Create server socket on p.
2. S → A: p
The SJ Session Runtime
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Session Delegation (4)
1. S: Create server socket on p.
2. S → A: p
3. A → C: S, p, ST(A)
The SJ Session Runtime
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Forwarding
4. A → S: “Lost messages” forwarded.
5. C: Connect to S:p
The SJ Session Runtime
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Resending
4. C: Connect to S:p
5. C → S: “Lost messages” according to Session Types.
The SJ Session Runtime
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Session Delegation (5)• What if A has finished her side of the session?
59The SJ Session Runtime
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Session Delegation (5)• What if A has finished her side of the session?• What if A is sending a session?
60The SJ Session Runtime
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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?
61The SJ Session Runtime
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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.
62The SJ Session Runtime
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Overview (4)
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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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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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.• Runtime architecture for session abstraction.
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.• Runtime architecture for session abstraction.• Asynchronous communication and distribution.
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.• Runtime architecture for session abstraction.• Asynchronous communication and distribution.• Session subtyping, interleaving, exceptions/failure.
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.• 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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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.• 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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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.• 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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Preliminary Results (1)
• 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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Preliminary Results (2)
Results
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