a software framework for the advanced technology solar telescope steve wampler

A software framework for the

Advanced Technology Solar

Telescope

Steve Wampler

What is ATST?

•7X photon collecting power

•Unvignetted light path

•Prime focus heatstop/occultor

•Integrated 1300+ actuator AO

•Rotating Coudé lab

•70TB/day collected, 5TB/day

delivered

•Haleakala, Maui, Hawaii

Advanced Technology Solar

Telescope

Observatory SW Trends

• Away from ‘custom’ toward:– Commodity hardware (PC), distributed systems

– Commodity OS (Linux, FreeBSD, etc.)

– Common Software infrastructure

– COTS/Community communication middleware

– Standard software models (tiered, separation of

technical and functional architectures, etc.)

– Common high-level models and architectures

Common Software

• Common framework for all observatory software– ALMA ACS is excellent example– ATSTCS draws from general ACS model

• Much more than just a set of libraries• Separates technical and functional architectures• Provides bulk of technical architecture through

Container/Component model• Allows application developers to focus on functionality• Provides consistency of use• System becomes easier to maintain and manage

Communication Middleware

• Avoids need to write communication infrastructure in-house– Less effort– Less in-house expertise required– Access to outside expertise– Benefit from wide-spread use

• Often provides rich set of features

• Supports actions required to run in a distributed environment

• Lots to choose from (both commercial and community)

What’s wrong with Middleware?

• 900-lb gorilla:– Promotes dependency on small set of vendors

– Hard to control direction

– Typically deeply integrated into common services

– Difficult to change once integrated (lots to choose from, but

once you choose, you’re stuck)

– Sometimes obsolete before deployment

– Too feature-rich (Kid-In-Candy-Store syndrome)

• Adopting standards (e.g. CORBA) instead of specific

packages can help, but:– Standards not particularly agile, often incomplete

– Can still get stuck as technology advances

ATST Common Software

ATST Containers and Components

ComponentsComponents

Container

Lifecycle control Service access

interfaces

Custom interface

User code

ATST Components

IRemote ILifeCycle

IController

Container Component Controller

IFunctional

IContainer IComponent

Technical InterfacesTechnical Interfaces

Functional InterfacesFunctional Interfaces• Narrow functional interfaces

– IComponent has just two commands: get, set– IController has six commands: get, set, submit, pause, resume, and cancel

• Controller implements “command/action/response” model– Actions execute asynchronously from command submission (no blocking)– Supports multiple simultaneous actions– Supports scheduled actions

• These classes implement technical interfaces, subclasses add functionality. e.g.

doSubmit, doAction

Many services available

Service Layers

• Service tools• Component-specific data

• All knowledge of service implementation isolated by the respective Service Tool

• Tool chaining keeps tools small and focused

• Uniform access from Components

• Designed for use, not implementation• Bridge between functional and technical

Containers/Components

Toolbox Loaders

Toolbox

Loader

Palate of Service Tools

Toolbox

Shared Private

Ex: Toolbox Loader

An Example: Event Service

ContainersetToolBoxLoader(“atst.cs.ice.IceToolBoxLoader”);

setToolBoxLoader(“atst.cs.jaco.JacoToolBoxLoader”);

ComponentEvent.post(eventName, eventMessage);

ToolboxeventTool.post(getTimestamp(), appName, eventName, eventMessage);

ICE

Event Service

Tool

JacORB

Event Service

Tool

An Example: Log Service

ComponentLog.warn(“M2 temp overload);

ToolboxlogTool.log(getTimestamp(), appName, “warning”, message);

Buffered DB

Log Service

Tool

Post

Log Service

Tool

Print

Log Service

Tool

• Three service tools chained

How well is ATSTCS working?

• Approach seems successful (early alpha-release supported both CORBA and ICE)– Choice of service tool has no impact on component

development – can select between CORBA/ICE at runtime– Already helped in unexpected ways (licensing conflicts)

• ICE/CORBA service tools easy to write:– Both similar architectures– Both align well with access helper models

• Less aligned services likely to be harder– Changes are well isolated at service tool layer, however

• 3rd party implementation of TCS simulation

• Developer code “simpler”

Ex: Controller Simulator

Event system performance

• Three dual-core machines (source, target, and event server), GbE network,

CentOS4

• Two versions of ICE: 2.1 and 3.2 (CORBA OmniNotify/TAO much slower)

• 1,000,000 events, ~120 bytes each

• All Java (JDK 1.6) code (C++ and Python currently much slower)

• Two service tools tested (unbatched and batched), now combined into a

single tool (per-event stream batching), both fully stable

Log service performance

• All dual-core machines (source, logdb server), CentOS4, GbE

• PostgreSQL version 8.2.4, JDK 1.6

• 500,000 messages, two sizes of payload

• end-to-end performance (client to database)

• Buffered and unbuffered service tools tested

– Multi-buffering to handle message spikes

But wait, there’s more…

• Toolboxes themselves can be chained, so higher-level application layers can delegate management of specialized services to ATSTCS (e.g. DHS header service and data distribution service)

• Service tool chains can be changed dynamically (DHS Quick-look Probe)

• Can help with system migration as software technology advances and to help integrate legacy systems:

– E.g. (carefully) chain ICE and CORBA tools together– Reduces effects of ‘big bang’ system upgrades when

core infrastructure changes