Concierge: Bringing OSGi (Back) to Embedded Devices

© 2013 IBM Corporation
Concierge: Bringing OSGi (Back) to Embedded
Devices
Jan S. Rellermeyer, IBM Research
Jan S. Rellermeyer
24 Sep 2013

Embedded Devices
 Typically fixed-function devices
 Limited user interface
 ISA
 OS
 Software typically closely tied to the hardware
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Image: www.eeweb.com

Embedded Devices Are Evolving
 We see a new class of embedded systems emerging
 Advanced processors
 Larger set of capabilities
 Enhanced user interface / user experience
 Open platforms for a software ecosystem
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Image: www.apple.com

Mobile Transforms Embedded Systems
Image: www.honeywell.com
Image: www.nest.com
Image: www.nikon.com
Image: www.apple.com

Continuous Platform Experience
5
Cloud
SoftwareStack
Embedded Device
Image: http://www.raspberrypi.org
ESSC

OSGi
 Dynamic Module System for the Java Runtime
 Original domain: Home Gateway
– Multiple software packages need to co-exist on the same machine
– Long-running software
– Periodic maintenance and updates requires
– Ideally with minimal downtime and no interruption of unrelated software packages
6
• Java on the Embedded Device
• Pros:
• bridges heterogeneity
• can run the same code in the cloud or on the device
• Cons:
• updates and maintenance

Module Management
 Traditional Java: The mystical class path
 java –cp commons-X.jar:foo.jar:bar.jar my.application.MainClass
• Which module contains the main class?
• What are the dependencies between foo.jar and bar.jar?
• What happens if bar.jar is upgraded to bar-1.01.jar?

OSGi – Module Layer
 Modules are called Bundles
– JAR files with additional metadata
 Runtime system: The Framework
– Lifecycle management
 Bundles implement isolation and locality
 Interaction between bundles is limited
– Shared code through package imports
– Inter-bundle calls through services
– Monitoring system state through events

The Lifecycle of a Bundle
 Management: Install / Start / Stop /
Uninstall bundles at runtime.
 OSGi keeps track of dependencies
 What happens if a Bundle is
uninstalled?
From the OSGi Core Specifications

The OSGi Framework
OSGi Framework
BundleA
Package 1
Package 2
Package 3
BundleB
Package I
Package II
Exported Package Exported Package
Private Package
Import
Export-Package: Package 1 Export-Package: Package I, Package II
Import-Package: Package 1
• Packages can be versioned
• OSGi encourages semantic versioning of bundles and packages

OSGi Services: Reducing Coupling
 Modules allow for a compositional approach to building applications
 But: Package dependencies are explicit.
– Limits the modularity!
 Solution: Services
– Idea: Separate the interface from the implementation
Interface
Implementation
Module
Module Module Service Service

The Service Registry
 The OSGi framework maintains a central service registry
 Bundles can register their own services and retrieve services provided by other
bundles
 Services can be registered with a set of properties
– Additional description of the service, can be used to model constraints or do
“best fit matching”
 No runtime overhead for using services after lookup!
Registry

OSGi Services
 Composition at runtime
 Loosely-coupled interaction through services
 The system is dynamic
13

14
Concierge
 Question: What is the (minimum) overhead of OSGi?
 My answer: Concierge
– OSGi R3 core implementation developed during my PhD at ETH
Zurich
– optimized for mobile and embedded devices, has a footprint of only
86kB
– People found the source code readable and understandable: 7
Java classes + 7 inner classes.
[J.S. Rellermeyer and G. Alonso: Concierge – A Service Platform for Resource-Constrained Devices. In:
EuroSys 2007].
Image: http://www.linksys.com

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Consistency across Platforms
iPAQ 3870
Linux Familiar 0.8
SA-1110 CPU
64 MB RAM
SableVM
Zaurus 5500G
Linux Embedix
SA-1110 CPU
64 MB RAM
Sun cvm
Nokia 9300i
SymbianOS
TI OMAP 1510 CPU
80 MB RAM
IBM J9
iPAQ 5550
Windows Mobile
PXA255 CPU
128 MB RAM
IBM J9
LinkSys NSLU2
Unslung
IXP420 CPU
32 MB RAM
JamVM

16
Performance influence of the final modifier

Example: The BUG Platform
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 Embedded Linux Device
 Runs Java (PhoneME) and OSGi
 Pluggable hardware
modules
 Registers OSGi services
 Applications are OSGi
bundles
Image: http://www.buglabs.com

OSGi R3
 OSGi R3: “unique” bundles and packages
19
my.bundle.one my.bundle.two
exports my.package
imports

OSGi R4
 OSGi R4: multiple versions, class spaces
 Fragments
 Require-Bundle
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my.bundle.one 1.0 my.bundle.two
exports my.package; version 1.0
imports
my.bundle.one 2.0
exports my.package; version 2.0

OSGi R5
 OSGi R5: generic requirements and capabilities
 Many hooks into the framework to manipulate the observed state
21
my.bundle.one 1.0
my.bundle.two
Provide capability foo.bar{a=10, b=[1,2,3]}
Require capability foo.bar filter=(!(a>10))

Generic vs. Optimized
22
Packages Bundles
Generic
Capabilities

Concierge goes Eclipse
 Targets:
 Full OSGi core R5 compatibility
 Keep a small footprint to work well on embedded devices
– Currently < 350kB footprint
 Remain “readable”
– Currently 9 classes
 Remain backwards-compatible
 Being a sandbox for innovation around OSGi
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Image: http://www.eclipse.org

Demo
 BeagleBone
 AM335x 720MHz ARM Cortex-A8
 256MB DDR2 RAM
 4GB microSD card
 runs Angstrom Linux Distribution
 Java SE Embedded 1.7.0_21-b11
 Concierge R5 alpha
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Image: http://www.beaglebone.org

REST Interface
 Designed for the cloud
 Very useful for embedded systems as well
 Examples
– GET http://my_host/framework/bundles/representations
– POST http://my_host/framework/bundles
– GET http://my_host/framework/bundle/5/state
– GET http://my_host/framework/services/(objectClass=org.osgi.*)/representations/
 This is work in progress (RFC 182)
 http://www.osgi.org/download/osgi-early-draft-2013-03.pdf
25

Location Transparency: Remote Service Invocation
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Juggle
 Model critical functionality as services
–Module with hardware-accelerated
service
–Co-Module with dynamically
accelerated service
 “Juggle” with the accelerators
27

Juggle Prototype System
 Xilinx Virtex-II Pro
 PPC 440 core, 300 MHz
 256 MB DDR SRAM
 Linux 2.6.35 (patched)
 JVM
–IcedTea Zero, IcedTea Cacao, or IBM J9
 OSGi Framework
– Concierge
 Juggle
– Adds support for loading and managing co-bundles
– Manages the FPGA and the reprogramming
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Image: http://www.xilinx.com

Evaluation
 PRR of about 16% of the chip real estate
 Reprogramming time: 11 – 25 msec.
(Literature: max. 30 msec)
 Switching the socket bridge: 3 msec.
 Initial load time for a hardware accelerated bundle: ~ 100 msec.
 Initial load time for a co-bundle: < 1sec
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TDES with hardware acceleration
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Concierge: Bringing OSGi (Back) to Embedded Devices

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