Approaches to Ultra Long-Term System Maintenance · 2017-12-14 · Backporting I Leverage LTSI...
Transcript of Approaches to Ultra Long-Term System Maintenance · 2017-12-14 · Backporting I Leverage LTSI...
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Corporate Technology
Approaches to Ultra Long-TermSystem Maintenance
Embedded Linux Conference Europe 2016
Prof. Dr. Wolfgang MauererSiemens AG, Corporate Research and TechnologiesSmart Embedded SystemsCorporate Competence Centre Embedded Linux
Copyright c© 2016, Siemens AG. All rights reserved.
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Overview
1 Introduction
2 Aspects of Long-Term MaintenanceArchitectural CharacteristicsThreats and Risks
3 Technical AspectsPayload SoftwareDeveloping, Building and TestingIn-Field Strategy
4 Backporting & ProcessesBackporting: Conceptual and Technical Issues
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Outline
1 Introduction
2 Aspects of Long-Term MaintenanceArchitectural CharacteristicsThreats and Risks
3 Technical AspectsPayload SoftwareDeveloping, Building and TestingIn-Field Strategy
4 Backporting & ProcessesBackporting: Conceptual and Technical Issues
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Introduction 0
Disclaimer
Many statements: Extremely obviousRealisation: Quite remote for many problematic appliancesQuantification: Astonishingly hard. . .
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Introduction I
Consumer Electronics
Mobile Phones, Notebooks,Tablets, . . .Entertainment systems(Radio, TV, DVD/BlueRay, . . . )Ovens, Washing Machines,Home Control/Automation
Industrial Systems
Medical devicesComputed tomography,X-Ray Imaging,Ultrasound, . . .
InfrastructureGas, Power, Water supplyPowerstations andtransformersTraffic lights, park spacemanagement
MobilityPlanes, trains,automobiles, mars rovers,space stations
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Introduction II
Fundamental questions
Is long-term maintenance reasonable/doable?System architecture for LTM?
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Innovation Cycles I
Lifespans
Consumer devices: 2-5 yearsMobility: 5-20 yearsIndustrial: 10-30 yearsInfrastructure: 30-80 years (and up!)
All domains: Linux, of course!
Long-life requirements not restricted to industrial appliances!IoT, smart home, connected devices: Longevity requirementspervade everyday devicesShort lifespans: Exception, not rule!
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Innovation Cycles II
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Innovation Cycle III
Fundamental Questions
Risks and benefits ofupdates?How to restrict updates to(isolated) areas?How to avoid updates?
Beyond components
Questions not addressed bysimply using LTScomponents/distrosLTM: Architectural issueLTM: Mindset issue
Some field observations/bogus assumptions
All components can be upgraded in-field 7
Updates fix more problems than they create 7
Upstream integration always reduces maintenance effort 7
Long-term component versions solve maintenance problems 7
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Innovation Cycle III
Fundamental Questions
Risks and benefits ofupdates?How to restrict updates to(isolated) areas?How to avoid updates?
Beyond components
Questions not addressed bysimply using LTScomponents/distrosLTM: Architectural issueLTM: Mindset issue
Some field observations/bogus assumptions
All components can be upgraded in-field 7
Updates fix more problems than they create 7
Upstream integration always reduces maintenance effort 7
Long-term component versions solve maintenance problems 7
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Outline
1 Introduction
2 Aspects of Long-Term MaintenanceArchitectural CharacteristicsThreats and Risks
3 Technical AspectsPayload SoftwareDeveloping, Building and TestingIn-Field Strategy
4 Backporting & ProcessesBackporting: Conceptual and Technical Issues
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Appliance Architecture
Long-term maintenance vs. periodic re-building
Fixed (trusted) ↔ arbitrary payload softwareIsolated ↔ universally accessibleHardware stability ↔ varianceFixed hardware ↔ extensibility (e.g., USB)Verification and safety requirementsCost sensitivity (core payload inside virtual environments?)
Software aspects
System base softwarePayload software + architecture
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Appliance Architecture
Long-term maintenance vs. periodic re-building
Fixed (trusted) ↔ arbitrary payload softwareIsolated ↔ universally accessibleHardware stability ↔ varianceFixed hardware ↔ extensibility (e.g., USB)Verification and safety requirementsCost sensitivity (core payload inside virtual environments?)
Software aspects
System base softwarePayload software + architecture
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Appliance Architecture
Long-term maintenance vs. periodic re-building
Fixed (trusted) ↔ arbitrary payload softwareIsolated ↔ universally accessibleHardware stability ↔ varianceFixed hardware ↔ extensibility (e.g., USB)Verification and safety requirementsCost sensitivity (core payload inside virtual environments?)
Software aspects
System base software: Little/no controlPayload software + architecture: Full control ⇒ LTM Focus!
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Threats and Risks
What should LTM prevent in your case?
Device stops workingDevice faults cannot be repaired/debuggedDevice can be influenced from outsideDevice does not meet changed expectations (functionality,interoperability, . . . )
Response catalogue
Ignore issues (can be reasonable, on rare occasions)Replace device (HW + SW; component)Modify SW
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Threats and Risks
What should LTM prevent in your case?
