Athena Developer Guide

Athena
Chapter 13 Framework services Version/Issue: 2.0.0
Chapter 13
Framework services
13.1 Overview
Services are generally sizeable components that are setup and initialized once at the beginning of the
job by the framework and used by many algorithms as often as they are needed. It is not desirable in
general to require more than one instance of each service. Services cannot have a “state” because there
are many potential users of them so it would not be possible to guarantee that the state is preserved in
between calls.
In this chapter we describe how services are created and accessed, and then give an overview of the
various services, other than the data access services, which are available for use within the Athena
framework. The Job Options service, the Message service, the Particle Properties service, the Chrono
& Stat service, the Auditor service, the Random Numbers service and the Incident service are available
in this release. The Tools service is described in Chapter 14.
We also describe how to implement new services for use within the Athena environment. We look at
how to code a service, what facilities the Service base class provides and how a service is managed
by the application manager.
13.2 Requesting and accessing services
The Application manager creates a certain number of services by default. These are the default data
access services (EventDataSvc, DetectorDataSvc, HistogramDataSvc,
NTupleSvc), the default data persistency services (EventPersistencySvc,
DetectorPersistencySvc, HistogramPersistencySvc) and the framework services
described in this chapter and in Chapter 14 (JobOptionsSvc, MessageSvc,
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