The ALMA common software: dispatch from the trenches

The ALMA Common Software (ACS) provides both an application framework and CORBA-based middleware for the distributed software system of the Atacama Large Millimeter Array. Building upon open-source tools such as the JacORB, TAO and OmniORB ORBs, ACS supports the development of component-based software in any of three languages: Java, C++ and Python. Now in its seventh major release, ACS has matured, both in its feature set as well as in its reliability and performance. However, it is only recently that the ALMA observatory's hardware and application software has reached a level at which it can exploit and challenge the infrastructure that ACS provides. In particular, the availability of an Antenna Test Facility(ATF) at the site of the Very Large Array in New Mexico has enabled us to exercise and test the still evolving end-to-end ALMA software under realistic conditions. The major focus of ACS, consequently, has shifted from the development of new features to consideration of how best to use those that already exist. Configuration details which could be neglected for the purpose of running unit tests or skeletal end-to-end simulations have turned out to be sensitive levers for achieving satisfactory performance in a real-world environment. Surprising behavior in some open-source tools has required us to choose between patching code that we did not write or addressing its deficiencies by implementing workarounds in our own software. We will discuss these and other aspects of our recent experience at the ATF and in simulation.