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Astronomical Data Analysis Software and Systems VII
ASP Conference Series, Vol. 145, 1998
R. Albrecht, R. N. Hook and H. A. Bushouse, e
Ö Copyright 1998 Astronomical Society of the Pacific. All rights reserved.
ds.
OPUS­97: A Generalized Operational Pipeline System
J. Rose
CSC: Computer Sciences Corporation, Inc.
Abstract. OPUS is the platform on which the telemetry pipeline at the
Hubble Space Telescope Science Institute is running currently. OPUS
was developed both to repair the mistakes of the past, and to build a
system which could meet the challenges of the future. The production
pipeline inherited at the Space Telescope Science Institute was designed a
decade earlier, and made assumptions about the environment which were
unsustainable.
While OPUS was developed in an environment that required a great
deal of attention to throughput, speed, e#ciency, flexibility, robustness
and extensibility, it is not just a ``big science'' machine. The OPUS
platform, our baseline product, is a small compact system designed to
solve a specific problem in a robust way.
The OPUS platform handles communication with the OPUS black­
board; individual processes within this pipeline need have no knowledge
of OPUS, of the blackboard, or of the pipeline itself. The OPUS API is
an intermediate pipeline product. In addition to the pipeline platform
and the GUI managers, the OPUS object libraries can give your mission
finer control over pipeline processing.
The OPUS platform, including a sample pipeline, is now available
on CD­ROM. That package, designed to be run on the Solaris operating
system, can help you decide whether OPUS can be used for your own
mission.
OPUS was developed in an environment which demanded attention to pro­
ductivity. A ten­fold increase in the volume of data was anticipated with the
new instrumentation to be flown on the Hubble, and the ground system required
a pipeline which could accommodate that load. OPUS has met these challenges.
A distributed pipeline system which allows multiple instances of multiple
processes to run on multiple nodes over multiple paths may seem like an opera­
tional nightmare. To resolve this, OPUS includes two pipeline managers: Motif
GUI applications which assist operations sta# in monitoring the system. The
Process Manager not only assists with the task of configuring the system, but
monitors what processes are running on which nodes, and what they are doing
currently. The Observation Manager provides a di#erent view of the pipeline ac­
tivities, monitoring which datasets are in which step in the pipeline and alerting
the operator when observations are unable to complete the pipeline.
1 rose@stsci.edu
344

OPUS­97: A Generalized Operational Pipeline System 345
The success of OPUS can be attributed in part to adopting a blackboard
architecture of interprocess communication. This technique e#ectively decouples
the communication process and automatically makes the entire system more
robust. Based upon the standard file system, OPUS inherits a simple, robust
and well­tested blackboard.
OPUS has been operational at the Space Telescope Science Institute since
December 1995, and has now been packaged 2 so that other missions can take
advantage of this robust, extensible pipeline system.
1. Fully distributed processing...
OPUS supports a fully distributed processing system. This means multiple
instances of a process are able to be run simultaneously without interference
from one another. In addition it can support a variety of processes, each a step
in the pipeline.
Moreover multiple pipelines, or paths, are supported. For example, at the
Space Telescope Science Institute it is necessary to operate a real­time pipeline
at the same time that a production pipeline is processing. And a reprocessing
pipeline may be simultaneously converting science images in the background.
In addition to several pipelines with identical processing steps, OPUS sup­
ports any number of distinct pipelines all running on the same set of processors.
Thus, in addition to the science pipelines, OPUS accommodates an engineer­
ing data pipeline, a separate pipeline for other non­science data, as well as an
interface to Goddard Space Flight Center for data receipt.
All pipelines are defined in simple text files. The pipeline path file defines
a set of network­visible directories on the shared disks. While one set of disks
is being used to process one kind of data, another set can be employed to pro­
cess a di#erent type of data. ASCII text files are the basis for configuring any
component of the OPUS environment. Adding an additional machine to the set
of nodes is accomplished by editing a text file: that node will immediately be
available to share the load.
The OPUS managers are uniquely suited to keep track of the environment.
The Process Manager keeps track of what is running where, while the Obser­
vation Manager is monitoring the progress of observations being processed in
any one of the pipelines. Multiple Observation Managers can each monitor their
own pipelines without interference from one another.
2. ...or a simple data pipeline
Even though OPUS was developed in an environment that required a great
deal of attention to throughput, speed, e#ciency, flexibility, robustness and
extensibility, it is not just a ``big science'' machine. The OPUS platform, our
2 http://www.stsci.edu/opus/

