Improving Service Availability of Singleton Software Component: Challenges and Strategies

1. Improving Service Availability of
Singleton Software Component:
Challenges and Strategies
Yohanes Kuma and Reta Shiferaw

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› Current
architecture
Motivation

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Study
Ambition
Motivation

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Stateful
Singelton
Component
(SSC)
SSC- a single threaded stateful component responsible to handle
certain functionalities of Ericsson RBS architecture
Challenges

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› The SSC of Ericsson RBS have significantly long
session duration
› In addition to a kind of interaction where the SSC will
act as a server, SSC will also act as a client
› SSC should be responsive during switchover
challenges

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RQ1 - Is it possible to have controlled switchover
functionality for SSC in RBS to preserve component
functionality and state, and thus increase system
availability?
RQ2 - What changes are needed compared to the
current way of implementing SSC to better support
switchover?
RQ3 - What extra functionality needs to be added in SSC
to handle switchover?
Research questions

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› Qualitative research
– design patterns to ease switchover process
– session and state replication techniques, and object serialization
› Design research
Approaches

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Approaches---Reference
architecture

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› SUSE Linux Enterprise Server
› Enea LINX Interprocess Communication Platform
› Plab Messaging Library
› Signal Distributer Library
Approaches---Setting

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Replication States
System States
Results --- Prototype design
states

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Results --- switchover process

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› Serialization : the process of translating an
object into a format that can be stored/restored
› Four technologies investigated:
– Data Object Library
– Protocol Buffers
– Boost
– Cereal (the choosen one)
Results
Object serialization

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› C++11 header only serialization library
› Has different representation
❖compact binary encodings
❖XML
❖JSON
› 100% performance advantage over boost and
Protocol Buffers
› Easier to comprehend and extend
Cereal

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Cereal --code snapshot

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Cereal --code snapshot

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Cereal --code snapshot

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Results
Prototype design strategies
Name serving

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Results
Prototype design strategies
Service request handling

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Results
Prototype design strategies
Service response handling
› LINX only guarantees FIFO
ordered messages
› Message Order
Consistency with Sequence
Numbers
R1R1
R2R2
R3R3
G G
2
1
1
3
3
2
Preparation phase

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Results
Prototype design strategies
Service response handling

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System state
Results --- Prototype design
states

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› Correctness test via predetermining the expected
behavior during and after switchover process,
› Stress test of #Groups and #payload on
switchover process duration
› Stress test of #missed indication messages on
switchover process duration for synch purpose
› Stress test of #Groups on serialization and
deserialization duration
› Efficiency test on memory utilization during
serialization
Evaluation of the prototype

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correctness test

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Stress test

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Stress Test

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Time Effectiveness of serialization and
deserialization

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Efficiency test on memory utilization during
serialization

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➔Two additional Processes
➔Two additional Interface Units
➔~45 bytes memory per group during Se/Deserialization
➔Messages
◆ Switchover process management
◆ Transport serialized data
◆ Subscription and unsubscription for resource states
◆ Synchronization of missing indication messages
Discussion
(RQ2 & RQ3)
Added functionalities

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~1K LOC
~100 LOC
› ~5 LOC on Class definitions for Cereal
› Linking of Cereal Library
Discussion
(RQ2 & RQ3)
Added functionalities

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➔Switchover process duration grows linearly
with number of groups
◆ May change when tested with real product
environment
➔Cereal is efficient when compositional
object relations are serialized together
Discussion
performance

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Discussion
fault tolerance

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Future work-- suggested design
pattern

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conclusion
› Potential implications towards strategies for high availability

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