Application d evelopment using the ALMA Common Software

SPIE 2006 – 6274-06

Application development using the

ALMA Common Software

G.Chiozzia, A.Caproniae, R.Ciramie,P.Di Marcantonioe, D.W.Fugated, S.Harringtonb, B.Jerama, M.Peskoc, M.Sekoranjac,

H.Sommera, V.Wanga, K.Zagarc aESO bNRAO cCosylab dU.Calgary eINAF-AOT

[email protected]

2SPIE 2006 – 6274-06 ALMA Common Software

Contents

• What is ALMA? Status?

• What is ACS?

• Where are we?

• Main features

• Platforms

• Looking back: considerations and lessons learned

• Projects and community

• Conclusion

• Free software• Asynchronous communication• Multithreading and distributed applications• Components and containers• …more in the paper


The ALMA project

• 50x12m antennas

• 4x12m antennas optimized for total-power (Japan)

• Compact array of 12x7m antennas for higher sensitivity to broad, low-surface brightness features (Japan)

• Antennas can be moved to ~185 different pads.

• Maximum baselines from 150m to 18km, resolutions from 1” to <0.01” at 850 µm.


Sensitivity and Angular Resolution


OperationSupport

Facility (OSF)

ALMA Sites in Chile

Antenna Operations Site (AOS)

Santiago Central Office (SCO)


Chile, Chajnantor plateau - 5000mChile, Chajnantor plateau - 5000m

Chile, Chajnantor plateau - 5000mChile, Chajnantor plateau - 5000m


ALMA AOS Technical Building, Apr 2006


ALMA Operation Site Facility (2900m – Atacama desert)


ALMA Operation Site Facility today


Antenna’s construction timeline

• First antenna delivered on site in Q1 2007.

• Further antennas coming from Q4 2007 with new antenna every 2 months.

• First science: end of 2009.

• Full completion: 2012.


ALMA Computing

• Large but extremely distributed team

• 40 Full Time Equivalent for whole E2E sw

=> Total development effort to 2011 ~280 FTE-years

• Staff in 14 Institutions Europe/North America/Japan


What is ACS?

ACS is a software infrastructure for the development of distributed systems based

on the Component/Container paradigm

• end-to-end: from data reduction to control applications• common application framework and design patterns, not

just libraries• well tested software that avoids duplication• make upgrades and maintenance reasonable• common development environment and tools


Where are we?

• Developed for ALMA and used by several other projects.• ACS is based on a kernel of software contributed by

cosylab and developed for the ANKA Synchrotron. Our collaboration started in Trieste at ICALEPCS 1999.

• ½ of allocated development effort spent until now• Total allocated ~30 man years + additional external

contribution (~10).• 10th release• Extensively used in the field:

– ALMA Test Interferometer and labs– ALMA software integrations– Other projects


Main Features

• ACS provides the basic services needed for object oriented distributed computing. Among these:– Transparent remote object invocation– Object deployment and location based on a

container/component model– Distributed error and alarm handling– Distributed logging– Distributed events

• The ACS framework is based on CORBA and built on top of free CORBA implementations.


Supported Platforms

• Operating system: Linux, RH-E + other flavours

• Real-time: RTAI and VxWorks

• Languages: C++, JAVA, Python

• CORBA middleware: TAO (& ACE) (C++), JacORB (Java), Omniorb (Python), CORBA services.

• Embedded ACS Container: PC104, Debian, 300Mhz Geode, 256MB RAM, 256 MB flash (CosyLAB microIOC)


LGPL and free software

• The strategy to provide common features to our users is:– Use as much as possible open-source tools, instead of implementing

things. • Do not reinvent the wheel• Reuse experience of other projects• Do not pay for licenses• Support from user’s community

– Identify the best way to perform a task among the possibilities

– Wrap with convenience and unifying APIs• ACS is distributed under LGPL license• Free software has also drawbacks:

– Fast lifecycle and support only of the newest– Free/commercial support– Documentation not as good as commercial products


Asynchronous communication

• ACS provides 4 ways to communicate between Components:– Synchronous method calls– Asynchronous method calls (callbacks)– Notification channel (publisher-subscriber)– Bulk data (hi-performance streaming, 60

Mbytes/s)


Notification channel usage

• Notification Channel has been used much more than expected to:– Synchronize subsystems: synchronization events– Publish data to multiple subscribers, not known a priori

• Preferred to callbacks because easier to implement• Very easy to use: evolution of ACS implementation

classes, coding conventions and tools• Drawbacks:

– more difficult to keep track of dependencies– Circular dependencies make a system more fragile

• Stick to unidirectional dependencies!Callbacks can help reversing dependencies.


