A middleware-neutral common services software infrastructure

Steve Wampler

National Solar Observatory

ICALEPCS’2005

What is ATST?

•7X photon collecting power

•Unvignetted light path

•Prime focus heatstop/occultor

•Integrated 1300+ actuator AO

•Rotating Coudé lab

•Hybrid enclosure

•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 Services infrastructure– COTS/Community communication middleware– Standard software models (tiered, separation of

technical and functional architectures, container/component (ala: .NET, EJB, CORBA CCM)

– Common high-level models and architectures

Common Services

• 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 (like .NET, EJB, and CORBA’s CCM)

• 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

• Adopting standards instead of specific packages can help, but:– Standards not particularly agile– Can still get stuck as technology advances

ATST Common Services

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• Bridge between functional and technical

Containers/Components

Toolbox Loaders

Toolbox Loader

Palate of Service Tools

Toolbox

Shared Private

An Example: Event Service

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

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

ComponentEvent.post(eventName, eventMessage);

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

ICEEvent Service

Tool

JacORBEvent Service

Tool

An Example: Log Service

ComponentLog.warn(“M2 temp overload);

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

Buffered DBLog Service

Tool

PostLog Service

Tool

PrintLog Service

Tool

• Three service tools chained

How well is ATSTCS working?

• Approach seems successful (demonstrated by alpha release of Common Services with ICE and CORBA versions of services)– Choice of service tool has no impact on component

development– Already helped in unexpected ways

• 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

But wait, there’s more…

• Service tools can be changed dynamically• Can customize tool sets on a per Container or even

per Component case• ‘Easy’ to compare effects of middleware choices• Can more easily pick different services from

different middleware• Can help with system migration as software

technology advances and to help integrate legacy systems:– E.g. chain ICE and CORBA tools together– Avoids need for ‘big bang’ system upgrades