A Software Architecture for Translucent Replication

1
A Software Architecture for Translucent
Replication

• Etienne Antoniutti Di MuroUniversità degli Studi
  di Trieste, Italy
• eantoniutti_at_units.it

29th November, 2005
2nd Middleware Doctoral Symposium _at_
Middleware 2005 Conference, Grenoble, France
2
Directions
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro

• Arjuna Technologies Ltd.Newcastle upon Tyne, UK
• Stuart Wheater (co-supervisor )

• Università degli Studi di Trieste
• Etienne Antoniutti Di Muro
• Prof. Alberto Bartoli (supervisor )

2nd Middleware Doctoral Symposium _at_ Middleware
2005 Conference,Grenoble, France 29th November
2005
29th November, 2005
2nd Middleware Doctoral Symposium _at_ Middleware
2005 Conference, Grenoble, France
2/23
3
Food for thought
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro

• gt Background and motivations
• gt Middleware transparency, crisis and paradox
• lt interlude clustering and replication /gt
• gt Dependability vs. performance
• gt Goal Address dependability and performance
  conflicts
• gt Proposal Translucent replication
• gt top-down and bottom-up translucency models
• gt application requirements
• gt Evaluation Translucent replication in a real
  case scenario
• lt interlude JMS clustering /gt
• gt JMS translucent replication
• gt Summary and Conclusions

29th November, 2005
2nd Middleware Doctoral Symposium _at_ Middleware
2005 Conference, Grenoble, France
3/23
4
Background and motivations
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro

• Middleware born TRANPARENT and HOMOGENEOUS

• to provide a common high-level environment to
  the components of a distributed system
• to isolate applications form underlying hw/sw
  changes

29th November, 2005 2nd
Middleware Doctoral Symposium _at_ Middleware 2005
Conference, Grenoble, France
4/23
5
Background and motivations
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro

• Middleware grown MONOLITHIC and HETEROGENEOUS
• to achieve transparency
• to accommodate application complexity,
  distribution models, (COTS) component reuse
• Middleware requires a partial redesign to match
  the exact application requirements the
  middleware crisis
• Middleware faces an interoperability problem
  coming from middleware itself the middleware
  paradox

29th November, 2005
2nd Middleware Doctoral Symposium _at_ Middleware
2005 Conference, Grenoble, France
5/23
6
lt interlude clustering and replication gt
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro
Service

• Clustering exploiting services using multiple
  physical machines w/ external appearance of
  one single highly capable server
• performance
• Replication having a service replicated across
  multiple nodes ensures that another instance
  of the service exists if one replica crashes
• service dependability, i.e. availability and
  reliability

29th November, 2005
2nd Middleware Doctoral Symposium _at_ Middleware
2005 Conference, Grenoble, France
6/23
7
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro

• Clustering and Replication a common
  requirement is replication transparency neither
  clients nor applications should have to be aware
  of multiple physical data replicas
• Example
• ADAPT (Middleware Technologies for Adaptive and
  Composable Distributed Components). EU contract
  no. IST-2001-37126 (2005)
• no interaction between the replicated beans and
  the replication layer across the
  application/middleware boundary

Application/middleware boundary
29th November, 2005
2nd Middleware Doctoral Symposium _at_ Middleware
2005 Conference, Grenoble, France
7/23
8
lt interlude clustering and replication /gt
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro

• gt Example
• A Replication Framework for Program-to-Program
  Interaction across Unreliable Networks and its
  Implementation in a Servlet Container (2004)
• no interaction between the replicated web
  service and the replication layer across the
  application/middleware boundary

application/middleware boundary
29th November, 2005
2nd Middleware Doctoral Symposium _at_ Middleware
2005 Conference, Grenoble, France
8/23
9
Background and motivations
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro

• Dependability and performance conflicts
• dependability long-standing desirable property
• efficient replication remains challenging
• Maintaining high performance figures while
  ensuring strong consistency presents a tough
  contest
• Replication transparency leads to
  under-utilization of resources with resulting
  poor application performance

29th November, 2005
2nd Middleware Doctoral Symposium _at_ Middleware
2005 Conference, Grenoble, France
9/23
10
Goal
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro

• Address system dependability and performance
  conflicts introducing Middleware Translucency
• New software architectural model
• Middleware layers interfaces and interactions
  are exposed to the system designers
• transparently to the application that want it
• with the desired level of granularity to the
  applications that need it
• Dependability and performance conflicts have to
  become trade-offs
• Trade-offs offer sets of solutions for the
  dependability/performance conflicts in the
  application design space

29th November, 2005 2nd
Middleware Doctoral Symposium _at_ Middleware 2005
Conference, Grenoble, France
10/23
11
Goal
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro

• Novel translucency models
• top-down upper layers provide information to
  lower layers about how they want their requests
  to be satisfied
• bottom-up lower layers provide information to
  upper layers about how they are performing their
  work and the computational environment, so that
  upper layers can adapt their behavior
• Strong cross-layer interaction
• Dynamical adaptability of middleware layers
• Middleware high configurability to application
  requirements