Multithreading and distributed applications: the problems

• Component based systems like ACS are intrinsically:– Highly distributed– Asynchronous and multithreaded

• Methods can be called at any time, in parallel to the same or other methods.

• Developers need to be well aware of concurrency issues

• Debugging is more problematic than with single threaded applications


Multithreading and distributed applications: the solutions

ACS addresses these problems by means of:• Threading management classes• Centralized logging• Distributed error handling• Dynamic loading/unloading of Components• Component’s simulation• Tools for automatic regression tests

involving distributed Components


Components and Containers

• In recent releases we have improved decoupling of Components and Containers:– Container services– Dynamic components– Tasks

• Configuration of the runtime system is being re-discussed. We need better tools to keep aligned the configuration of the various ALMA deployments

• We have started concentrating on the deployment of Containers: requirements form pipeline and offline subsystems.


ACS installations and projects


The ACS community

HPTHexapod Telescope(Germany → Chile)

SardinianRadioTelescope(Italy)

OAN 30m (Spain)

ALMA(Chile)

ANKA (Germany)

APEX (Chile)


Conclusion

• Core concepts are now very stable. • Most packages are implemented, but not 100%• Most of the work comes now from change requests and feedback and

not from long term planning items• ACS is significantly improving in stability, usability and global

consistency.• Analysis of the applications developed and of the feedback from the

developers tells us what is good, what is bad and how to improve.More in the paper!

Having a user’s base in addition to our main project has provided important feedback,

cross-fertilization of concepts and ideas and contributed to software quality


Questions (& Answers)

http://www.hq.eso.org/projects/alma/http://www.eso.org/projects/alma/develop/acs

6267-02 The Atacama Large Millimeter Array: overview and status

6274-06

Application development using the ALMA common software

6274-07 Integrating the CERN laser alarm system with the ALMA common software

6274-45

Time synchronization within the ALMA software infrastructure

6274-54 Bulk data transfer distributer: a high performance multicast model in ALMA ACS

SC-644 Course: An Introduction to Scalable Frameworks for Observatory Software Infrastructure

6267-47 Phase correction studies for ALMA,

6271-14 System engineering in the ALMA project,

SPIE Papers on ALMA/ACS


Reserve slides


Observing in different bands

• 10 Frequency bands coincident with atmospheric windows have been defined.

• Bands 3, 6, 7 and 9 will be available from the start.

• Bands 4, 8 and 10 will be built by Japan.

• Some band 5 receivers built with EU funding.


Highlights of the Last Two Years

New in ACS for:

• developers to use in their code: libraries, convenience classes, utilities to improve the quality of the code

• test/integration/administrators, transparently from application code (i.e. in principle transparent to Component developers)


Component Container Evolution/Cleanup

• Container Services– Full separation between

Container and Container Services

– Cleaner interfaces– Easier to replace Container

implementation– The most important services

provided now by the ContainerServices are…

• Component life cycle– Plain instantiation of

Components not sufficient– Standard lifecycle state

machine introduced for the Container to manage Components

lifecycleinterface:init()cleanUp()

container

Com

p

Com

p

functionalinterface:observe()

container service interfacegetComponent(“CompB”);Logger getLogger();


Master Component

• ALMA subsystems interact with the Executive.• Executive treat all in the same way.

Lifecycle for subsystems, not only components

• Fits smoothly into acs concept: - each subsystem needs a mastercomponent - it is a component with a specific interface - ACS defines the underlying state machine

• Implementation:

- a generator (using open-architectureware) maps UML to state machines- generator creates convenience base classes - state machine has been refined in a couple of design iterations

• The introduction of the Master Component has been very effective.

• Cost of prototype generator not higher than cost of developing the MasterComponent in code


Event Handling and Notification Channel

• Events are widely used in ALMA for synchronization and asynchronous, *-to-* communication.