346 Rose
baseline product, is a compact 3 system designed to solve a specific problem in
a robust way.
OPUS is implemented as an automated pipeline, one which can start up
automatically, send exposures from task to task automatically, and monitor how
things are proceeding automatically. OPUS is designed to achieve a ``lights­out''
operation: data can enter the pipeline, be processed, then archived without
intervention.
The OPUS pipeline managers monitor the status of each exposure in the
system: how far it got in the pipeline, whether it failed and where it failed. The
GUI interfaces provide convenient tools to investigate problems, examine log
files, view trailers, and restart troubled exposures at any step in the pipeline.
The FUSE (Far Ultraviolet Spectrographic Explorer) team selected OPUS
for their pipeline even though they will be receiving only a moderate amount of
data that will processed on a single workstation. OPUS was chosen because it
frees the FUSE team to concentrate on the science and calibration issues which
are unique to their instrument.
By handling the mechanics of data processing, OPUS frees the scientists to
do science.
3. OPUS­97 platform
The OPUS platform is the baseline pipeline product. All communication with
the OPUS blackboard is handled by the platform; an individual process within
this pipeline need have no knowledge of OPUS, of the blackboard, or of the
pipeline itself.
OPUS can accommodate any non­interactive shell script. When there is
work to be performed by that script, OPUS will pass the name of the dataset to
be processed, the location of that dataset and other auxiliary datasets, as well
as other parameters required by the script.
Similarly the OPUS platform can wrap any stand­alone, non­interactive
executable which takes the name of the input dataset as a single argument. All
other information for that task is either passed by OPUS through environment
variables (symbols) or is obtained from the dataset itself.
OPUS is fully table­driven. To add another process to the OPUS pipeline
only requires the development of an ASCII text file describing the command
line arguments, the pipeline triggers, subsequent process triggers, and other
such control information.
Processes (or scripts) can be triggered in three ways: the most common way
is to allow the completion of one or more previous pipeline steps to act as the
process trigger mechanism. Another useful technique is to use the existence of
a file as the trigger. Alternatively one can use a time event to trigger an OPUS
process (eg: wake up once an hour).
3 The OPUS baseline system is less than 20,000 lines of code.

OPUS­97: A Generalized Operational Pipeline System 347
The OPUS platform is being distributed now on CD­ROM 4 for the Solaris
platform. This distribution comes with a sample pipeline which shows how to
set up the system and how to modify it to reflect your own needs.
4. An OPUS Pipeline
Where the OPUS platform is a generalized pipeline environment, it does not
provide the applications which handle mission­specific data. The OPUS team
at the STScI has a variety of tools and packages at hand to help build func­
tional telemetry pipelines. Packages to handle FITS files, keyword dictionaries,
database access, keyword population, message handling, and the like, form the
building blocks of a standard astronomical data processing pipeline.
Certainly the specific applications are not portable, but the experience of
the OPUS team in developing complete pipelines for Hubble and for FUSE can
be easily applied to other missions.
Is OPUS overkill for a small mission? No. First, OPUS is not a large
system. It is compact, designed to solve a specific problem in a robust way:
distributed processing with controlled monitoring. Second, OPUS does the con­
trolled monitoring. Telemetry processing does not have to be a labor intensive
task. OPUS relieves your talented engineering and science sta# to do more in­
teresting work. Third, OPUS exists. Your mission is to understand the science,
not to build pipelines.
Acknowledgments. The entire OPUS team at the Space Telescope Sci­
ence Institute was involved in the development of OPUS­97: Daryl Swade (CSC),
Mary Alice Rose (AURA), Chris Heller, Warren Miller, Mike Swam and Steve
Slowinski are all to be congratulated.
References
Rose, J., Choo, T.H., Rose, M.A. (1995) ``The OPUS Pipeline Managers'' in
ADASS V, pp311­314.
Rose, J. et al (1994) ``The OPUS Pipeline: A Partially Object­Oriented Pipeline
System'' in ADASS IV, pp429­432
Nii, H.P. (1989). ``Introduction'' in Blackboard Architectures and Applications,
Jagannathan, V., Dodhiawala, R., Baum, L., editors, Academic Press,
San Diego, CA, pp xix­xxix.
4 http://www.stsci.edu/opus/opusfaq.html