29th November, 2005 2nd
Middleware Doctoral Symposium _at_ Middleware 2005
Conference, Grenoble, France
11/23
12
Proposal
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro

• Translucent Replication
• novel architecture for replicated
  infrastructures
• decomposition of system level clustering
  requirements into lower level functional
  requirements
• layered services realize functional requirements
  

distributed application(s)
REPLICATIONMIDDLEWARE
operating system hardware
29th November, 2005
2nd Middleware Doctoral Symposium _at_ Middleware
2005 Conference, Grenoble, France
12/23
13
Proposal
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro
lt top-down translucency model components
lt bottom-up translucency model components
lt replicated data path

• Translucent Replication
• Top-down and bottom-up model

lt top-down translucency model information path
lt bottom-up translucency model information path
Single Replica
application/middleware boundary
API
Semantic Rules
REPLICATIONMIDDLEWARE
gt
(Custom)Sensors
29th November, 2005 2nd
Middleware Doctoral Symposium _at_ Middleware 2005
Conference, Grenoble, France
13/23
14
Proposal
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro

• Translucent Replication reasoning on data
  semantics
• generic way to implement smart replication
  middleware
• provides the finest level of granularity for
  data handling
• deals with replication of a wide range of
  entities
• i.e. raw and plain data / objects / components
• no need to develop specific different patterns
• Application requirements
• formal description of operation and data
  semantics
• messages sent to the middleware in a clear an
  fixed format
• Designers / Programmers
• define rules to enable data semantics access
• define sensors to monitor resources for
  application-specific adaptation

29th November, 2005 2nd
Middleware Doctoral Symposium _at_ Middleware 2005
Conference, Grenoble, France
14/23
15
Evaluation
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro

• Translucent Replication model evaluation
  tricky
• put in numbers the advantages of solutions based
  on data semantics
• flexibility and adaptability of a middleware
  architecture to specific application
  dependability solutions
• different levels of granularity explosion of
  the number of possible tunable parameters
• solutions in a multidimensional space
• providing translucent methodologies to
  application design is a trade-off itself
• Model application evaluation
• Real case scenario evaluation

29th November, 2005
2nd Middleware Doctoral Symposium _at_ Middleware
2005 Conference, Grenoble, France
15/23
16
Evaluation
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro
lt opaque data class
lt data class

• Model application evaluation

application
Data-specific API interaction
lt
Data-specific rules
lt
lt
Platform basic sensors
System platform

• Application throughput and latency comparison
  with a combination of different data

29th November, 2005
2nd Middleware Doctoral Symposium _at_ Middleware
2005 Conference, Grenoble, France
16/23
17
lt interlude JMS clusteringgt
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro

• JMS specs put high demands on the message
  server
• JMS specs rich semantics, represent different
  types of messaging
• JMS clustering model shared persistent store

• not continuous availability
• idle servers waste of hardware resources

29th November, 2005
2nd Middleware Doctoral Symposium _at_ Middleware
2005 Conference, Grenoble, France
17/23
18
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro

• JMS clustering model back channel

• redundant networking
• complex system architecture
• waste of hardware resources

29th November, 2005
2nd Middleware Doctoral Symposium _at_ Middleware
2005 Conference, Grenoble, France
18/23
19
Evaluation
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro

• JMS translucent clustering evaluation
• JMS cluster based on group communication
• provides high levels of data redundancy
• translucency fits JMS rich semantics
• i.e. producers / consumers requests
• i.e. persistent / non persistent messages
• functional homogeneity JMS cluster design
• Blind replication test-bed (comparison
  baseline)
• JMS Server clients throughput and latency for
  different levels of translucency
• Scalability destination, throughput,
  connections

29th November, 2005
2nd Middleware Doctoral Symposium _at_ Middleware
2005 Conference, Grenoble, France
19/23
20
Summary
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro

• Transparent middleware approach important issue
• Dependability vs. performance conflicts
• Transparent replication
• Translucent architecture top-down and bottom-up
  models
• Novel translucent replication architecture
• Evaluation model application and real case
  scenario

29th November, 2005
2nd Middleware Doctoral Symposium _at_ Middleware
2005 Conference, Grenoble, France
20/23
21
Conclusions
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro

• Translucent middleware
• offers appropriate programming interface
  elements to the application
• pluggable modules (semantic rules) can be defined
  to expose the required level of granularity
• pluggable sensor can be defined for encapsulating
  management resources
• cross-layer interactions
• access middleware machinery according to
  application-specific requirements
• adjust the conflicts between dependability and
  performance turning them into trade-offs
• provide sets of solutions for application
  dependabiliy/performance trade-offs

29th November, 2005
2nd Middleware Doctoral Symposium _at_ Middleware
2005 Conference, Grenoble, France
21/23
22
Questions ?
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro
29th November, 2005
2nd Middleware Doctoral Symposium _at_ Middleware
2005 Conference, Grenoble, France
22/23
23
Thank you!
A Software Architecture for Translucent
Replication Etienne Antoniutti Di Muro
29th November, 2005
2nd Middleware Doctoral Symposium _at_ Middleware
2005 Conference, Grenoble, France
23/23