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 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 Container setToolBoxLoader(“atst.cs.ice.IceToolBoxLoader”); setToolBoxLoader(“atst.cs.jaco.JacoToolBoxLoader”); Component Event.post(eventName, eventMessage); Toolbox eventTool.post(getTimestamp(), appName, eventName, eventMessage); ICE Event Service Tool JacORB Event Service Tool

An Example: Log Service Component Log.warn(“M2 temp overload); Toolbox logTool.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 (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