• Decoupling of Consumers and Suppliers• Very easy interface:

– Supplier classes– Consumer classes

• Contract based on IDL data structures.• Strong naming conventions and

checking tools• Administrative interface• Quality of service

ALMA Operator

(Java)

CAN bus devices (C++)

ALMA prototype antenna at the ATF

High-level Usage of ALMA Events

Secured Host for CORBA

Notification and Naming

ServicePipeline

processes(Python)

Observation Scheduler

(Java)

Astronomer Consuming

ALMA Events as

They Occur

CORBA Notification

Service Running On

an Unsecured

Server

Telescope Calibration

(C++)


Threading Support

• Many Components have a multi-threaded structure

• Management of threads was a source of problems

• Developed easy-to-use threading classes:– Override a run() method– Use the thread manager

• Based on ACE Threads in C++, concurrent library in Java

Component

ThreadManager

create<ThreadClass>()add()destroy()suspendAll()resumeAll()terminateAll()

11

Thread

suspend()resume()terminate()onStart()onStop()

0..n

0..1

ControlLoopThread

onStart()runLoop()onStop()

OneShotThread

onStart()run()onStop()

0..n

0..1

1


Concurrency patterns

• Concurrent execution is allowed.Access to resources is protected.

• The newly invoked request shall be rejected• The newly invoked request shall supersede

the old one• The newly invoked request is queued and

executed after completion of the previous one


A change in paradigm!

Real-time Support

• VxWorks → TICS• Entire LCU in real-time OS• ACS provides complete

Container/Component in real-time environment

• Support will probably remain for other projects (VLT)

• RTAI → ALMA• RT Kernel inside Linux• Component not real-time ↔

small time-critical functions in Kernel.

• Less code in real-time, but more complex to debug

• ACS provides easy:– Communication with kernel

modules– Logging from kernel modules– Kernel module management


Bulk Data Transfer

• Requirements from the correlator:– 64 MB (megabyte)/sec

• Based on CORBA A/V streaming service

• TAO C++ implementation

• Very easy interface, based on our use cases

• No CORBA A/V visible

Achieved Performance• Gigabit P2P Ethernet• BD throughput around 800

Mbits/s (~100 MB/s) requirements fulfilled

• CORBA throughput around then 500 Mbit/s (~ 55 MB/s)

• Estimated gain in the throughput around 30%


Simulation

• Why simulation?– Distributed development

– Features or entire subsystems not yet available

– Test a subsystem in isolation

• Simulation of Components from IDL interface spec.

• Dumb default or “intelligent” simulation

SPIE 2006 – 6274-06 ALMA Common Software

CERN Laser

ACS Alarm System: LaserFeasibility prototype to re-use

CERN Laser Alarm System

Keep the same API

Reuse the LaserAlarm Console

ACS Component/Cont

ainer replaces J2EE

acsjms implements jms for ACS on top

of Notification Channel

IDL interfaces replace EJB interfaces

Reimplementation

of Laser interfaces

The challenge: reuse a complete subsystem/service in a verydifferent software infrastructure


Tasks and Parameters

• ACS is used in ALMA also as data reduction infrastructure framework• Requirement:

data reduction to be started as a stand-alone process.A program which starts-up, performs processing and shuts down.

• Implementation:– Stand alone executable– Static container– Works with and without ACS suite

• Input parameters are complex data sets:– Parameter set definition (xml)– Parameter set instantiation (xml)– Validation – Parsing


GUIsA LabView

prototype has been

implemented

ACS Supports ABeans development with an

Eclipse plug-in

Some projects are using Qt

Different projects and differentsubsystems have different requirements!


Performance and Benchmarking

• ACS has performance requirements to satisfy

• Changes to code and upgrade of external libraries can affect performance

• Created performance measurements and reporting framework

• Performance of Component to Component communication, notification channel, logging system…

http://www.eso.org/~almamgr/AlmaAcs/Performance/BenchmarkDoc/


Performance

1471

2049

996

1659

2105

1065

0 0

125

981

1133

334

546

2013

9

1000

0 26

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500

1000

1500

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cpp py java cpp py java

Event Channel Throughput (100 bytes)

Average Throughput

Best Throughput

Worst Throughput

0

5000

10000

15000

20000

25000

Logs per second

AverageThroughput

BestThroughput

WorstThroughput

C++ Logging

10 bytes

25 bytes

100 bytes

1000 bytes

5000 bytes

Average C++ throughput: 1500 event/s (100 bytes)

Average C++ throughput: 3500 event/s (100 bytes)

Documents

Application d evelopment using the ALMA Common Software