A Reference Architecture for
Self-organizing Service-oriented Computing
Lei Liu,
Stefan Thanheiser, Hartmut Schmeck
Institute for Applied Informatics und Formal Description Methods (AIFB)
Karlsruhe Institute of Technology (KIT)
International Conference on Architecture of Computing Systems
(ARCS 2008)
Feb. 2008, Dresden
Germany
Agenda
Motivation
Key Design Challenges for self-organising SOA
Reference Architecture
Rationale
Motivation
Today
–
Service-orientation
as design paradigm
Encapsulating
business capabilities with reusable
Web service interfaces
Increasing adoption in enterprise
Challenge
– managing Service-oriented Architecture (SOA) as large
scale distributed application
Complexity
in SOA
Existing centralized
management solutions insufficient
Idea
– hybrid management approach by embedding controlled
self-organisation in SOA
Decentralized Self-organisation
via multi-level Observer/Controller
Architecture of Organic Computing
Centralized external control
via high-level policies
Database
Se
rvic
e
Pr
ovi
d
e
r
Mainframe
SQL-DB
Se
rvic
e
Co
n
su
m
e
r
UNIX-Server
Windows
Server
Linux-
Java
-Server
Document
Management
System
httpd
1
Application
Server
httpd
2
.NET
Key Design Challenges for Self-organising SOA
Service-oriented
Architecture
Service
autonomy
Dependency
Decentraliza-tion and
Distribution
Dynamism
Heterogeneity
and
Interoperability
Scalability
Transparency
SOA
reduces
IT complexity
Abstraction
of technical
details
Consistent
representation of
business logic and data
→
Better structured IT
infrastructure
SOA
complicates
decentralized management
Increasing
integration
Distributed
application
across organisations
Design challenges
Related Work
Reference architectures for Service-oriented computing
Service-oriented Solution Stack (S3) (Arsanjani et al., 2007)
Similar approaches: Integrated Service-oriented Architecture (iSOA) (KIM,
2005) or Extended Service-oriented Architecture (eSOA) (Papazoglou, 2005)
Addressing abstractly the management/governance aspect
Reference architectures for Self-organisation
Viable System Model (VSM) (Beer, 1959)
Recursive generic model for self-organisation
3 interacting aspects:
operation
,
control
, and
environment
5 interacting subsystems with predefined capabilities
MAPE control loop of Autonomic Computing (IBM, 2005)
Generic Observer/Controller (O/C) Architecture of Organic Computing
Reference Architecture
Goal – an architectural blueprint for designing SOA with:
Decentralized self-organisation within SOA component
Collaboration between self-organising SOA components
Control over SOA components with high-level policies
Hiding system complexity
Our Approach
Local - Managing Element
Establishing self-organisation in SOA component
Global - Management Overlay
Organising managing elements into overlay
Separation between
management-centric
and
service-centric
communication
Enabling collaboration between managing elements
Reference Architecture – Managing Element (I)
Abstract architectural pattern for Managing Element with controlled
self-organisation
Service Component
: e.g. a Web service or a Web server
Environment
: the set of (related)
managing elements
Self-organisation
Local Coordinator
Local Control
Global Coordinator
Global Control
Control
Global Control
External high-level policies
En
v
iro
nm
ent
Service Component
Managing Element
Monitor
Control
Global Control
Local
Coordinator
Global Coordinator
Local Control
Local Operative
Unit(s)
External
Policies
A
bst
rac
t
Con
crete
Reference Architecture – Managing Element (II)
The architecture pattern for Managing Element covers
Operational
aspect of local
service component
Control
aspect, in particular by external
policies
Environment
aspect
Aspect-separation allows
Clear
and modular
design of
self-organizing component
Increased
reusability
Address the design challenges
Service autonomy
Transparency
En
v
iro
nm
ent
Service Component
Monitor
Control
Global Control
Local
Coordinator
Global Coordinator
Local Control
Local Operative
Unit(s)
External
Policies
Managing Element
Reference Architecture – Management Overlay (I)
Management Overlay
Structure Mapping
1-1 Management
Reference Architecture – Management Overlay (II)
Separation
between
management-centric
and
service-centric
communication
Service-oriented
management overlay
Organising managing elements with service-orientation
Managing elements expose management capabilities via Web services
interface
Managing elements communicate via Web services
Flexible management overlay
Internal changes of managing elements do not effect the management
overlay
Including additional component(s) into overlay, e.g. services providing
decision support in case of conflicts
Dynamic overlay wrt. changes in the underlying SOA layer
Rationale – Our Approach for Decentralized Management
Advantages
Combining
local
and
global
context
Enabling
flexible
design of management overlay
Robust
management approach vs. centralized management
Remaining
controllable
via external policies
Disadvantages
More
communication
and
coordination
efforts
(Possibly)
suboptimal
decision due to limited view
Trade-off
between
centralized but restricted
control
and
decentralized but robust
control
Summary & Outlook
Analysed existing reference architectures for SOC and Self-organisation
Proposed a reference architecture for self-organising SOA
Management Overlay for global
context
Managing Element for local
management
Characteristics of our reference architecture
Generic
and technology independent approach
Flexible
and agile
architecture wrt. underlying SOA layer
Outlook
Refinement of the reference architecture
Proof-of-concept implementation in an SOA simulation environment
Thank you for your attention!
Questions?
For any question please feel free to contact
Lei Liu
Karlsruhe Institute of Technology (KIT)
University of Karlsruhe
Institute of Applied Informatics and Formal Description Methods (AIFB)
Email: [email protected]
Viable System Model (VSM)
System 2
A
B
System
1 (A)
System
1 (B)
System 3
System 4
System 5
Environment
Reference Architecture – Managing Element (III)
Local Opertional Unit Local Coordinatior Local Control Global Coordinator Global Control Environ-mentReference Architecture – Managing Element (IV)
Local Opertional Unit Local Coordinatior Local Control Global Coordinator Global Control Environ-mentReference Architecture – Managing Element (V)
Local Opertional Unit Local Coordinatior Local Control Global Coordinator Global Control Environ-ment