Abstract
The Conditions Database (CondDB) of the LHCb experiment provides versioned, time dependent geometry and conditions data for all LHCb data processing applications (simulation, high level trigger, reconstruction, analysis). The evolution of CondDB and of the LHCb applications is a weakly-homomorphic process. It means that compatibility between a CondDB state and LHCb application state may not be preserved across different database and application generations. More over, a CondDB state by itself belongs to a complex three-dimensional phase space which evolves according to certain CondDB self-compatibility criteria, so it is sometimes difficult even to determine a self-consistent CondDB state. These compatibility issues may lead to various kinds of problems in the LHCb production, varying from unexpected application crashes to incorrect data processing results. Thus, there is a need for defining a well-established set of compatibility criteria between mentioned above entities, together with developing a compatibility tracking system which will help to discover incompatibilities avoiding their negative consequences. This paper describes an attempt to approach this goal in the frame of the graph theory which allows to formalize elegantly the task of compatibility tracking.
Highlights
I N the current LHCb [1] computing model [2] compatibilities of LHCb data processing applications and LHCb Conditions Database (CondDB) [3] states are not tracked and are managed in a manual and very limited way
This may lead to a diverse set of application execution failures in the LHCb production when LHCb software evolution passes non-homomorphic mutation phases. Even this phenomenon may seem to be very annoying by itself, and it is such in the LHCb collaboration running into a thousand of members. It is not the worst scenario: a danger always exist that a wrong combination of CondDB and application states may be used in production in which case the results of the LHCb application execution might not be entirely correct
To process the tasks listed at the beginning of this section the compatibility tracking system (CTS) will have to “talk” to a graph described in the previous subsection
Summary
I N the current LHCb [1] computing model [2] compatibilities of LHCb data processing applications and LHCb CondDB [3] states are not tracked and are managed in a manual and very limited way. This may lead to a diverse set of application execution failures in the LHCb production when LHCb software evolution passes non-homomorphic mutation phases. Even this phenomenon may seem to be very annoying by itself, and it is such in the LHCb collaboration running into a thousand of members. Lowing a definition of the compatibility criteria (Section III), we will describe a design of the compatibility tracking system (Section IV)
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