The document discusses challenges and strategies for building composite user interfaces (UIs) for service-oriented systems. It addresses why distributed systems introduce challenges like unreliable networks, latency, security issues and more. It advocates using messaging to reduce coupling between services and address some of these challenges. The document provides strategies for structuring composite UIs, integrating legacy systems, handling queries, responses and messages to the UI, deployment considerations, managing contracts and dependencies between systems. It emphasizes keeping designs and implementations simple.

1. CompositeUI
forServiceOrientedSystems
DanielMarbach
@danielmarbach
bbvSoftwareServicesAG

2. De Composition
Why
How
Why
How

3. SystemApplication
Fancy1.0

4. SystemApplication
Fancy1.0

5. Thenetworkisreliable
Latencyisn’taproblem
Bandwidthisn’taproblem
Thenetworkissecure
Topologywon’tchange
Theadministratorwillknowwhattodo
Transportcostisn’taproblem
Thenetworkishomogeneous
Thesystemisatomic/monolithic
Thesystemisfinished
Businesslogiccanandshouldbecentralized

6. Thenetworkisreliable
var svc = new MyService();
var result = svc.Process(data);

7. Riskanalysis
Infrastructureandsoftwareredundancy
Reliablemessaging

8. Latencyisn’taproblem
Network
In-Memory
Serialization

9. Don’tcrossthenetwork
Takealldatayoumightneed
Minimizechit-chat

10. Bandwidthisn’taproblem
BigData
Congestion

11. Balanceeagerfetchvs.lazyloading
Balancebandwidthvs.latency
Separatenetworks

12. Thenetworkissecure
100%Safetyisnotpossible

13. Threatmodelanalysis
Balancecostsagainstrisks
Talkaboutit

14. Topologywon’tchange
Serverdown
Servermoved

15. Don’thard-code
Resilientprotocols
Discovery
ChaosMonkey

16. Theadministratorwill
knowwhattodo
Busfactor
Updates

17. Automate&Testdeployment
Designformultipleversionsrunning
concurrently
Allowpartofthesystemtobetaken
down

18. Transportcostisn’taproblem
Serialization
Hardware

19. Reducechit-chat
Infrastructureversusdevelopmentcosts

20. Thenetworkishomogeneous
.NET/Java
NoSQL,REST

21. Interopishard
Budgetforit

22. Thesystemisatomic/monolithic
Notscalable
SingleDB
Rippleeffects

23. Internalloosecoupling
Modularize
Designforscaleoutinadvance

24. Thesystemisfinished
Effort($/T) “Finished” Rewrite
Originaldate
“never”
finished

25. Designformaintenance
Designforupgrades
Versioningishard

26. Businesslogiccanand
shouldbecentralized

27. Logicisdistributed,livewithit
Groupbyfeature

28. BigBallofMudMonolithic

29. Coupling
XdependsonY

30. Afferent Efferent
whodependsonyou onwhoyoudepend

31. Platform Temporal Spatial

32. Platform
Interoperability
Usingplatformdependentprotocols
-Remoting
-EnterpriseServices
-DatasetsoverWebservices

33. Platform
XML/XSD,JSON,ProtocolBuffer
HTTP
WSDL
…

34. Temporal
XdependsonYandprocessingtimeofYdirectly
influencestheprocessingtimeofX.

35. Temporal
separatetheinter-servicecommunication
intimewithpub/sub

36. A
MakeCustomerPreferred()
B
Publishupdatedcustomerinfo
Storedata
Savecustomeras
preferred
PublishCustomermadepreferred

37. Spatial
Whenlocationnotavailablethesystemcannot
operate

38. Spatial
Introducelogicaldestinations
Loadbalancing
Routetologicaldestinations

39. Messaging
Reducescoupling
Addressessomeofthefallacies
Nosilverbullet

40. UseMessagingtotransferpacketsofdatafrequently,immediately,reliably,and
asynchronously,usingcustomizableformats.
Asynchronousmessagingisfundamentallyapragmaticreactiontotheproblemsof
distributedsystems.Sendingamessagedoesnotrequirebothsystemstobeupandready
atthesametime.Furthermore,thinkingaboutthecommunicationinanasynchronous
mannerforcesdeveloperstorecognizethatworkingwitharemoteapplicationisslower,
whichencouragesdesignofcomponentswithhighcohesion(lotsofworklocally)andlow
adhesion(selectiveworkremotely).