Device stops workingDevice faults cannot be repaired/debuggedDevice can be influenced from outsideDevice does not meet changed expectations (functionality,interoperability, . . . )
Response catalogue
Ignore issues (can be reasonable, on rare occasions)Replace device (HW + SW; component)Modify SW ⇐ case of interest
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Outline
1 Introduction
2 Aspects of Long-Term MaintenanceArchitectural CharacteristicsThreats and Risks
3 Technical AspectsPayload SoftwareDeveloping, Building and TestingIn-Field Strategy
4 Backporting & ProcessesBackporting: Conceptual and Technical Issues
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Payload Software
Software Engineering Considerations
Deliver maintainable software/architecture in the first placeMinimise cross-cutting issuesHarmonise technical and social organisationMeaningful and reproducible history
Think three times before connecting systems to networks; thenthink three more times“Translator” with domain and (base component) communityknowledgeMake components (run-time) replaceable; prefer userland tokernel
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Payload Software
Software Engineering Considerations
Deliver maintainable software/architecture in the first placeMinimise cross-cutting issuesHarmonise technical and social organisationMeaningful and reproducible history
Think three times before connecting systems to networks; thenthink three more times“Translator” with domain and (base component) communityknowledgeMake components (run-time) replaceable; prefer userland tokernel
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Development & Building I
Reproducible Builds
Produce binaries. . . 20 years after initial launchPayload application + modifiable system componentsPreserve base component binaries
Documentation of (seemingly trivial) details essentialDocumentation availability (hardcopy is a serious alternative)Avoid custom build systems
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Development & Building I
Reproducible Builds
Produce binaries. . . 20 years after initial launchPayload application + modifiable system componentsPreserve base component binaries
Documentation of (seemingly trivial) details essentialDocumentation availability (hardcopy is a serious alternative)Avoid custom build systems
Source Code
Availability of source code + history (e.g., Bitkeeper. . . )Component states + local provision of dependenciesIncludes build infrastructure!
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Development & Building I
Reproducible Builds
Produce binaries. . . 20 years after initial launchPayload application + modifiable system componentsPreserve base component binaries
Documentation of (seemingly trivial) details essentialDocumentation availability (hardcopy is a serious alternative)Avoid custom build systems
Tool Chain
Cross-Building: (subtle) dependencies!Isolate build environment in VM (strict freeze!)Bugs in ancient toolchain: Payload SW workaroundsEclipse etc.: harder. . . 7
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Development & Building II
Component Selection and Integration
Consider cost of librariesDynamically changing dependencies (version requirement specsoften unreliable)Changes in components⇒ (silent) breakage in library
Distinguish between prototype and deliverableExperiment with 17 machine learning algorithmsDeploy one (+ rewrite)
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Development & Building II
Development prior to market release
Develop against latest mainline state (rebasing preferred)Avoid vendor BSPs. Board support essential, not BSPs!
Only chance: Prior to purchasing 1.8× 1023 units
System changes: Upstream first policyAvoid component modifications (socio-technical congruence)
Especially for features useless for upstream
Minimise divergence between upstream state and product atrelease time
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Development & Building III
Five Recommendations
1 Avoid complex development environments and generated code2 Avoid web technologies3 Use convenience libraries judiciously4 Avoid integration/consolidation; delegate
communication/networking to separate entities5 Document and automate excessively
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Options for post-release development
Rolling Development
Continuous updates of(selected) base componentsUncouple progress fromdistribution (e.g., after eol)Detect issues early,re-invent distribution wheel
Distribution schedule
sudo apt-get upgrade
Requires support bydistribution!
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Options for post-release development
System schedule
Update in appliance-specificintervals (periodic orirregular)Combine disadvantages ofdistribution and continuousupdates
Invariant base system
Don’t update base systemPayload applicationdevelopment onlyRequires (extremely) smallattack surface/virtualisedbase system
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Outline
1 Introduction
2 Aspects of Long-Term MaintenanceArchitectural CharacteristicsThreats and Risks
3 Technical AspectsPayload SoftwareDeveloping, Building and TestingIn-Field Strategy
4 Backporting & ProcessesBackporting: Conceptual and Technical Issues
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Backporting I
Leverage LTSI kernel
LTSI support period: Comprehensive coveragePost-LTSI: Backport only
Critical issues re/ attack surfacesOrthogonal drivers/componentsFeature not required during first 5 years⇒ unlikely required in nextdecade(s)Major change required (debugging, tracing etc.): Time for newrelease. . .
Backport patch stack
Organise backports in proper orthogonal patch stackRebase! Living organism, not code dump
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Backporting II: What and when to backport
1.) What to backport
Most upstream changes donot require back-portingSelection crucialSelection criteria differdepending on use case
Approaches
Keyword filtering (possiblefor well-tended projects)Content/file/path basedfiltering (tremendous volumereduction)Manual review + long-termexpert involvementnecessary
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Backporting II: What and when to backport
2.) When to backport
ProactivelyAfter incidents/bugs
Simple criterion
# incidents > # backportregressionsHistorical data: Noconclusive evidenceExpert assessment required
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Backporting III
The human touch
Determine when no action is requiredNotify users/customers
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Backporting IV
Goal: Simplify patch selection for everyone
Fully automatic approach: unrealisticAvoid duplicated manual efforts
Wishlist: Improvements
Maintenance classes (for patches), consistent across projectsCurrent schemes dating back to 70ies⇒ survey!
Applicability range (releases) annotationWide-spread use of automated approaches (backwards integration,testing)
Extend use of semantic vs. text-based modifications
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Summary
LTM best practices: Similar to proper (OSS-style) softwaredevelopmentSystem and application architecture: crucialLTM: not rocket science, but still more art than science –quantitative data required!
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Thanks for your interest!
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