41. Messaging
Reducescoupling
(platform,temporal,afferentandefferent)
Addressessomeofthefallacies

42. Throughput
Load
RPC
Messaging

43. Receiver
Sends,andkeepsonworking
Sender
Id

44. Id
Receiver
Sender
Id
Outgoing
Incoming

45. DB
App
[HTTP]$$Order
Tx
Call1of3
Call2of3
Crash
Rollback
Where’stheorder!?

46. Infra
$$Order
Your
code
TXReceive
DB
Call1of3
Rollback
Call2of3
Rollback
Theorderisbackinthequeue
Invokes
DTC
Enlists
Q
Retry

47. DTCisatimebomb

48. Bus
$$Order
Your
code
Receive
DB
Call1of3
Rollback
Call2of3
Rollback
Theorderisbackinthequeue
Invokes
Q
Retry

49. Message
Payload(Body)
Metadata(Header)
%like%HTTP

50. Receiver
ReturnAddress Sometimeinthefuture
Sender
ReturnAddress

51. Receiver
Sometimeinthefuture
Sender
CorrelationID
MessageID

52. ReceiverSender
Receiver
Receiver

53. Ordering

54. MessagingBuy-in

55. Service
Function,WebService,ClassorDatabase
Setoftechnologies
Reusestrategy
Of-the-shelvesolution
WaytoalignITandbusiness

56. Business
capability
Data&
BusinessRules
Everything
iscontained
Nothingleft
over

57. Autonomous
ExplicitBoundaries
Contract&Schema
Policy Policy

58. DataOutsidevs.Inside

59. Outside Inside

60. UniqueID
(UUIDorwithhumanreadablewithversion)
OKtocache
Immutable
Validranges
Stable
Rulesforsendingmessages

61. UniqueID
(UUIDorwithhumanreadablewithversion)
OKtocache
Immutable
Validranges
Stable
Rulesforsendingmessages

62. Then Now

63. Command Event

64. Mashup

65. Bringingittogether

66. CompositeFrontEnd
Client/Server/Service

67. Portlet
Layout
Inter-portlet
communication
Shell
Single sign-on
UILogic
Agent
Host

68. Otherlegacysystems
UI
BusinessLogic
Adaptors
Serverlogic
Agent

69. Challengesyou’llface

70. Queries
Responses
MessagestoUI
Deployment
Contractsharing
Dependencies
Statusbars Dynamic

71. Queries
Don’tusemessaging
Usereadmodels
Databasesscalewellwhenreadonly
Justqueryit

72. Responses
NeverblocktheUI
EventAggregators
Forgetcallbacks,theysuck!

73. MessagestoUI
Doesn’tneedtobe1:1mapping
TaskbasedUI

74. Statusbars
Theynevertellthetruth
Tricktheuserwithsomeeducatedguesses
Useindeterminateprogressbars

75. Deployment
Keepitsimple
Automateit
Visualizeandmonitorit
Configurationcanbehard,designforit

76. Contractsharing
Favorloosecontractsoverinterfacesandclasses
Bepragmaticforcomposition
IT/OPSdefinesinterfaces,servicesimplementthem

77. Dependencies
SemanticVersioning
Nuget

78. Dynamic
Don’tgooverboardwithfancytechniques
Sometimeshard-wiringisjustfine

79. DanielMarbach
daniel.marbach@bbv.ch
twitter: @danielmarbach
blog: www.planetgeek.ch
www.bbv.ch/blog
OSSlead: Appccelerate/MSpec
usergroup: www.dotnet-zentral.ch